UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION CIRCULAR No. 238 April, 1922 THE APRICOT IN CALIFORNIA By W. L. HOWARD The number of apricot trees in California in 1920, as reported by county assessors,* amounted to 3,339,716 bearing and 1,325,300 non- bearing, or a total of 4,665,016 trees young and old. Counting seventy- five trees to the acre, this would amount to 62,200 acres. In April, 1921, the Prune and Apricot Growers' Association estimated the total com- mercial acreage in the state to be 55,365 acres, but these figures did not include home orchards or small plantings in places remote from orchard centers. The actual cash returns to the growers for apricots sold for the year 1919 (175,000 tons), amounted to $14,000,000 and for 1920 (115,500 tons), to $9, 775,000. f These figures are based on an average price of $80.00 per ton in 1919 and $85.00 in 1920 for fruit of all grades. That the estimates are conservative is evidenced by the fact that in 1920 the canneries, which used the bulk of the crop, paid from $100.00 to $110.00 a ton for fruit as small as fourteen and even sixteen to the pound. Apricots are grown in Oregon, Washington, Idaho, Utah, Colorado, Arizona, New Mexico, Kansas, and even New York. No state but California produces them commercially in sufficiently large quantities to affect prices in the principal markets of the country. The U. S. Census of 1910 reported that 96.4 per cent of all the apricots grown in the United States were produced in California. Apricots are profitable only in regions where spring frosts do not kill the buds, flowers or young fruit, and where there is freedom from summer rains, which favor the development of brown rot at ripening time. The chief limiting factor is the frost hazard. The advent of numerous canneries handling apricots, coupled with a strong fresh-fruit cooperative association and the high prices pre- vailing in 1919 and 1920, greatly stimulated the planting of apricot trees all over the state. The planting was particularly heavy in the Santa Clara Valley, the Aromas section of Monterey County, and on * Report of California State Board of Equalization for 1919-1920. t California Crop Report, 1920, Appendix to Monthly Bulletin, California Department of Agriculture, December, 1920. J UNIVERSITY OF CALIFORNIA EXPERIMENT STATION the rolling lands or so-called "foothills" surrounding the Pajaro Valley in Santa Cruz County. Southern California, especially River- side and Los Angeles counties, shows a large increase in acreage of this fruit. Seedling apricots were grown in California as early as 1792 at the Santa Clara Mission. Named varieties, introduced from Europe, were first planted by American settlers some time previous to 1850. Apricots are grown for the fresh-fruit market, for canning, and for drying. The early fruit for eastern shipment is produced chiefly in the Imperial Valley, near Vacaville, and at Winters in the Sacramento Valley. Later in the season, apricots as fresh fruit are shipped from the Sacra- mento River region, and also from the San Joaquin and Santa Clara valleys. Apricots for canning are produced mainly in the coastal valleys and the San Francisco Bay region, and for drying purposes, in the San Joaquin, Sacramento, and other interior valleys. The following summary in Table I will give a good general idea of the quantities of apricots marketed fresh, dried, and in cans for the years 1915-1920. TABLE I Summary of Apricots Marketed in California for the Years 1915 to 1920, Inclusive (From California Fruit News) Canned, Dried, Fresh, Date cases tons cars 1915 981,190 19,500 329.25 1916 1,327,770 11,000 289.5 1917 2,356,553 15,500 403.0 1918 2,233,314 15,000 440.75 1919 4,395,204 15,500 419.5 1920 3.312,020 *10,000 312.0 The major portion of the early fresh fruit sold went to the eastern markets. "With improved methods of packing that have come under the recent fruit standardization laws, it is not probable that the fresh -fruit markets of the east w r ill ever become overstocked, because the areas where early apricots can be successfully grown are relatively limited. Beginning about the year 1916, the demands of the canneries have steadily reduced the amounts of apricots dried annually. In the coastal region and the districts adjacent to San Francisco Bay, the leading variety, the Blenheim, is grown almost exclusively for canning, only the lower grades being dried. In the interior valleys even the Royal, the premier drying variety, has been sent to the canneries in large quantities for the past four or five years. * 1920 figures not final. Circular 238] THE apricot in CALIFORNIA APRICOT DISTRICTS Apricots were reported as growing in all but seven of the fifty-eight counties of the state in 1920. One of these counties is the city of San Francisco, and the other six are in the high Sierras, where the altitude makes the spring frost hazard too great for such an early blooming fruit. Table II shows the number of bearing and non-bearing trees in each of the counties in the spring of 1920, and also the total number in 1909. TABLE II Number of Bearing and Non-bearing Apricot Trees in the Various Counties of California in 1920. Also Total Number Bearing and Non-bearing in 1909 (1920 statistics from Rept. Cal. State Board Equalization for 1919-20; 1909 figures from U. S. Census for 1910) Bearing, Non-bearing, Total No. Total No. County 1920 1920 Trees, 1920 Trees, 1909 Alameda 242,600 3,000 245,600 270,461 Alpine 6 . 6 7 Amador 1,365 60 1,425 1,197 Butte 3,060 4,230 7,290 9,900 Calaveras 2,000 100 2,100 672 Colusa 4,000 6,000 10,000 4,420 Contra Costa 49,000 3,000 52,000 38,812 Del Norte El Dorado 750 750 503 Fresno 10,480 10,480 186,823 Glenn 2,000 4,000 6,000 6,830 Humboldt 250 300 550 235 Imperial 7,580 4,260 11,840 1,922 Inyo 342 Kern 260 275 535 33,573 Kings 182,900 79,100 262,000 124,007 Lake 2,000 150 2,150 1,463 Lassen 400 400 800 70 Los Angeles 65,636 46,773 112,409 122,769 Madera 15,638 5,549 21,187 9,408 Marin 2,000 500 2,500 1,689 Mariposa 200 200 233 Mendocino 4,220 300 4,520 187 Merced 18,000 33,000 51,000 7,381 Modoc 775 280 1,055 652 Mono 6 Monterey 27,700 27,500 55,200 27,996 Napa 43,060 21,148 64,208 16,953 Nevada 115 115 193 Orange 60,000 60,000 129,352 4 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Number of Bearing and Non-bearing Apricot Trees by Counties — (Continued) County 1920 1920 Trees, 1920 Trees, 1909 Bearing, Non-bearing, Total No. Total No. Placer 8,200 12,110 20,310 4,09'2 Plumas 18 Riverside 455,500 412,500 868,000 83,069 Sacramento 30,000 2,500 32,500 10,480 San Benito 200,750 150,625 351,375 61,694 San Bernardino 119,000 75,100 194,100 111,125 San Diego 11,280 2,150 13,430 20,858 San Francisco San Joaquin 70,748 26,974 97,722 57,007 San Luis Obispo 50,000 38,900 88,900 20,123 San Mateo 9,000 9,000 3,694 Santa Barbara 11,050 31,050 15,512 Santa Clara 627,500 44,400 671,900 783,585 Santa Cruz 73,220 19,807 93,027 63,021 Shasta 1,000 1,000 839 Sierra Siskiyou 366 Solano 246,100 246,100 310,262 Sonoma 31,650 31,740 63,390 9,087 Stanislaus 48,900 34,800 83,700 20,451 Sutter 1,239 44 1,283 5,986 Tehama 38,000 38,000 30,446 Trinity 170 320 490 41 Tulare 21,000 21,000 48,834 Tuolumne 250 127 377 162 Ventura 417,814 243,118 660,932 219,836 Yolo 121,200 121,200 117,228 Yuba 140 50 190 1,481 From the above table it is learned that Riverside County has the greatest total number of trees, 868,000, but Santa Clara has the greatest number in bearing, 627,500. Santa Clara County ranks second in total number of trees and Ventura third. Ventura also holds third place for the number of trees in bearing. By far the greatest increase in any one county in eleven years has been in Riverside County, which moved from eleventh place in 1909 to first place in 1920. While apricots grow best in the deep, moist valley soils, they are found in abundance along the foothills of all our mountain ranges where there is sufficient moisture to support growth. Although the apricot seems to do best in gravelly or sandy soils, it does well where there is a high percentage of clay, and even in stiff adobe. The apricot, on its own roots at least, will not tolerate a waterlogged soil, but on myrobalan root it is adapted to places where the prune might do well, but where the peach or cherry would not survive. Circular 238] TH e apricot in California 5 With the exception of the almond and some Japanese plums, the apricot is our earliest blooming deciduous fruit tree. It is therefore restricted to districts comparatively free from spring frosts. Observa- tion has shown that because of the tenderness of the flower buds this fruit is rarely profitable much above the 1200-foot level, although the tree itself is hardy up to elevations of 4000 feet. One feature of the apricot's popularity has been its habit of early bearing. Properly pruned, it will produce, during the third year in the orchard, from 1500 to 2000 pounds per acre, green weight, the fourth year from two to three tons, and the fifth year between five and six tons. It is true, such yields are much above the average, but they are by no means impossible of attainment. The apricot is not looked upon as a long-lived tree, although it usually outlives the peach, Japanese plum, and generally the cherry. There are, however, many small vigorous orchards of apricots in the state that are forty to fifty years old. The prune and European type of plum will scarcely live longer. The almond, apple and pear, in the order named, will perhaps outlive the apricot, prune and cherry. In congenial soil, the pear will head the list for longevity. Under neglect, the wood of the apricot soon becomes brittle and breaks easily, and organisms of decay admitted through wounds soon wreck the trees. An apricot orchard that is irrigated twice each year after coming into bearing should produce satisfactorily for forty to fifty years, while one that is not properly provided with soil moisture can scarcely be expected to remain profitable longer than twenty-five to thirty-five years. PLANTING THE OECHARD Apricot trees are usually planted 24 feet apart, in squares, but the tendency is to give them more room. On deep soil, especially if irrigated regularly, a distance of 25 feet or even 26 feet each way is better. With the so-called "long" system of pruning coming into general use, trees will need more room than ever before. Under this system they do not grow very tall, but have a much greater spread than under the old plan of annual heading back of all new growth. A very good arrangement would be to set the trees 24 feet in one direction and 26 feet in the other. This would give better room in the direction in which the principal orchard hauling has to be done. When planted 24 x 24 feet, there are 75 trees to the acre, and 70 trees when set either 25 x 25 or 24 x 26 feet. On deep, moist soils, Moorparks and perhaps Royals should be set 26 to 30 feet each way. 6 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION It does not pay to crowd the trees. A grower in the Santa Clara Valley cut out every alternate row in his apricot orchard, with the inten- tion of replanting with another variety. After delaying the replanting for three years, he discovered that with the forty-five trees per acre remaining, the orchard was producing the same tonnage as when there were ninety trees per acre. He claims to have reduced his orchard expenses fully 75 per cent, and sums up by saying, "Why should I prune, spray and cultivate two trees when one will give me the same income ? " Of course, these trees were much too thickly planted in the first place, which accounts for the marked increase in yield per tree when thinned out. In laying out an orchard for planting, it is a good plan to make use of a surveyor's transit in establishing the main guide stakes on two sides of the field. It is a great satisfaction to have straight rows. Also, cultivation is greatly facilitated if there are no trees out of line. A stake should be set where each tree is to be planted. These stakes may be set by the aid of a long wire or surveyors chain stretched across the field and having markers corresponding to the width of the rows, or by " sighting " across the field in two directions. The latter method requires three men, two to do the "sighting," one in each direction, and one to set the stakes. A steel tape line, preferably 100 feet long, is a very important piece of equipment in laying out an orchard. The holes should be dug just deep enough and wide enough to contain the roots without crowding, after they have been properly trimmed. The actual size of the holes will be determined by the size of the average root system of the trees to be planted. As a rule, the ordinary one-year-old tree, 4 to 5 feet high, will require a hole about 14 inches in diameter. Large holes, except in the case of replants among old trees, are unnecessary, provided the land has been properly prepared in advance by deep plowing and harrowing. Before starting to dig the holes, a planting board may be used by setting two guide stakes, which serve to locate each tree at the exact place where it should be set. A convenient planting board may be made from a piece of plank, four feet long, four or five inches wide, and an inch thick. Saw a notch two inches deep exactly in the center at each end and a similar notch on one edge exactly in the middle of the board. Place a conspicuous mark on one side of the board, and always keep that side up when in use. Place the board on the ground with the tree stake in the middle notch. Then drive a small stake in each of the end notches. Remove the board, pull up the tree stake and dig the hole. Two men and a boy constitute a planting crew. The Circular 238] THE APRICOT IN CALIFORNIA boy distributes the trees to the planters as needed. Only a small bundle should be carried at a time, and these kept carefully covered with wet burlap until all are dropped in the holes. In planting, one man uses the shovel and the other does most of the actual planting. With the board in place, the tree is held in the center notch in an upright position. Care must be exercised to see that it is planted at exactly the right depth. Plant as nearly as possible at the same depth as it Fig. 1. — Trees for planting should have the small fibrous roots removed and the main roots shortened to about six inches. stood in the nursery. In heavy soils deep planting may kill the trees or cause them to make a very poor growth. Probably more young trees are destroyed by deep planting than by all other causes combined. Such trees may struggle along for two or three years before actually dying, and in a few instances they may recover if they are able to form a new root system above the old one. Before placing the tree in the hole, the roots should be shortened to a length of about six inches on all sides (fig. 1). All fibrous roots less than an eighth or a quarter of an inch in diameter may be removed entirely. As trees are ordinarily handled between the nursery and the 8 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION orchard, these fine roots make it difficult to pack the soil in contact with the main roots. A knife is much more convenient than shears for trimming the roots. All broken or badly mangled roots should be cut back to firm wood. There is a tradition in some quarters that the "bud" or place where the seedling was cut off should be buried. If this were always done, many high-budded trees would be planted too deep. Others say the "bud," if left above ground, should always be set toward the pre- vailing wind to prevent breaking off. This practice is also unnecessary, as the point of union between bud and stock on a year-old tree is strong enough to stand up against any wind pressure to which it is likely to be subjected. If the union is weak on account of an uncon- genial root stock, the tree would soon break off anyway. The main thing is to see that the top of the tree above the board stands in a perpendicular position and lines up with the other trees in the row. Sometimes the hole will be noticed at a glance to be either too deep or too shallow. It is the business of the man with the shovel to quickly remedy either defect. The first few shovels of earth should be fine, and the planter, especially if he is a beginner, should get down on his knees and, holding the tree firmly in place with one hand, distribute the soil over the roots with the other. The roots should be spread out in all directions and more soil spread over them. When the first few roots are covered, the soil may be firmed with the foot. Ram the soil in tight — under the roots as well as over them, so that all air spaces in the crotches are well filled. When the tree is firmly anchored, remove the board and continue to tramp the earth with both feet until the hole is nearly filled. Both the heel and toe are used in ramming the soil firmly around the roots and into the crotches. If the soil is in good condition for planting, there is no danger of packing too much. Just before finishing, if the tree is noticed to be slightly out of line, it may be straightened by ramming with the heel on one side. A tree may be easily crowded over an inch or two in this way. Do not tramp the last inch of soil, as it is always well to leave a fine surface mulch about each tree. When the planting job is completed, the ground about the tree should be level. If the soil is rather dry, it is well to leave a basin a foot in diameter for the purpose of pouring in two or three gallons of water. A properly planted tree cannot be pulled out of the ground with one hand by a man of ordinary strength. It is advisable to plant apricot trees in California as early in the winter as the soil has been well moistened by rains. Usually the Circular 238] the apricot in California 9 nursery stock cannot be dug until after the late fall rains come. Plant- ing should preferably be done in the month of January. At this time the leaves have all dropped off naturally, and the wood is firm and well matured. It is well to order nursery stock early in the fall or even in late summer, stipulating the grade desired and that delivery shall be made as early in January as possible. Nurserymen usually grade trees according to height, although diameter measurement an inch or two above the bud would be a better way. Commonly trees are graded into three sizes, 2 to 3 feet, 3 to 4 feet, and 5 to 6 feet, but when there is a shortage of stock, a 1 to 2 foot size is often quoted. Sometimes tall- growing trees like prunes, pears and walnuts are offered in 6 to 8 foot sizes. Other things being equal, a medium-sized apricot tree is to be preferred, say 4 to 5 feet, or calipering one-half inch to five-eighths inch. Eastern and northern nurseries are apt to sell by caliper meas- urement, while western nurseries almost universally quote by height. A well-grown, stocky apricot tree three feet high should be very satis- factory, but if trees have been crowded in the nursery row, the four- foot size is better. There is usually a difference of about ten dollars per hundred between the 3 to 4, 4 to 5. and 5 to 6 foot sizes. When trees are received from the nursery, they should always be unpacked at once and heeled-in where the soil is moist. The heeling-in process consists of laying the roots in a trench, leaning the trees at an angle of 45 degrees, with tops pointing toward the south, and covering with earth a foot or eighteen inches deeper than they are to be planted. This deep covering will not injure them while dormant. The trees should be well spread out so that the moist soil can come in contact with all the roots. Nurseries always pack the trees so they will carry safely for the distance they have to be shipped. They should not be permitted to dry out after being received. It is a good plan to heel-in the trees in the orchard so that they will not have to be moved until planting time, and then only as needed. The roots of trees should never be exposed to the air more than a minute or two, especially if the sun is shining or the wind blowing. The ideal time to plant is on a cloudy day when the air is moist. After removing the trees from the heeling-in trench, protect the roots at all times by covering with wet burlap. The importance of protecting the roots before planting and of doing the planting in a thorough manner cannot be over-emphasized. If these precautions are observed, there is no reason why 99 per cent of the trees should not live. 10 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Trees should never be planted until the land has been thoroughly prepared by deep plowing and harrowing until the surface is fine and all lumps broken up. Preferably the plowing should have been done a w r eek or two previous to planting so that the soil may have time to settle. If there are intervening rains, the surface may be fined again by disking or harrowing. While apricot trees have been successfully planted in California as late as early April, the trees by that time are beginning to leaf out and there is considerable risk of getting a poor stand and a puny growth. Where possible, the trees should receive at least one good rain after planting. A soaking rain has often corrected a bad job of planting by settling the soil about the roots before they had time to dry out. Before newly planted trees begin to grow, the tops should be cut off about thirty inches from the ground. If there are any good branches where they are wanted, they may be left after shortening to a length or six or eight inches. Three such branches spaced four to six inches apart may be left and all others cut off. As early as possible after planting, the trees should be whitewashed from top to bottom as a protection against sunburn. Much of the injury attributed to sunburn in summer undoubtedly occurs in winter. A white surface reflects the sunlight, while a dark surface absorbs the heat rays. A whitewashed tree may be 20 to 30 degrees cooler on a sunny day than one that is not whitewashed. After sunset it requires only a few minutes for the bark to cool down to the temperature of the air. Likewise in the morning just after sunrise there may be a quick rise in the temperature from around the freezing point to perhaps 60, 80 or even 90 degrees, according to how much purple coloring matter there is in the bark, or whether the trees are whitewashed. It is the sudden changes or great extremes in temperature after the roots have become active that cause bark injury. Boot Stocks for Apricots. — Apricots are chiefly budded upon seed- ling apricot stock, although peach and myrobalan are also used. A survey of California nurseries in 1919 showed that almost half the apricots propagated that year (49.1 per cent) were on apricot roots, while 27.2 per cent were on peach and 23.7 per cent on myrobalan. The apricot often does not form a good union with the almond, so at the present time that stock is not much used. Seedling apricot is perhaps the best all-round stock. Peach root stock is supposed to thrive better than the apricot in dry or gravelly soils, while myrobalan is used to adapt the trees to locations where it is too wet for either the Circular 238] TH e apricot in California 11 apricot or the peach. While nurserymen ostensibly propagate what the public desires, they often follow their own personal preferences or convenience in the stocks they use. Most orchardists prefer to buy their apricot trees from a nursery. However, they are easily grown at home. Apricot and peach seeds are usually procured from a cannery or a drying establishment. Myrobalan seed or seedlings are generally obtainable from some large nursery or from an importer. In the prune regions, where the trees are largely grown on myrobalan stock, there can always be found scattering trees that have died and been allowed to strout from the roots. The fruit from these wild myrobalans, or cherry plums as they are generally called, should be allowed to ripen on the trees, after which it is collected and kept in tubs, boxes, or even in piles on the ground, where it is allowed to rot, when the seeds may easily be washed from the pulp. These are dried in the shade and placed in bags or boxes of sand and buried twelve to eighteen inches deep until fall. Any kind of seed, apricot, peach, or myrobalan, should be stratified in shallow boxes of sand in October or November. Boxes about four inches deep are best. Place a layer of sand an inch deep in the bottom, then a layer of seed, another layer of sand, and so on until the box is filled. Quarter-inch cracks in the bottom of the boxes will afford the necessary drainage. Set the boxes flat on the ground out of doors in a shady place, and leave them there until planting time in late January or early February. On a large scale, the seeds are generally stratified in shallow pits in the ground. When the seeds begin to sprout they are ready to plant. Plow the land deep at the first opportunity in winter. At planting time the soil should be made fine, and shallow furrows laid off four feet apart. The seeds are planted three to four inches apart and covered two or three inches deep. One pound of apricot seed should produce 300 to 400 trees, peach about 200, and myrobalan, if the seed is all viable, 500 to 600 or more. Some myrobalan trees produce seed that gives 95 to 96 per cent germination, while that of others will scarcely sprout at all. The seedlings should be cultivated and irrigated like a garden, and about July or August they will be ready to bud. Budding may be done as late as the last of September. Trees may be budded when they have attained four- or five-sixteenths of an inch in diameter. Set the buds as near the ground as possible. The buds are sliced from the twig of the desired variety and inserted beneath the bark of the seedling, then tied firmly with a cotton string such as storekeepers use. 12 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION A vertical cut an inch and a half long is made on the seedling, then a horizontal cut halfway around the little tree at the top of the vertical slit, so that the bark can be raised with the point of the knife and the bud pushed downward into place. In cutting the buds, it is immaterial whether the bark containing the bud is peeled off or sliced off with a bit of wood left adhering. Either method gives good results. The following spring the seedlings are cut off just above the buds. If heavy summer winds are prevalent, the trees that grow from the buds may have to be tied to a stake to prevent their breaking off. The suckers below the bud will have to be rubbed off about twice, in order to force the inserted buds to grow. After growing through the season, the trees are ready for transplanting to the orchard. It will thus be seen that one-year-old trees have a two-year-old root system. Sometimes nursery trees make a poor growth the first year from the bud. Such trees are generally cut back to the ground or to a single bud and allowed to grow another year, when they are still sold as one-year-olds. In counting the age of trees in the orchard, it is customary to disregard the time they spent in the nursery. In practice, a five-year- old orchard, for example, is a collection of trees that have spent five growing seasons in the orchard, although the root system may have been two or three years old when planted. PKUNING Pruning properly begins with the training of the young trees the first year in the orchard. After planting, trees are generally trimmed to a straight whip and cut off from twenty- four to thirty inches high. In rare cases, nursery branches in good condition may occur at places where they are wanted (fig. 2) . If so, they may be left after shortening back to six or eight inches (fig. 3). Ordinarily, all the nursery branches are trimmed off, so that a new branch system must be grown from the dormant buds or from adventitious buds which arise from around the wounds where limbs have been cut off. About April it will be found that many buds on the trunk are starting to grow, if the trees have not been injured by becoming too dry before being planted. If left alone, the shoots from the lower buds probably will become not more than an inch or two long, while those from the three or four upper- most buds will grow very rapidly and continue to elongate until mid- summer or later. Where the entire branch system comes from the three or four topmost buds, the branches will be crowded, forming faulty crotches and a very undesirable type of head for the tree. Circular 238] THE APRICOT IN CALIFORNIA 13 The most desirable type of head is one where the branches are spaced as far apart as possible along the trunk. The ideal plan would be to have three branches, spaced six inches apart and arranged Fig. 2. — Apricot tree with lateral branches, planted as received from the nursery. For pruning see Fig. 3. spirally around the trunk. In other words, we may imagine the trunk as being the hub of a wheel, the three branches representing the spokes. This will describe the tree with its three primary branches as seen when looking at it from above. The only way to cause strong branches to grow where they are wanted is to pinch the tips from the undesirable 14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION young sprouts when they are an inch or two long, leaving untouched the three that are located where desired. We usually leave the topmost sprout, another about six inches below it, and a third six inches below that. It is not always possible to find three sprouts just where they are wanted. It is much better to merely tip the undesirable sprouts than to remove them entirely. Each of these short spurs will produce a cluster of leaves which are very valuable, as they not only shade the trunk and help to prevent sunburn, but they help to manufacture food for building up the roots and other parts of the tree. It is a good plan to examine the trees again in June to see if any additional pinching back of undesirable branches is necessary. Much can be done toward shaping young trees in early summer, w T here one side is lengthening faster than another by pinching off the tip of an occasional branch to repress the growth. Pruning One-Y ear-Old Trees. — The first winter pruning of apricots may be done in January, approximately one year after the trees were planted. At this time, three scaffold branches are selected to form the framework of the tree. If the summer pinching of the previous year has been a success, there will be little to do, except perhaps to remove a few superfluous branches and to cut back the three scaffolds pre- viously selected to a length of from fourteen to twenty-four inches, according to the amount of growth that has been made. The longer the branches are left, the more rapid will be the growth of the trees the first year or two. However, the apricot, especially in the coastal region, is inclined to make a very spreading growth, and if the scaffold branches are left too long the first year they may have to be tied up to keep them from drooping over and sweeping the ground. It is usually best, where the apricot trees have made a growth of two or three feet the first season to cut the branches so that the parts left will have about the following lengths: the bottom one 30 inches, the one next to it 24 inches, and the top one 18 inches. If the trees have made less growth the first season, the length of the branches after heading back will be proportionately shorter. In cutting the tops from the scaffold branches, it should be remem- bered that the two uppermost buds left are expected to form the branches that are to complete the framework of the tree. It is important to see that these two buds point in the directions it is desired to have the branches grow. The only object in heading back a young tree is to secure additional branches where they may be needed. Theoretically, the three branches that have been headed back should yield six branches. However, buds do not always grow exactly as Circular 238] THE APRICOT IN CALIFORNIA 15 planned. It is usually possible to secure five satisfactory branches from the six chances, and fortunately five are enough to form a very desirable system of main branches on any tree, whether it be apricot or some other deciduous species. With proper soil and moisture conditions, apricot trees usually make a vigorous growth during their second season in the orchard. The three scaffold branches left from the first dormant pruning will grow not only from the two or three topmost buds of each, but many Fig. 3. — Lateral branches, if well spaced, are left, but are shortened to six or eight inches when the tree is planted. See Fig. 2. of the side buds will grow into spurs, and occasionally one will form a branch. In addition, vigorous shoots may arise from around the points where small branches have been cut out. Any little spurs that may have been left on the trunk will very probably elongate a few inches. Sometimes only a comparatively few of the side buds on the scaffold branches grow at all the first year. Those that remain dormant during the first season may begin to push the second or even the third year, but little can be expected of those that fail to start the first or second season. The first fruit the trees produce may be expected to come largely from the spurs that grow from the side buds on the scaffold branches. Some will come from the spurs which were left on the trunk the pre- vious year or which may arise from dormant or adventitious buds 16 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION during the second season's growth in the orchard. It is during the second season that the buds are formed which produce the first crop of fruit during the third season of growth. During the second season in the orchard, if growth is vigorous, many sprouts from around the pruning wounds, or even from dormant buds', may be produced where they are not wanted. It is a good plan to go through the orchard about the first of May or whenever the sprouts are eight or ten inches long and pull off those that are not wanted, and perhaps pinch the tips from others that are placed where they will make desirable fruit spurs. The pinching is to check the length growth and cause the side buds to be pushed out. At the same time, some assistance may be rendered to the main outgrowths from near the tips of the scaffold branches by pinching back those that are clearly out of line, or where growth is uneven or unsymmetrical. Sometimes one or two branches are inclined to outgrow all the others, which tendency, if not corrected very early, may result in a very unshapely tree and greatly increase the pruning difficulties the follow- ing winter. Pruning during the Second Season. — "When the leaves have fallen after the second season 's growth in the orchard, the trees are ready for their second dormant pruning. It is not advisable to prune an apricot of any age before the leaves have fallen. The leaves of any deciduous tree perform a valuable function, and they are useful to the tree, even in late summer and early fall, so long as they remain green and are firmly attached to the twigs. The pruning of two-year-old apricot trees that have made a satis- factory growth is a comparatively simple matter if the pinching the previous summer was properly done. It should be remembered at this time that five good main branches, properly distributed, are sufficient to form the framework of the tree. Sometimes the trees have a sufficient branch spread and the branches are so arranged that it is advisable to leave six instead of five. This is perhaps more apt to be true of apricots than of most other species of deciduous fruits, because of the spreading habit of the trees. Along the coast and in the coastal valleys there is some danger that two-year-old apricot trees may assume an extremely spreading habit, and thus cause the main branches to be so low as to interfere with cultivation. Fortunately, the apricot takes kindly to having this condition rectified by passing a cord around the tree outside the branches and drawing it just tight enough to hold them all in place. This is easily done if all the branches are of approxi- mately the same size and if the growth has been symmetrical. Other- wise, it may be necessary to tie the branches that are out of place to a Circular 238] THE APRICOT IN CALIFORNIA 17 stake driven by the side of the tree for the purpose. The apricot is different from all other deciduous trees in that the branches do not lean away from the prevailing wind, but, on the contrary, are inclined to grow toward the wind. m \ i? 4/. km./ m Fig. 4. — Two-year-old apricot trees often grow very rapidly, and severe thinning is necessary. See Fig. 5. In pruning two-year-old trees, it will rarely be necessary to cut off any of the tips of the main branches (fig. 4). Considerable thinning may have to be done by removing unnecessary branches (fig. 5) . Each branch on a well-grown two-year-old tree may be expected to show one 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION and often two clusters of small twigs from four to twelve inches long. These clusters of twigs are called fruiting whorls. Where the new growth is only two or three feet long, it is rarely necessary to cut off the tips. However, it is usually desirable to thin the fruiting whorls by removing about half the twigs with the pruning shears. If the total new growth is four or five feet long or longer, and there is a long whip even beyond the first or second fruiting whorl which has curved, under its own weight, and points toward the ground, the branch may be headed back to the last fruiting whorl. However, it is well to first tie up such branches before cutting off the tips to see if the cutting may not be avoided. Fortunately, a tree seems to secure practically all of the benefits of long pruning, even where branches are headed back, if the cuts are made outside the fruiting whorl. Still it should be remembered that every bud left toward the tip of a branch is valuable for making early maturing leaves the next season. Also, the more leaves there are on a tree, provided all are exposed to the light, the more rapid will be the growth of the tree, especially as measured by diameter of trunk and main branches. Hence the necessity for carefully thinning out twigs and even branches where the leaves are likely to be crowded. The pruning during the first and second seasons is for the purpose of giving proper shape to the trees, but the third year we begin to have some regard for fruit production. Some pinching and suckering may be desirable during the third summer. At this time well-grown trees should set a considerable amount of fruit, Indeed it would not be detrimental in any way if the trees should ripen from ten to twenty pounds of fruit each during their third season in the orchard. Most of the fruit will be produced on the spurs two or three feet from the ground. Buds on the fruiting whorls of the main branches and even the side buds farther out may bloom and even set fruit, but only along the coast is this fruit likely to stay on and ripen. Where the fruit does stay on far out on the main branches at this time, it may be necessary to thin it severely, or even to remove it entirely if the branches seem to be unduly weighted down or thrown out of place by heavy winds. At this time, the shape of the tree is a far more important matter than the production of a few extra pounds of fruit. In the interior valley sections', there is not likely to be much difficulty from the production of fruit toward the tips of the new branches on trees of any age, but along the coast this is a real problem, even with old trees, especially where the pruning system has been changed from the short to the long method and consequently the new branches may be very long. Circular 238] THE APRICOT IN CALIFORNIA 19 In addition to the five main branches that are left at the second winter priming, there are apt to be several switches from one to two feet long aronnd the outside of the trees. These are regarded as Fig. 5. — Thinning out superfluous branches admits sunlight to the center of the tree and promotes growth of fruit spurs. See Fig. 4. temporary fruiting branches, and are not cut off where they are not crowding each other. It is, however, advisable to shorten them by removing six to ten inches from the tips to prevent them from making too much diameter growth. Since their position on the outside of the 20 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION trees is such that they will not shade any of the spurs, they are left for the benefit of the leaves they will bear, and also to produce from one to three crops of fruit, after which they may be removed if they are getting in the way of cultivation. By keeping them small by cutting off the tips each year, they can be easily removed at any time they are no longer desired. After apricot trees have come into fruiting, the plan of pruning is much the same year by year. No heading back should be practiced as long as the trees are making a reasonable growth and the fruit sizes up well. Scarcity of moisture in the soil during the growing season or in the fall when buds should be forming for the next year's crop may greatly reduce the annual growth, and may prevent the fruit from attaining a marketable size. Canneries now buy fruit according to size, and their tendency is to demand larger sizes. Dried fruit also is graded according to size, and the price differential between the larger and smaller sizes is sufficiently great to make a big difference in the value of the crop. The aim of the primer should be to keep the head of the tree open so that every leaf gets its share of the sunlight. Every main branch and subordinate branch should be clothed with fruiting spurs five to ten inches apart. If there are too many main branches, the spurs, especially on the older wood, gradually die out. It is perfectly normal for an apricot spur to die after three or four years, but if sufficient light is admitted to all parts of the tree, new sprouts which make spurs quickly arise from around the base of the spurs that have died. Often water sprouts arise from the old wood in various parts of the tree which can be converted into fruiting spurs. Pinching these in early summer has a tendency to prevent them from becoming too long, a condition hard to remedy at pruning time in winter. If water sprouts have not been shortened in summer, the procedure at regular pruning time is to leave them uncut unless they are so long as to interfere with other branches if being devoted to production of side limbs or spurs from most of the dormant buds. The following year they may be cut back to one of the side limbs or spurs, with the assurance that they will seldom or never sprout. Pruning during the Third Season and Afterward. — In the main, the pruning of bearing apricots consists in an annual thinning through- out the entire tree so that every twig and leaf is exposed to sunlight during at least some part of the day (fig. 6). If no heading back is practiced, the long branches sway in the wind and the sunlight filters through the trees, but does not shine on any bare spot on the branches Circular 238] THE APRICOT IN CALIFORNIA 21 for more than a few minutes at a time. Such trees will never suffer from sunburn. It will be necessary to remove annually many small branches, but very few larger than an inch in diameter. If there are too many branches, either cut out entirely those which are superfluous, or reduce their length by cutting to a side branch, but do not head them back. Fig. 6. — An abundance of fruit spurs on the main branches are produced by "long pruning." This four-year-old tree is ready for a heavy crop. The temporary fruiting branches will again need attention in the way of cutting off the tips if they are inclined to continue to elongate. The second year they should bear several spurs, and they may be cut off to one of these. New switches suitable for more temporary branches may have to be tipped. Sometimes new branches may arise high up on the outside of the main branches and compete with these for leader- ship. The remedy is to cut them back so that they are six to twelve inches shorter than the leaders, thus converting them into fruiting branches that may be permanent or temporary. 22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Never allow a sucker or normal side branch to grow up undisturbed on the outside of a leader. Owing to their more favorable position, such branches are almost sure to outgrow the leader and to overcome it in about three years. As before stated, the remedy is to cut off the tops of such branches when they are one or, at the latest, two years old. Long pruning of bearing trees tends to make them fruit heavily. Just how many pounds of fruit a given tree can produce can be determined only by the person who has the constant care of that tree throughout the season, and who sees it when the fruit is harvested and observes the quality of the product, especially its size and color, and then observes what effect the yield has upon the vigor of the tree. The effect of over-fruiting is usually shown by the small size of the fruit and a diminution in growth of the tree. Trees five and six years old, even under heavy fruiting, should make a twig growth on the ends of the main branches from twelve to twenty inches long ; mature trees, twelve to fifteen or twenty years of age, should every year make eight to ten inches of twig growth, and even very old trees should make four or five inches annually. However, these figures are only approxi- mate. The experienced grower should be able to judge from the appearance of the trees, and especially from the appearance of the fruit, whether they are being cropped too heavily. The amount of moisture in the first five or six feet of soil during the growing season will be the chief limiting factor in determining the quantity of high-grade fruit the trees can produce. If irrigation is practiced to supplement this initial amount of moisture, the trees may be expected to mature more fruit than where the orchard is entirely dependent upon rainfall. The grower will have to judge the produc- tive limit of the trees by their behavior and prune accordingly, for he has it within his power to leave them with either a large or a small bearing surface. It should be remembered, however, that long pruning applies both to trees without irrigation and with it. Long pruning should under any circumstances increase the yield from 15 to 20 per cent over what would ordinarily be secured under the old method of annual heading back, but the greatest increase is possible only where there are facilities for summer and early fall irrigation. If the heavy heading back of young trees is a devitalizing process, and this point has been amply demonstrated, it is only reasonable to conclude that old trees would be similarly affected. Under the long- pruning method, the valuable buds at the ends of the twigs are pre- served and the trees are thereby invigorated and enabled to produce more fruit, and yet come through the season in as good condition or Circular 238] THE APRICOT IN CALIFORNIA 23 better than if they had produced less under the old system of heavy annual heading back of most of the new growth. The question is often raised as to whether it will ever be necessary to cut back trees under the long-pruning system. The time may come, especially where the pruning system has been changed from the short to the long on bearing trees, when it may be advisable to reduce the tops by cutting back to lateral branches for the purpose of renewing the wood growth. Trees may have been allowed to overbear through leaving too many branches, or the soil moisture may have been in- adequate and the growth reduced to a dangerous degree. Under such circumstances, removal of a portion of the tops, coupled with a severe thinning of the smaller branches, w r ill result in a rejuvenation of the trees throughout by causing many new sprouts to grow on all the remaining branches. Changing the Pruning System. — The question is frequently asked how to change the system of pruning on trees from ten to twenty years of age or older, from the old or heavy heading-back method to the so-called long-pruning system advocated by the University of California, provided such a change is advisable. Answering the last part of the question first, it may be said that apricot trees of any age are better off not to have the new growth headed back year after year. It is true, however, that the benefits of long pruning on very old trees that are making but little growth may not be noticeable the first year or two after the change is made. But if they are capable of being revived, long pruning will be the best treatment to give them. Unless the trees have been grown with more than ordinarily open heads, the first step to be taken in changing the pruning system from the old to the new is to give them a severe thinning (fig. 7). It may be necessary to remove from two or three to a half-dozen old branches two or three inches in diameter. But the heads must be opened out at all hazards since, if too many branches were left, the main objects to be attained by long pruning would be defeated. Here is where the first mistake has been to leave too many of the one-year-old sprouts on the stumps where the heavy heading was done the previous year. But how many branches and sprouts should be left ? Of course, the main framework of the trees has already been fixed and must be accepted. At a height of four and a half feet from the ground there should be five or six upright branches. Two feet higher up, there should be perhaps eight or ten branches, but no more, unless the trees are exceptionally large. An apricot tree with a top diameter of twelve feet may possibly have eighteen to twenty branches at a point nine 24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION or ten feet from the ground. In the extreme top, where the mass of one-year-old shoots are located, rigid thinning should be practiced until the young branches remaining stand eighteen inches to two feet apart at their tops. Often three to five shoots grow from a single stub. Many of these stubs should be removed, and the growth on the rest thinned to one shoot. If the new shoots in the tops are three to four feet long, it is often a question whether they should be topped lightly, that is, above the main fruiting whorl. In general, no topping is necessary in the interior valley sections, as the fruit buds on these parts may bloom and even set fruit, but most of it will be likely to fall off. Along the coast, however, all the fruit may remain and the weight, coupled with the strong prevailing winds, may cause some breakage to the branches. Also the fruit on these one-year-old sprouts is the least valuable of any on the trees, as it often does not size well and is liable to be sun- burned. Instead of topping these branches, some growers prefer to knock the fruit off with a pole tipped with a piece of rubber hose to prevent injury to the bark. One of the first effects of opening out the head of an old tree is a more or less abundant growth of new spurs up and down the bare branches. New sprouts will continue to break out from the old wood for the first three years. The second year after a sprout arises it begins to bear fruit. It is desirable to have these spurs extend down to within a foot or two of the ground if possible, as they will produce some of the best fruit on the trees. It is a mistake to think that trees will continue to grow higher and higher if the tops are not cut off. If the sprouts at the top are three feet long when the pruning system is changed, they will grow about eighteen inches the first year, ten or twelve the second, five or six the third year, and no more than six inches any year thereafter. The first season, the trees will actually be about two feet taller than under the old system of cutting back to ten or twelve inch stubs, but after that period they will droop over under their load of fruit, and the entire branches will tend to lean outward so that the net result is lower than before. Of course, trees that have been short pruned for a considerable time will have been carried high in the air, a foot or so a year, and such trees cannot be lowered very much, but their further upward growth is effectually stopped by not cutting off the tops. Very rarely does a grower remove enough branches from bearing trees the first year, but as time goes on he learns that more thinning is necessary and does not hesitate to remove more and more branches, Circular 238] THE APRICOT IN CALIFORNIA 25 both large and small. As the remaining branches fill up with spurs, the load is transferred from the extreme top of the trees to sturdier parts below, which are able to support it. Thus it is that long-pruned trees bear heavier loads than before, fewer props are needed, and there is less breakage. Wire Braces vs. Props. — Apricot trees that have been long pruned from the beginning may never need propping or bracing, but old trees, Fig. 7. — Old trees are given a severe thinning out when changing from the " short" to the "long" system of pruning. Fruit wood was produced on the main branches in the center of this thirty-year-old tree in two years by following the long system. even when the pruning system has been changed from the short to the long method, may need some support. Where the branch system is not too spreading, that is, the branches are not too horizontal, a system of wire braces is superior to props. Perhaps the best plan yet devised for supporting branches to prevent their breaking under heavy loads of fruit is to attach one end of a wire to a branch and the other to a small iron ring. The position of the ring will be approximately in the center of the head from top to bottom. The wires are attached to the inside of the branches by means of small iron fence staples driven completely into the wood. Both wire and staples should be galvanized so they will not rust. The wire should be about No. 14. 26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Staples are cheaper and fully as satisfactory as screw eyes. A system of wire braces in a mature orchard should not cost over $40 an acre for labor and materials. The wires last indefinitely, and the main- tenance expense is very slight, as they rarely break. CULTIVATION Apricots require no special attention in the way of cultivation. If there is a cover crop in the orchard, the first plowing may. be done at such time as the greatest tonnage of vegetable matter can be turned under. It is not advisable to plow the land at the same depth every year. In general deep plowing should be preferred, that is, from six to ten inches. Plowing at the same depth every year, especially with a moldboard plow, is liable to bring about the condition known as "plow-pan," especially in soils containing a high percentage of clay. Effective work may be done with either moldboard plows or disc plows. If the cover crop is heavy, it may be dragged under by means of a heavy chain attached to the double-trees or drawbar at one end and to the plow beam at the other, and trailing in such a manner as will best hold the vegetation down until caught by the soil as it rolls over. Where no irrigation is practiced, it is important to do the spring plowing early enough to catch one or more good rains. Plowing should certainly not be delayed until the vegetation has exhausted the moisture from the upper soil. "Where irrigation water is available, plowing may be delayed until some time in April or until after the cover crop has begun to mature. In this way the greatest tonnage of dry material can be added to the soil, and the irrigation water will cause it to rot. Where orchard heating is practiced, it may be desirable to plow before the trees bloom, as it is more convenient to handle the orchard heaters on bare land than where there is much vegetation. There is no evidence to show that plowing just before or during blooming time will have any effect on the bloom or the setting of the fruit, and neither is there any available proof that an irrigation at this time will in any way affect the bloom or fruit-set. Before the surface of the plowed soil becomes baked, it may be double-disked and then smoothed with a harrow. In case it seems unduly porous or has many lumps or clods, it may be firmed and smoothed effectively with a corrugated roller. In the absence of a roller, a heavy drag will accomplish practically the same results. If morning-glory or bindweed is abundant, it is well to use a weed cutter. By using the weed cutter once a week throughout the season, Circular 238] the APRICOT IN CALIFORNIA 27 all the morning-glories may be practically eradicated in one season. The best type of weed cutter has sloping blades that run three to four inches below the surface of the soil, so that all weeds are cut off at this depth. To kill the morning-glory, the plants must never be allowed to show above the ground during the season. Green leaves, if allowed to form, quickly manufacture a new supply of starch for feeding the roots. It is thus seen that killing this weed depends upon allowing no leaves to come to the surface and thereby eventually starving the roots. It should be remembered that weeds of any kind in the orchard are detrimental, as they consume considerable quantities of moisture from the soil. The chief objects to be attained by cultivation are the following : (1) by plowing to turn under the cover crop, to stir the soil that has been compacted by the winter rains, and to fit it for irrigation by loosening the surface layers so that levees can be thrown up ; and (2) by disking and harrowing to fine the surface to prevent the loss of moisture by baking and cracking under the heat of the sun, and also to keep down weeds. Recent experiments indicate that losses of soil moisture by direct evaporation from the soil surface are negligible as compared with the amounts taken out by the trees and other vegetation. The feeding roots of apricot trees probably penetrate to depths of from three to six feet, according to the character of the subsoil and the amount of available moisture. Where apricots are most largely grown, the winter rains are usually sufficient to wet to a depth of from four to six feet. If the winter rainfall is known to be insufficient to wet the ground five or six feet deep, it is advisable to irrigate in late fall. With this excep- tion, it is not believed that irrigation water would serve any useful purpose when applied other than during the growing season or while the trees are still covered with green leaves. When the land has been plowed and brought to a good state of tilth, little cultivation will be needed during the remainder of the summer, except to kill weeds and to put the soil in good condition after an irrigation. Continued cultivation after the surface has been put in good condition is probably an unnecessary expense.* COVER CROPS Melilotus indica, variously called bee clover, sweet clover, or bitter clover, is probably the most valuable cover crop for most orchards. To secure a good stand and a satisfactory growth throughout the * An. Rept. Cal. Agric. Expt. Sta., 1920, p. 45. 28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION winter and spring, it is necessary to do the seeding very early, prefer- ably in August or early September. However, this early seeding is possible only where irrigation water is available. If there is no fall irrigation, seeding cannot be done before the autumn rains begin. Where there is no irrigation water, the safest cover crop is barley or rye. Sometimes a satisfactory growth of vetch (Vicia sativa) may be secured by seeding in early November, although there is no assurance of a good stand and a heavy tonnage unless the seeding is done at least a month earlier. The Canada pea will germinate even in late fall and will continue to grow throughout the winter, but the tonnage of green matter is too light to make it a success as an orchard cover crop. In some sections bur clover is the best cover crop that can be used, as it often reseeds the ground and continues to come up year by year, especially in regions of early autumn rainfall or where the orchard is irrigated in September. The following quantities of seed per acre should give good results : Melilotus, 20-25 lbs. ; bur clover, 20 lbs. ; vetch, 50 lbs. ; barley or rye, 50 lbs. IRRIGATION The apricot, like most other deciduous fruits, requires irrigation after the trees come into bearing, and sometimes before. In most of the apricot districts of Northern and Central California, the winter rain- fall is sufficient to carry young trees through the summer without irrigation. However, vigorous growth is a question of soil supply, and if it is found in any district that trees are not growing properly, owing to insufficient moisture, the remedy is to irrigate. There are a few limited sections where, owing to peculiar conditions of soil, rainfall and sea fogs, successful crops are produced without irrigation, but it is highly probable that they too would be benefited by the application of water. In the principal districts of the state, including both the interior and coastal valleys and the foothills, apricot growing is not usually profitable where no irrigation is practiced. While the trees themselves may not die, they do not make a thrifty growth, and are very apt to decline rapidly in vigor after a few crops have been produced. The yields under such conditions are apt to be irregular. Irrigation should begin in March or not later than the first of April if the winter rainfall has not wet the ground to a depth of six feet. If the ground has been wet to that depth no further irrigation will be necessary until May or June. If the soil has been kept moist and the trees in a continuous growing condition, there need be no harmful results in irrigating near ripening time, but canneries sometimes Circular 238] TH E APRICOT IN CALIFORNIA 29 object to taking fruit irrigated so late, in the belief that the quality will be lowered, although there is no evidence to substantiate this belief. In regions where apricots are grown chiefly for canning pur- poses, it is found necessary to irrigate sometimes about the first or the middle of May in the interior valley sections, and between the middle of May and the middle of June along the coast, where the season of ripen- ing is later. An early summer irrigation seems to be necessary to obtain fruit of the size demanded by the canneries, and does not seem in any way to lower the quality. As a rule, the canneries will not take fruit requiring more than twelve or fourteen to make a pound. If the trees are suffering for moisture, an early summer irrigation within two or three weeks of ripening is apt to crack the fruit, but there is no danger of this if they have been kept in good growing condition. Growers of apricots for drying purposes have not given so much attention to the early summer irrigation so necessary for producing fruit of cannery grade, chiefly because water was not always available when wanted. However, the standards for dried fruit are constantly being raised and the larger sizes are now commanding much better prices than the smaller. The tendency is to follow the same programme of irrigation for all apricots whatever the purpose for which they are used. For best results, apricot trees should be irrigated in early Sep- tember. However, they may be irrigated a little earlier or a little later. In no case should fall irrigation be postponed until after the leaves have fallen. The purpose of fall irrigation is to enable the trees to mature a supply of fruit buds for next year's crop. If only a light winter rainfall is to be expected, there is no harm in irrigating at any time during the winter. A cheap supply of water is often procurable at this time, but it should be clearly understood that winter irrigation is merely a substitute for rainfall, and is applied in the winter rather than in the early spring only for convenience or economy. Apricot trees probably cannot form fruit buds later than December for the next season's crop. A favorite method of irrigating is by the so-called basin or check system (fig. 8), with one or more trees to a check or basin.* The levees which form the checks may be made with a disc, with a ridger, or even with a two-horse turning plow. Where large streams of water must be used, which necessitate high levees, they may be built by plowing usually two rounds between the tree rows and throwing up the levees with a V. Experience is required to learn how high the levees should be to contain enough water to wet the ground to the required depth. *For methods of applying water; See Farmers' Bull. No. 882, tl Irrigation of Orchards. ' ' 30 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION By the check method, water is allowed to flow from one check to the next, the levee being cut when the upper check has been filled. By the basin method, a supply ditch is made every third tree row, each basin is filled to the top, and the water allowed to remain, rather than being drawn off to fill the next basin. Only by this method can a definite quantity of water be applied to each tree. It would be possible to improve the usual check method by filling the lowest check in the tier first and working back through the series but this would necessitate working part of the time on muddy ground. The furrow system of irrigation is not much practiced in apricot orchards in the northern portion of the state, but is preferred in the south. The best method to be used in irrigating an orchard is that which will give the most uniform distribution of moisture throughout the soil. This, in turn, is dependent upon the available head of water, the soil type, the topography or slope of the land, and very decidedly upon the care with which the land has been graded for irrigation before the trees were planted. It is impossible to secure an even irrigation on land which has been poorly graded. The furrow method of irrigation is adapted to the use of small heads of water. It must be used if the irrigating stream is very small, since the number of furrows in which the water is running at any time can be reduced according to the size of the stream. Furrows may be used on a wide range of slopes. The furrow method requires less moving of the surface soil, and no special tools are required to prepare the orchard for irrigation. Much less labor is involved in irrigating in furrows than in basins or checks. The main objection to this method is that the water is not distributed uniformly through the soil, and it is almost impossible to wet the entire soil mass. Improvement can be made on the usual practice by shortening the length of the furrows and by the use of a greater number of furrows between the tree rows. The basin method is best adapted to relatively flat slopes and to large heads of water. Sandy soils on flat grades should always be irrigated by this method, for it is the only way by which definite quantities of water can be applied to each tree. The use of furrows on sandy soil usually results in excessive losses, due to deep percolation near the upper ends of the furrows. The basin method insures an even distribution throughout the orchard. Much surface soil, however, must be moved to form the levees, and since the entire surface of the soil is moistened, the loss by evaporation- is greater than with the furrow method, which moistens only a small part of the surface. With this method constant attention is required to turn out the water as each basin is filled and there is a tendency to puddle and bake the soil. Circular 238] THE APRICOT IN CALIFORNIA 31 The contour method of irrigation is adapted to small heads of water and steep grades. Efficient irrigation on the steep foothill lands can be accomplished only by contouring the orchard. The grade or slope of the tree rows depends upon the ease with which the soil erodes. The only way to determine whether the orchard has been wet to the proper depth is to explore the subsoil with a soil auger, a soil tube, or by digging a few holes. It is advisable for the beginner to apply one of these tests until he is certain that he knows how deep a given Fig. 8. The basin method of irrigation is preferred in some sections. This method insures even distribution of water throughout the orchard, and enables the grower to judge how much water each tree has received. quantity of water will penetrate his soil. After the spring and summer irrigations, it is necessary for the soil to be wet to a depth of five or six feet, but following the early fall watering, the soil need not be wet so deep, as the trees will be able to set a good crop of buds and the starting of the cover crop will be assured by water in the upper soil. However, a light fall irrigation is based on the belief that the winter rainfall will be sufficient to wet down to a depth of fully six feet. THINNING Apricots are thinned to secure larger size and to prevent loss from rotting at ripening time. In the interior valleys there is not likely to be much injury to the ripe fruit from brown rot, but it may be 32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION serious in the coastal region. In regions where fruit is grown for the cannery, thinning is now almost universally practiced. Practically the same tonnage can be produced from a thinned tree, with a major portion of the fruit running twelve to the pound, as if the same tree were not thinned, with perhaps less than a quarter of the crop coming within the twelve grade, the remainder running perhaps fifteen to twenty to the pound. The smallest size the canneries have ever accepted is sixteen to the pound. Usually only twelve are accepted. Formerly all grades of dried fruit sold for practically the same price, but now the Prune and Apricot Growers' Association, which controls 75 per cent of the apricot acreage of the state, offers a premium of several cents per pound for the larger sizes. Thinning should be done about the middle of April or earlier, before the pits become hard. In the absence of definite experimental data covering the subject, it may be advised that the fruits be thinned so that they do not touch when ripe. Preferably the fruits on a well- loaded tree should be four or five inches apart. It is permissible to leave two fruits practically opposite each other on a twig if there are no others within four inches. It is not profitable to try to thin doubles, as when one is removed the other is so badly injured it is likely to drop off. Wherever they can be spared, both should be removed. In sections where there is no danger of brown rot attacking the ripe fruit, clusters of three or even four fruits may be left, especially on young trees, where not much would remain if clusters were rigidly thinned according to the rules given above. Along the coast it is never advis- able to leave clusters. Enough moisture from the damp air at night is held between the fruits that touch to permit the brown-rot spores to germinate. At present no sprays are known that can be safely applied to apricot trees in summer as a protection against the brown rot on the ripe fruit. SPRAYING Apricot diseases controlled by spraying in California are shothole fungus and brown rot. Other diseases, such as scab (Cladiosporum carpophilum) and blossom or jacket rot (Slerotinia libertiana), especially the latter, may cause more or less trouble in certain years. These are only partially controlled by spraying. Serious diseases that cannot be controlled by spraying are : oak root fungus, bacterial gummosis, black heart, and crown gall. The physiological trouble known as sour sap may also be included in this list. Circular 238] TH e APRICOT IN CALIFORNIA 33 The principal insects combated by spraying are : brown scale, black scale, and twig borer. Leaf-eating insects like caterpillars may be poisoned with arsenical sprays, but other methods of eradication (such as burning with a torch) are generally employed. Spraying is not effective against borers attacking trunk and roots. Shothole Fungus (Corynemn beijernickii Oudem). — This disease attacks the fruit, leaves, and twigs, and is the same fungus that causes the peach twig blight. In the apricot, the disease is characterized by spotting of the fruit, perforation of the leaves, and killing of the winter buds. The tender growing twigs may be attacked in spring, causing the tips to die back for several inches. The fruiting twigs are not so liable to be affected as the new ones that are only a few weeks old. The diseased fruit does not rot, but the scabby condition of the skin makes it unfit for canning and, if severe, may ruin or lower its value for drying. The leaves may be so badly perforated as to make the tree look as if they had been fired on with a shotgun, hence the name. The fungus becomes active in the fall after one or two good rains have moistened the soil and rendered the air humid. Spraying at this time is most important. During the winter the fungus works in the buds, and they may fail to open in the spring. All the buds on a single twig may be destroyed in this way, often the twig itself killed. On such twigs there is little or no surface indication of the fungus, although upon close examination the spores may be found in abundance among the bud scales. Occasionally there may be a slight gumming noticed on the dormant twigs, especially around the buds. There is a very pronounced gumming of the young growing twigs when attacked in spring. This is especially true of the young twigs that are produced the same spring they are attacked. The presence of gum is often mistaken for the work of brown rot. Shothole fungus is the worst disease of the interior valley sections of the state. It is rarely seen on apricots along the coast, although occasionally it may be severe enough to make spraying necessary. It may be controlled by spraying the trees both in fall and spring with Bordeaux 4-5-50, lime-sulphur 1-10, or dry lime-sulphur 12-50. The fall spraying should be done in November or early December after the rains have commenced, and the spring spraying after the buds, are noticeably swollen. The latter application, if delayed until the blossoms are beginning to open, will also serve as a protection against brown rot, and, if lime-sulphur is used, will in addition kill any twig borers that may be present. 34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Brown Kot (Sclcrotinia cinerea (Bon.) Wor.). — Brown rot is the worst disease of the coastal region, and seems to be on the increase, not only along the coast, but in rather remote coastal valleys and for almost a hundred miles up the Sacramento River. Both fruit and flowers are attacked. The most damage is done by killing the blossoms and quickly spreading and killing the fruiting spurs. Infection appar- ently occurs when the trees are in bloom or slightly before. The diseased twigs are characterized by severe gumming. Masses of gum are always found on the twigs at the point where the disease stopped advancing. The fungus appears to work with great difficulty in wood that is more than a year old. Large masses of gum, showing the presence of the disease, are often noticed on branches three or four years old or older, but upon close examination it is observed that the parasite has gained entrance to the older wood through the medium of a short spur. Infection does not take place through the bark unless an insect wound or abrasion is present. Brown rot may also cause considerable injury by attacking the fruit at or near ripening time. Where the apricots are growing in clusters, they quickly rot, and the whole mass will be found glued together. Masses of fruit may rot when single specimens escape, hence the necessity for thinning so that the individual fruits do not touch. Apricots that have rotted are apt to dry up and hang on the trees. It is these mummies that are chiefly responsible for carrying the disease over winter. Every specimen will be found to be covered with pustules containing thousands of spores. Decayed fruit allowed to remain on the ground becomes as great a menace as the mummies on the trees. All decayed fruit should be buried, and each mummy should be care- fully picked from the tree and either buried or burned. Plowing the mummies under is not a good practice, as they are likely to be brought to the surface again by cultivation. As many of the diseased twigs as possible should be removed from the trees when the latter are pruned during the winter, because these twigs serve as sources of infection in the spring. It may be a practical impossibility to cut out all of the diseased parts, especially where the fungus has gained entrance to the older wood through small spurs. Some prefer to cut out the diseased twigs during the early summer, when they can best be seen by contrast with the living twigs. It is more expensive to cut them out in summer, and it is very doubtful if their removal at this time will have any appreciable effect in protecting the ripe fruit from being attacked. No spray treatment has yet been devised for preventing the disease from attacking the ripe fruit. Circular 238] the apricot in CALIFORNIA 35 Sulphur sprays apparently cannot be used with safety on apricot trees after the fruit has set, on account of injury to the fruit itself, as well as to the leaves. Other standard sprays, when used at fungicidal strength in summer, are also apt to injure the apricot leaves. Spraying in spring to control brown rot gave good results in 1920, especially when lime-sulphur or Bordeaux, used at winter strength, was applied quite near the blooming time. Results of experiments that spring indicated that the nearer the trees were in bloom when the spraying was done, the better would be the protection against the disease. These results were borne out by experiments and experience of growers in 1921. However, apparently on account of peculiar w r eather conditions, the protection from spraying in 1921 was not so good as that of the year before. Still, the spraying was on the whole a profitable investment. There is some indication that the results of spraying are cumulative, that is, that the disease can best be held in check when the same trees are sprayed year after year. There are also reasons, indicated by results obtained in 1921, for believing that a winter spray, applied as late as January, will help, particularly in badly infected orchards, if followed by the spring spray as the trees are coming into bloom. The spray treatment that can be most recommended at the present time is to use either Bordeaux mixture 4-5-50 or lime-sulphur 1-10, or dry lime-sulphur 12-50 at the time a few blossoms are open and the remainder are in full pink stage. Ordinarily it is not safe to wait until full bloom, because of danger of very severe infection if the open blossoms are moistened by fog or spring rains before the application of the spray. Spraying after the blossoms begin to wilt is not only useless but dangerous; it is too late to protect against infection, and sulphur sprays are liable to injure the fruit immediately after it sets or later. Bordeaux sprays, even of summer strength, applied when the blossoms are falling may not injure the fruit, but they may burn the foliage severely. The amount of spray injury of this kind is usually greater when the moisture content of the air is high. Oak Fungus (Armillaria mellea) . — Oak fungus is common on all deciduous fruit trees except figs, pears on French stock, and walnuts on Northern California Black "Walnut stock. The disease will attack apricot trees on any root stock on which they may be grown. The disease can live on either living or dead wood. It spreads from tree to tree by following the roots. In many sections of California, oak fungus has existed along with the wild vegetation, being especially prevalent on the roots of oak trees, hence the name. If any of the 36 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION diseased roots of a tree are left in the ground, the fungus will remain alive until the roots decay. In this way fruit trees, even in fairly old orchards, suddenly contract the disease in a spot where it was not known to exist before. This is especially true of places where oak trees were abundant. Oak roots in an arid region may remain in the soil for twenty or thirty years before decaying. There is reason for believing that where an orchard is irrigated once or twice during the summer the rate of decay will be much more rapid. Oak fungus is characterized by the white color and fanlike designs on the inner bark, and the peculiar mushroom odor of the diseased parts. Where only one root of an apricot tree is affected, and where the disease may have reached the crown of the tree, there is consider- able gumming on the trunk on the affected side. This gum exudation from the healthy bark a foot or so from the ground may be seen even before the branch on that side begins to show distress. In this early stage, it is possible to save the tree by cutting out the diseased part and disinfecting the wound. To be absolutely safe, it is necessary to dig up all the diseased roots, to prevent healthy ones from coming in contact with them. The presence of the fungus is indicated in early winter by masses of toadstools which come up from the base of the tree. These toadstools, or more properly mushrooms, are edible, especially when they first come up. There is little to be gained by destroying these mushrooms, as it is not believed that the disease spreads from the spores, but from the mycelial growth in the roots, or from the rhyzomorphs, which are masses of fungus threads enclosed in a brownish covering, and which are capable of reaching out into the soil for two or three feet. If they come in contact with the root of another tree, they immediately attack it. Usually the roots of healthy trees sooner or later come into contact with diseased roots from an adjoining tree, and thus contract the disease. When a tree is attacked, the disease generally spreads in all directions. Armillaria spots are therefore usually circular in shape, and additional trees around the border of such spots continue to die each year. The only known remedy for oak fungus is to construct barriers around diseased spots so that the roots of healthy trees cannot invade the diseased area. Perhaps the most effective barrier would be a concrete wall four inches thick, extending down as deep as the roots penetrate, which would be from 3% to 6 1 /o feet, according to the character of the soil. The walls should not come so near the surface as to interfere with plowing or cultivation. By practicing heavy irrigation, the dead apricot roots may be caused to decay in four or Circular 238] the apricot IN California 37 five years. Kather than leave the ground bare where two or three or half a dozen trees have died, and where the area has been walled in, apricots may be replanted by first opening out holes eight to ten feet wide and at least three feet deep. All fragments of roots may be spread on the ground. The disease will die after an exposure of a week or two to the summer sun. The holes may be filled with fresh soil, and there is a chance that the old diseased roots may decay before the roots of the replanted trees come in contact with them. There is no assurance, however, that replanted apricots will not contract the disease within a few years. The only safe plan is to replant with pears or walnuts, or to use the land for garden purposes or alfalfa. Bacterial Gummosis (Pseudomonas cerastes Griffin). — This disease is new in California, having been serious on apricots only during the last three or four years. On young or old trees, the disease is mani- fested by copious gumming. The masses of gum may be light amber in color, but as a rule they are of a decidedly yellowish tinge, and the typical color is a pale yellow. The typical gum mass caused by gummosis is quite opaque, while masses of gum produced from other causes are transparent. The final test of gummosis is the pocket or cavity beneath the bark, which is filled with a pus-like material, at least when the disease is active. On old cherry trees the pus pockets sometimes occur between the inner and outer layers of the bark. The "pus" seems to collect in the cavities, and there may be a noticeable swelling of the bark until the latter breaks and allows the contents of the pockets to ooze out. Apparently the mechanical injury to the bark in the vicinity of the pockets may sometimes cause a certain amount of gumming, but this gum will be amber- colored and trans- parent. Gummosis will kill apricot trees from one to three years old, usually the year they are attacked, while old trees may survive for several years. Although the disease is usually confined to the trunk and branches, it may occur even in the one and two-year-old twigs. It is most active during the winter months, but may be active in the spring as late as April or May, especially in the cooler regions along the coast. Gummosis, being a bacterial disease, is readily spread by pruning tools. Pruners should be taught to recognize the disease, and in prun- ing affected trees they should be provided with a supply of bichlorid of mercury for disinfecting their shears or saws after cutting into the diseased parts. The treatment for bacterial gummosis is to cut out all of the diseased parts of the bark, scrape the wood, and then apply a 38 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 1-500 solution of bichloride of mercury or mercury cyanide. After the wound dries, it should be thoroughly painted with Oronite. If taken in time, diseased trees can easily be saved by this cutting-out method. However, young trees are likely to be killed before the disease is noticed. Black Heart (VerticilUum sp.). — This is an obscure disease which causes apricot branches to die, usually in early summer. It is generally worst in trees from three to five years old, although it may occur in much older trees. In May or June the leaves on an affected branch, particularly toward the tip, suddenly collapse, and they may be seen to be wilted at points lower down. On cutting off such branches, it is found either that the entire heart wood is black, or that an outer ring of the heart is darker than the remainder. In many instances, black heart seems to be associated with excessive irrigation, especially during the first year or two the trees are in the orchard. A great deal of black heart has been observed in orchards where strawberries or tomatoes were grown between the tree rows. Both these crops are usually irrigated several times during the season, and the watering is continued almost until the first frost comes. Black heart has also been observed to occur on two or three-year-old trees where no irrigation has been practiced. The disease is caused by a fungus, and infection seems to come from the soil. No satisfactory treatment is known. In the past, growers have been advised to cut back the diseased parts to healthy wood, or even to dig up the trees. While cutting back the trees may not stop the disease or prevent its recurrence, the removal of dead branches can do no harm, and greatly improves the appearance of the trees. Trees have sometimes been observed to make a complete recovery after a year or two. On the other hand, the disease has been known to recur in trees the following year after diseased parts were cut out. On the whole, it is better to cut back to healthy wood and give the trees a chance to recover. Crown Gall (Bacterium tumefaciens) . — This is an old disease that causes characteristic warts or galls on the crown or roots of the trees. It is worse on almond or peach stock than on myrobalan or apricot. The disease rarely kills a tree, but may be one of the factors which reduces the vitality. The crown gall does the most harm after it has encircled the crown. It is apt to be worst when borers are prevalent. The galls make good hiding places for the borers, and the latter undoubtedly spread the infection. If the galls are noticed when small, or considerably before they have encircled the tree, they may be chiseled off and the wounds Circular 238] THE APRIC0T IN CALIFORNIA 39 painted with a concentrated solution of copper sulphate (bluestone). The wounds should then be sealed with Oronite. Sour Sap. — Sour sap does not seem to be caused primarily by a fungus or a bacterium. It is most common in young trees. It most frequently occurs where the roots of the trees are "water-logged" in winter, which may occur if the subsoil is heavy and not well drained. It also occurs in gravelly spots where the soil is subject to extremes of moisture and of temperature. Sour sap is usually most prevalent on the sunny side of the trunk, but in severe cases the entire tree may become involved. This trouble may be recognized by the characteristic odor caused by fermentation of the sap in the affected parts of the tree. Apparently the most direct cause of sour sap is extremes of tem- perature in late winter or early spring. The tissues of the trees may become active on warm, sunny days, thus rendering them susceptible to injury from low temperatures which may follow. Trees grown in soils subject to extremes of moisture and of temperature are liable to make intermittent growth. They are especially liable to make a soft, succulent growth in late fall, just when they should be "ripening" their wood and storing plant food reserves for winter. Such trees have a less definite winter rest. They are more liable to be awakened into activity on sunny days in late winter or spring and more subject to injury from subsequent cold spells. On the other hand, trees are less susceptible to sour sap if they make uninterrupted seasonal growth ; cease length growth in early autumn, ripen their wood and store plant food reserves for winter. Such trees have a more definite winter rest, they are less liable to be forced into activity or growth on sunny winter days and are more resistant to subsequent cold spells. Treatments which oppose sour sap are possible. If there is an impervious layer of hard pan, not far below the surface, it should be broken by subsoiling or by the use of dynamite to afford drainage into the pervious subsoil beneath. If dynamite is used, the work should be done when the subsoil is dry enough to avoid "puddling." On poorly drained soils a furrow may be opened on each side of the tree row in the fall to carry off surface water during heavy, winter rains. Low places in the orchard where winter water stands, should be drained by means of furrows leading to a convenient outlet. Gravelly spots in the orchard should not be allowed to dry out unduly in summer. Such areas may be irrigated more frequently or more abundantly if conditions admit. Moisture may be conserved by tillage and keeping down weeds during summer. Manure applied to dry spots will further conserve soil moisture. Where winter rainfall 40 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION is low, proper contouring about trees on dry spots may catch winter run- off and conserve it in the soil. Sour sap is also opposed by whitewashing young trees during December. The wash should be reapplied, if necessary, to retain a white cover until spring. The whitewash reflects the heat on sunny winter days and prolongs the rest period of the trees. Whitewash on the trunk should extend a few inches below ground, since the growing layer of the tree gets hottest at the surface of the dark soil, where the most heat is absorbed. The coloring matter in the bark of young trees frequently absorbs heat enough on sunny winter days to raise the temperature of the growing layer 25° to 30° F. above the temperature of the air. The whitewash reflects the heat, so the tree remains at atmospheric temperature or even a few degrees lower. In selecting nursery stock to plant on soils where sour sap is likely to occur, it is safest to choose trees that ceased length growth moder- ately early and perfected their growth for winter, rather than trees which grew unduly late in the fall. Death of young trees, due to bacterial gummosis or other causes, is often termed sour sap. Green Rot (Sclerotinia libertiana) . — This is known also as blossom or calyx rot and sometimes jacket rot. The disease attacks the green fruit a week or two after the blossoms fall, when there is much fog or rainy weather. Apparently the spores find lodgment beneath the " jackets, " and the moisture enables them to germinate and grow. Spots appear on the little apricots, and sometimes the blossom-end or one whole side decays. The fruit soon drops. Green rot does not appear some years, but is of considerable economic importance during seasons when weather conditions favor its development. No separate spray treatment has been worked out for this disease. Probably the spray programme used against brown rot will be as effective as any treatment that could be suggested. INSECTS Brown Scale (Lecanium comi Bouche). — This insect is also known as the European Fruit Lecanium. The chief injury to apricots is an indirect one. The insects excrete a honeydew which covers the leaves and fruit, and a sooty mold grows abundantly in this honeydew and gives a blackened appearance to the fruit, causing it to be rejected by the canneries. Such fruit can be saved by drying, but it does not make a fancy product. Circular 238] T HE apricot in CALIFORNIA 41 The brown scale ranges in color from amber to a dark reddish brown. The insects are about one-eighth of an inch long. The eggs are very small, slightly oblong, and pearly white. The young are light yellow, turning a reddish brown as they grow older. The eggs are laid in April and May. Upon hatching, the young settle upon the leaves and younger twigs, where they remain during the summer. During the winter they are in a half-grown stage. Severe infestations occur only periodically. There is but one brood a year. Brown scale is very common throughout the state, but is worst along the coast, especially in the Santa Clara Valley section. It may be controlled by spraying the dormant trees with crude oil emulsion, distillate emulsion, or a miscible oil. Preferrably, spraying should be done during January and February.* One thorough spraying every two or three years should be sufficient. Black Scale (Saissetia oleae). — The occurrence and habits of the black scale are very similar to those of the brown apricot scale, and the same remedial measures will apply, especially the use of miscible oils and distillate emulsions. Twig Borer (Anarsia lineatella Zeller). — This insect is generally known as the peach twig borer, as it was first observed to occur in peach trees and has only lately spread to apricots. The insects attack both the young growing twigs and the fruit. The larvae or worms winter over in small chambers made just beneath the bark in the crotches, being found most commonly where branches are from one and a half to two inches in diameter. They may be located by the small chimneys of frass pushed out in the process of making the burrows. As the leaf buds begin to open in spring, the insects crawl out and begin to feed. They start in the leaf axils near the tips of the twigs and bore down the center of the stem, thus killing the tips. By May they are mostly full-grown. They conceal themselves in crevices in the bark and within one or two weeks emerge as adult moths, steel-gray in color, and about one-half inch from tip to tip when the wings are spread. Not all of the larvae become full-grown by May, and the later maturing individuals of the first brood attack the fruit just as it is beginning to ripen in June or July. The moths immediately begin to lay eggs, and when the young of the second generation have hatched out, instead of attacking the fruit, as is generally supposed, they begin at once to construct their hiding places, where they remain throughout the rest of the summer and over winter. * See Univ. Calif. Circ. 224, "Control of the Brown Apricot Scale on Deciduous Fruit Trees." 42 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The twig borer may do very serious injury to apricot trees one and two years old by destroying the tips of the branches, thus making it impossible to grow shapely trees. The injury may be so severe on either young or old trees as to cause them to be seriously weakened. Fortunately, control measures are simple and unusually effective. The standard treatment is to spray the trees with lime-sulphur 1-10 as the buds begin to show signs of opening in spring. On bearing trees, the treatment may be delayed until the trees are coming into bloom, when the spray will also serve as a treatment against brown rot. In certain sections, the twig borer does much harm by causing the apricots to be wormy. California Peach Borer (Mgeria opalescens) . — This borer usually attacks the trees just beneath the surface of the ground, although they may be found at the surface or even a few inches above. Borers of this kind are found in California only along the coast, where they often becomes a serious pest of all stone fruits. More damage is done where apricots are growing on peach root than on either apricot or myrobalan. Borers should be thoroughly dug out in the fall or winter, and the wounds sealed up with hard asphaltum of the grade known as S-Flotine. This must be applied hot. Roofing paint known as Oronite may be used. The latter is cheap and can be applied cold. It is a good plan to apply a heavy coating of cne of these materials over the entire crown of the trees from six to eight inches below ground (down to the main roots) to four or five inches above ground. The Oronite requires renewal every year, while the asphaltum usually lasts two years. The parent of the borer, a wasp-like moth, lays its eggs on the lower part of the trunks of the trees from April to June, and these hatch in from fifteen to thirty days. The borers, when very small, seek shelter in the crevices of the bark and begin at once to bore their way into the wood. During the summer they work upon the growing inner bark, burrowing upward or downward at will. The frass, and also gum, is forced out of the exit holes through the side of the trees. The borers remain in the burrows during the winter months, and continue fairly active. In January or February, they transform into pupae. These remain in the old burrows for about one and one-half months, when they emerge as full-grown moths, which shortly begin to lay eggs. There is but one generation a year. The Flat-headed Apple Tree Borer (Chrysobothris femorata). — This insect is apt to attack any young tree that has become weakened Circular 238] TH e apricot in California 43 from any cause, but especially from sunburn. Healthy trees with a full sap flow are very rarely attacked. .The borers work on the trunks, usually six to twelve inches from the ground. They do a great deal of harm in the interior valleys and adjacent foothill sections. Only rarely do they occur along the coast. The parent of the flat-headed borer is an oblong, flattened, and metallic greenish-black or grayish beetle. The females are about one- half inch long. The borers are white or yellow, and from one-half to three-fourths of an inch long. The head end is greatly enlarged and flattened, so that the burrows they make are elliptical in shape. In a few weeks they will completely girdle a young tree. The eggs are laid in early spring under any loose scales of bark or in crevices. After hatching, the borers, which are very small at first, bore into the sapwood upon which they feed. Later they work into the older and firmer wood. Finally they work outward nearly through the bark, form large cells, and go into the pupal stage. In the spring they emerge as full-grown flying beetles, ready to begin egg-laying. Both young and old trees are attacked, the latter often in the branches if they are sunburned. Control measures consist in prevention. Whitewash or shade the trunks of young trees to prevent sunburn, and do not open up large holes in the tops of the trees in pruning. Keep all trees growing steadily and flat-headed borers will pass them by. FEOST FIGHTING On account of its early blooming habit, the apricot is apt to be injured by spring frosts. Experience has shown that an ordinary frost at blossoming time may be successfully combated by heating the air of the orchard. The cost is small compared with the value of the crop. The heating is done by burning stove distillate or crude oil in pots or heaters made for the purpose. The object of using heaters is to add enough heat to the air to prevent the temperature from falling below the critical point. Smoke is of but little value. The so-called "lardpail" or open type of pot or heater is the one in most common use, although some orchardists are installing the improved stack type. The one-gallon open type with flame deflector costs from 30 cents to 35 cents and will burn for approximately two hours. The two-gallon size with deflector costs about 45 cents and burns for approximately four hours. In a few cases, growers have used tin cans, size number 10, with a fair degree of success. 44 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION From seventy-five to one hundred heaters of the open type are required per acre. A smaller number of the stack type are sufficient. When the small heaters are used, one is usually placed in each square formed by four trees (fig. 9). A double row is used on the outside, especially on the windward side. Storage facilities to handle fuel for two or three successive firings should be provided. For small orchards, near an oil supply station, enough oil may be secured from day to day and stored in barrels to last for any ordinary cold period. For orchards of ten acres or more in size a storage tank of 2000 to 5000 gallons, conveniently located, is essential. Tested thermometers are an absolute necessity. It is well to have several, placed in different parts of the orchard at a uniform height from the ground. An automatic electric frost alarm may be placed in the coldest place in the orchard and arranged to ring a bell in the owner's sleeping apart- ment when the temperature reaches the danger point. Tested ther- mometers cost from $2 to $3 each and an electric frost alarm costs about $40 with wire extra. Other equipment needed is a supply of covers for the pots to exclude rain from the oil, a lighting torch, and a tank wagon or handy truck holding several barrels to distribute the oil to the pots'. A handy torch for lighting the pots consists of an oil can with a long spout, such as locomotive engineers use. These torches can be secured from dealers handling the heaters. Heaters are usually lighted when the temperature at the coldest place in the orchard (usually the lowest place) reaches 31° F. The pots are lighted by the flaming drops of gasoline or distillate falling from the spout of the torch. An active man should be able to light from 200 to 300 pots per hour. All of the pots are seldom lighted at once. Usually the double row on the outside and several inside rows on the side of the orchard from which the breeze is blowing are lighted first, followed by alternate pots in the interior of the orchard as quickly as possible. If the temperature is not raised above the danger point in from twenty to thirty minutes the remainder of the pots are started. Much of the procedure covering these points must be learned by actual experience. With the ordinary equipment now in use it is comparatively easy to raise the temperature of the air in an orchard two or three degrees, but very difficult to raise it more than four or five degrees. For- tunately it is rarely necessary to raise the temperature more than two or three degrees in most districts where apricots are grown. Frosts usually occur on clear, comparatively quiet nights. The presence of wind generally causes a mixing of the stratas of air of different tern- Circular 238] THE APRICOT IN CALIFORNIA 45 perature, preventing the settling of cold air in the low places. If frost does occur when there is a perceptible wind, it is much harder to combat than one on a quiet night. The coldest time of the night is Fig. 9. — One orchard heater per tree is usually placed in the square formed by four trees. A double row of heaters is placed next to the outside row on the windward side. usually about daybreak or perhaps just before sunrise, hence the heaters must have sufficient capacity to burn until after sun-up if necessary. It is easier to heat an orchard of old spreading trees than 46 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION one where the trees are small. The top branches in large trees have often been observed to produce fruit when the buds lower down were killed by frost. The grower who is located in a district where orchard heating is necessary should make a careful study of conditions in his orchard as regards air currents, cold places, and average duration of frosts at different stages of development of the blossoms and young fruit. Much needless expense can be saved by the careful man who knows when to heat and when not to heat. In the absence of definite figures covering California conditions the temperatures which apricots are likely to endure for thirty minutes or less without being killed are as follows: Buds closed, but showing color, 27° to 30°; in full bloom, 28° to 31° ; after fruit has set, 30° to 31°. The best complete treatise on orchard heating easily available is Farmers' Bulletin No. 1096, entitled "Frost and the Prevention of Damage by It." HAEVESTING APRICOTS For Canning Purposes. — Canneries now desire all fruit delivered to be ripe, though firm. This means that the apricots must be yellow, but may or may not have a blush on one side. Several pickings may have to be made so that all the fruit will be exactly in the right con- dition. What has been said applies to the Blenheim and Royal. The Tilton may be yellow, at least on one side, and still be too green to be harvested for canning. If in doubt, samples should be submitted to the cannery before heavy picking begins. Tolerance for overripe or soft fruit is very small. If there is more than a mere sprinkling of overripe fruit, the whole load may be rejected. Canneries take but one grade of fruit, all of which must be above a certain size. The size specification varies from year to year, accord- ing to market conditions and the extent of the crop. One season the fruit must run twelve to the pound, while the next fourteens or even sixteens may be acceptable. Undersize fruit is dried or sold to a by-products establishment. The fruit is picked from the trees by hand. Each picker usually carries a 12-quart tin pail which he holds on his arm or hangs on the ladder by a wire hook. The buckets are emptied into 40 or 50-pound lug boxes, which are filled only slightly more than level full to prevent crushing when they are stacked in the field or in hauling. The cannery usually furnishes the lug boxes, but the grower may do all the hauling to and from the cannery or to the cars. Competition among buyers or other special conditions may cause exceptional arrangements to be made. Circular 238] TH E APRICOT IN CALIFORNIA 47 The average production is about four, although exceptional yields as high as eight tons have been reported. For Drying. — For drying purposes it is highly desirable that the fruit be picked from the trees rather than knocked off with poles, as is sometimes done. Bruised fruit does not make a first-class dried product, and is discriminated against under the grading regulations of the Prune and Apricot Growers' Association. The fruit should be riper than that preferred by canneries, but should be firm. Apricot cutters, usually women and girls, slit the fruit around the suture or seam, remove the pit, and lay the halves cup-side up directly on trays. The cutters sit at tables and helpers dump the fruit in front of them. Apricot cutting is nearly always done as piecework, at so much per box. The pits are tossed into a box on the floor and saved, as they have considerable value for planting and for by-products purposes. Assistants remove the trays as filled and stack them on trucks. They are then rolled into the bleaching house and exposed to the fumes of burning sulphur for about three hours. If the fruit is too green, a longer period of sulphuring is advisable. When the fruit is well sulphured the juice collects in the "cup," which makes careful handling of the trays necessary. After sulphuring, the fruit should be a beautiful golden-yellow. Sulphuring shortens the drying period, prevents decomposition, and affords considerable protection from insects while in storage. In sulphuring, two or three pounds of common powdered sulphur are placed in a pit beneath one end of the stack of trays and lighted by touching a match to a handful of excelsior or a small roll of paper. Eight to ten pounds of sulphur is allowed for each green ton of fruit. The sulphur house is usually just large enough to contain a stack of trays four to six feet high. The house itself may be constructed of concrete, brick, or wood. Sulphur houses must be provided with adjustable ventilators at the top. To be effective, the sulphur must burn slowly and the fumes should circulate freely. In lieu of a house, an inexpensive sulphuring device called a hood may be made by constructing a framework of 1 x 4 inch boards and covering with building paper, with numerous laths nailed across all sides for the protection of the paper. On either side, two of the boards should project a foot or so at both ends to serve as handles for lifting the hood over the trays and off again at the end of the bleaching period. Earth may be piled against the side of the hood to prevent undue loss of the fumes. The paper cover at best will contain enough openings to give all needed ventilation. 48 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The trays are exposed to the sun until the fruit is nearly dry. The time for drying varies, but is usually about two days in the sun, fol- lowed by two or three days with the trays stacked in the shade. This slow drying in the shade gives the fruit a better texture. Apricots are dry enough when they are leathery to the touch, not hard nor brittle. Fruit that has become too dry may be processed by dipping in boiling water. It is placed in a wire basket and submerged but a few seconds. when it may safely be stored in bulk while wet. Unless the water is boiling the fruit will mold. Newly dried apricots may be stored in lug boxes or in bulk in bins until delivered to the association's ware- house or to a buyer. Apricots dry at the rate of about one pound for each five pounds of fresh fruit. A good yield would be one and one-quarter tons of dried fruit per acre, although about three-quarters of a ton is nearer the average. For the Fresh-fruit Market. — For shipment as fresh fruit to eastern or other markets, apricots are harvested when they become a light yellow, particularly if there is a blush on one side. The fruit is carefully sized, often wrapped, and packed in 5-pound baskets. Four of these baskets make a crate. The standard basket is approximately 8 inches square at the top, 6% inches long, 16 inches wide, and 4% inches deep, measured inside. When packed in layers in baskets with sloping sides, the state law says, "no layer below the top layer shall contain a greater numerical count than the top layer." "When packed in layers in containers with straight lines, each layer must contain approximately the same number of fruits. The variation in size (except in baskets) "must not be more than one-eighth of an inch when measured through the widest portion of cross section." Generally speaking, apricots when packed shall be mature, but not overripe, well colored for the variety and locality, virtually uniform in quality, practically free from insect and fungus pests, rot, bruises, frost injury, sunburn, and other serious defects, and virtually uniform in size. The chief early apricot districts of the state are in the vicinity of Vacaville, Solano County, especially Vaca Valley and Pleasant Valley, and the nearby Winters and Guinda districts in Yolo County. Another increasingly important early district is the Imperial Valley. Heavy shipments of early apricots formerly went east from the Newcastle section of Placer County, but the plantings there are being rapidly replaced by plnms and peaches. Circular 238] TH e apricot in California 49 The Newcastle is the favorite variety of apricot for early shipment, but the Royal and even the Blenheim are also shipped to a considerable extent, especially from the Imperial Valley. VAEIETIES OF APRICOTS The chief variety of apricot for drying purposes has been the Royal, for canning the Blenheim, and for early shipment to fresh fruit markets the Newcastle Early. In especially early or late locations, other varieties may be shipped fresh. In like manner, all varieties may be dried and others, especially the Royal and Tilton, in addition to the Blenheim, be sold for canning. In 1920 the California State Department of Agriculture called a conference for the purpose of standardizing fruit varieties for plant- ing. Representatives from various interests were present, including growers, nurserymen, canners, shippers, and officers of dried and green fruit associations. An effort was made to eliminate useless varieties by recommending that their further propagation be discontinued. The following apricots were recommended for planting: For the Coast : Blenheim, 100 per cent for canning. Could also be used for drying. For the San Joaquin Valley : Tilton, 100 per cent for drying. Could also be used for canning. For the Sacramento Valley : Tilton, 50 per cent ; Blenheim, 50 per cent; for drying or canning. The Royal was recommended as a commercial variety, but for what purpose or locality was not stated. However, it was understood that it might be replaced by the Blenheim and Tilton, which, it was thought, would answer all purposes heretofore served by the Royal. The planting of Moorpark was recommended for drying purposes only, without mentioning localities. Routier's Peach and Hemskirke were recommended only as home orchard varieties. Royal. — A French variety which for years was the leader in the state in point of acreage planted. The Royal has been our chief drying variety. It is also excellent for canning ; of a large size when properly thinned, dull yellow in color with orange cheeks, free stone, fine flavor, good bearer, fruit ripening evenly when trees are properly opened up by pruning ; fruit roundish, medium to large, oval, slightly compressed and with a shallow suture ; flesh pale orange, firm and juicy, and with a rich flavor when fully ripe. The time of ripening at the University Farm, Davis, in the Sacramento Valley, has been from the 10th to the 50 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 20th of July. In the Imperial Valley it may ripen nearly a month earlier. Blenheim is now first in popularity for all purposes; the leading canning variety in the coastal region ; so nearly like the Royal that growers of wide experience cannot tell the two varieties apart ; a vigorous grower, and on the coast a regular and prolific bearer; reputed to be later in ripening than the Royal, but at Davis the two are ready to harvest at almost the same time. Grown for canning, the fruit must be heavily thinned to secure proper size. Fruit similar in all respects to the Royal. A shy bearer at Davis, but a heavy producer in the San Francisco Bay region and in all the coastal valleys to the southward, and also in Riverside County. Very susceptible to brown rot throughout the coastal region. Tilton is now next in popularity to the Blenheim ; grow T n chiefly in the interior valley sections ; often blooms two weeks later than the Royal or Blenheim, which gives it considerable protection from frost. So far, the Tilton has been almost entirely free from attack by brown rot, because no doubt of its late blooming habit. At Davis, the Tilton ripens fully a week later than the Royal or Blenheim. The trees are strong, healthy growers, and excellent producers. At Davis trees now fourteen years old have increased steadily in yield for the past six years, under the long system of pruning, and so far, the tops have not had to be reduced by cutting to laterals to induce new twig growth. Wickson says the Tilton was originated by J. E. Tilton near Han- ford, Kings County, about 1885 from a chance seedling. The fruit is large, symmetrical, and has a free stone. The flesh has a fine yellow color that makes it acceptable for both drying and canning. The chief drawback to the Tilton is its habit of coloring before it is ripe. If judged by the usual standards, it is apt to be taken to the cannery too green. This is doubtless the reason canners discriminate against it in some quarters. The Tilton is rapidly becoming the favorite for all purposes in the Sacramento and San Joaquin valleys. Moorpark. — This is an old English variety which is excellent for drying. The trees are unusually large and generally very robust in point of vigor. The fruit is larger than the Royal, Blenheim, or Tilton, and of very fine flavor, which makes it a superior variety for eating purposes. However, it ripens too late to find a place in the trade. The Moorpark as a tree appears to thrive wherever apricots can be grown, but seems to do especially well in the cool coastal valleys. It has the reputation of being a shy bearer, but where light pruning with no heading back is practiced, it usually produces well. In sec- Circular 238] the apricot in CALIFORNIA 51 tions where the Blenheim is grown almost exclusively, the canneries will usually not take the Moorpark, for the reason that they do not care to mix varieties. The Moorpark is very profitable for drying when the trees bear regularly. Nearly all the fruit makes a fancy dried product which is readily accepted under the grading rules of the Prune and Apricot Growers' Association. Hemskirke. — A shy bearer in many places, and recommended only for planting in home orchards. The fruit is described as "large, roundish, but considerably compressed or flattened ; skin orange, with red cheeks ; flesh bright orange, tender, rather more juicy and sprightly than Moorpark, with rich, luscious, plum-like flavor; stone not per- forate, rather small, and kernel bitter." The quality for eating pur- poses when fresh makes it a desirable addition to the home fruit tree collection. Newcastle. — "Originated with C. M. Silva & Sons, Newcastle, Placer County, in 1881. Size medium, round, with spherical pit ; free stone; not quite so large as the Royal nor quite so rich in flavor, but more highly colored ; rather darker on the sunny side. Early, regular and good bearer, a medium grower, more upright than the Royal." Ripens three to four weeks earlier than the Royal at Davis, in the Sacramento Valley. This is the chief variety shipped to the early eastern markets. It is grown chiefly in the Coast Range foothills and valleys, particularly in the vicinity of Vacaville. Ripens in the Imperial Valley as early as April or the first part of May. COST OF GROWING APRICOTS The cost of growing apricots cannot be stated definitely. Owing to increased cost of labor and materials during the past few years, the cost has been greater than during the pre-war period. At the present time, prices are being reduced, but whether or not the pre-war level will be reached cannot be predicted. In attempting to arrive at a conservative estimate of costs, the Division of Farm Management at the University of California has compiled considerable data. The costs given represent averages based on pre-war conditions, with such figures on present prices as are available at this time. Value of Land: Raw Land : High (with water) $400.00 per acre Low (with water) 150.00 per acre Usual (with water) 200.00 per acre Developed Orchards: High-producing $1,200.00 per acre Usual producing 800.00 per acre 52 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION In the San Francisco Bay region, including the Santa Clara Valley, all values will range about 50 per cent higher than the figures given above. Cost of Establishing Orchards: (Irrigation system or water right included in price of land). Clearing, grading and leveling land for planting ($10 to $75) $20.00 per acre Trees (at 20c, price in 1920 much higher, 50c up) - 15.00 per acre Setting out ($4 to $8) _ 5.00 per acre Replanting 1.50 per acre These costs are subject to extreme variation, depending upon the topography of the land and the prevailing scale for man and horse or tractor work. Owing to greatly increased demand, the price of nursery trees has been much higher during the past two or three years than formerly. The annual cost from setting out to self-sustaining age is given approximately as follows : Cultivating $6.00 per acre Irrigating ($2 to $12) 6.00 per acre Pruning 3.00 per acre As intercrops are usually grown in young orchards, the expense of cultivating and irrigating is, as a rule, borne by the intercrop. No data are available on the cost of these operations at the present time. The diversity in the actual operation connected with a mature orchard, together with the average grower 's disinclination to keep cost figures, renders it difficult to give a statement of costs that will be suitable for all conditions. The comparatively high cost of many of the necessary orchard operations is due to the high wages that have prevailed during recent years. At the present time, the wages being paid are somewhat less than during the war period, but not so low as before that period. Cultivation costs vary from $8 to as high as $20 per acre. Pruning, which before the war cost about $12 per acre, now costs from $30 to $35 per acre. For the past season, the rate of 50 cents per tree was quite common in mature orchards. For irrigation the cost varies so greatly in different districts that no general figures can be given. The costs vary from a nominal price in some sections where water is supplied by gravity to as high as $30 to $35 per acre per application, when water must be lifted from great depths. Spray- ing costs about $15 per acre per application. Considerable contract Circular 238] the apricot IN CALIFORNIA 53 spraying at the rate of 3y 2 cents per gallon was done the past season in some districts. When more than one spraying is necessary, the cost is proportionally greater. Thinning cost from $5 to $15 per acre, according to the size of the trees and the amount of fruit set. Digging out borers, probably cost from $3 to $5 per acre. In addition to the preceding expenses, it is necessary to heat some orchards to prevent damage by frost. This involves an additional expense for pots, storage tanks, and the necessary thermometers. The cost for oil in 1921 varied from $8 to $20 per acre, according to the number of times it was necessary to light the heaters. The average cost of picking apricots in the last year or two ranged from $10 to $15 per ton of green fruit, whereas the price was formerly from $3 to $6. "When the fruit is to be dried, about two cutters are needed for each picker. The scale for cutting is approximately from 10 cents to 12 cents per box. From statistics collected in 1916 the estimated cost of drying apricots was $35 to $50 per dry ton. Esti- mates for the same operation in 1920 indicate that $90 to $100 would more nearly approximate the cost. Convenience of arrangement in the dry yard and accessibility to the packing house very materially affect these items. As previously stated, the cost of these various operations in 1921 will undoubtedly be reduced. For drying, more equipment is needed than where the fruit is sold to the cannery. This equipment consists in cutting sheds with suitable tables and benches, sulphur houses, lug boxes, and trays. The cutting sheds are usually inexpensive frame structures, open on all four sides, and are used for storing trays or machinery during the winter. The sulphur houses are constructed either of wood or concrete. The latter are more permanent than the former, but cost more to construct. For a crop of 50 green tons, a minimum of 300 lug boxes are necessary. About 800 to 1200 trays of the 3x8 foot size are ordinarily required for a 50-ton crop. Apricots do require so long a time to dry as prunes, but the harvesting season is shorter. The trays are used two, three, or possibly more times a season, depending upon the rate of drying. The cost of the 3x8 foot trays is about 80 cents to 90 cents a piece. Lug boxes cost from 20 cents to 30 cents a piece. The foregoing items include only the cost of land and labor in bringing an orchard into bearing and harvesting the crop. Equipment, such as plows, harrows, cultivators, pruning tools, and a sprayer must also be provided. The interest and depreciation on these implements, as well as the depreciation on buildings, the taxes and insurance, and the interest on the investment must all be considered in arriving at the cost of production. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. 185. 241. 246. 251. 253. 261. 262. 263. 266. 267. 268. 270. 271. 273. 275. 276. 278. 279. 280. 282. 283. 285. 286. 287. 294. 297. 298. 299. No. Report of Progress in Cereal Investiga- 300. tions. 304. Vine Pruning in California, Part I. Vine Pruning in California, Part II. 308. Utilization of the Nitrogen and Organic Matter in Septic and Imhoff Tank Sludges. 309. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 310. Melaxuma of the Walnut, "Juglans regia." 312. Citrus Diseases of Florida and Cuba 313. Compared with Those of California. 316. Size Grades for Ripe Olives. 317. A Spotting of Citrus Fruits Due to the 318. Action of Oil Liberated from the Rind. 320. Experiments with Stocks for Citrus. 321. Growing and Grafting Olive Seedlings. 323. A Comparison of Annual Cropping, Bi- ennial Cropping, and Green Manures 324. on the Yield of Wheat. Feeding Dairy Calves in California. 325. Preliminary Report on Kearney Vineyard Experimental Drain. The Cultivation of Belladonna in Cali- 328. fornia. 330. The Pomegranate. 331. Grain Sorghums. 332. Irrigation of Rice in California. 334. Irrigation of Alfalfa in the Sacramento Valley. 335. Trials with California Silage Crops for Dairy Cows. 336. The Olive Insects of California. The Milk Goat in California. 337. Commercial Fertilizers. 339. Vinegar from Waste Fruits. Bean Culture in California. 340. The Almond in California. 341. Seedless Raisin Grapes. 342. The Use of Lumber on California Farms. Commercial Fertilizers. A Study on the Effects of Freezes on Citrus in California. I. Fumigation with Liquid Hydrocyanic Acid. II. Physical and Chemical Pro- perties of Liquid Hydrocyanic Acid. I. The Carob in California. II. Nutritive Value of the Carob Bean. Plum Pollination. Mariout Barley. Pruning Young Deciduous Fruit Trees. The Kaki or Oriental Persimmon. Selections of Stocks in Citrus Propagation. The Effects of Alkali on Citrus Trees. Control of the Coyote in California. Commercial Production of Grape Syrup. Heavy vs. Light Grain Feeding for Dairy Cows. Storage of Perishable Fruit at Freezing Temperatures. Rice Irrigation Measurements and Ex- periments in Sacramento Valley, 1914- 1919. Prune Growing in California. Dehydration of Fruits. Phylloxera-Resistant Stocks. Walnut Culture in California. Preliminary Volume Tables for Second- Growth Redwoods. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. The Preparation of Nicotine Dust as an Insecticide. Some Factors of Dehydrater Efficiency. The Relative Cost of Making Logs from Small and Large Timber. Control of the Pocket Gopher in California. Studies on Irrigation of Citrus Groves. Hog Feeding Experiments. CIRCULAES No. No. 70. Observations on the Status of Corn 164. Growing in California. 165. 82. The Common Ground Squirrels of Cali- fornia. 166. 87. Alfalfa. 167. 110. Green Manuring in California. 169. 111. The Use of Lime and Gypsum on Cali- 170. fornia Soils. 113. Correspondence Courses in Agriculture. 172. 115. Grafting Vinif era Vineyards. 173. 126. Spraying for the Grape Leaf Hopper. 174. 127. House Fumigation. 175. 128. Insecticide Formulas. 129. The Control of Citrus Insects. 178. 130. Cabbage Growing in California. 179. 138. The Silo in California Agriculture. 144. Oidium or Powdery Mildew of the Vine. 181. 148. "Lungworms." 182. 151. Feeding and Management of Hogs. 152. Some Observations on the Bulk Handling 183. of Grain in California. 184. 153. Announcement of the California State 188. Dairy Cow Competition, 1916-18. 189. 154. Irrigation Practice in Growing Small 190. Fruits in California. 193. 155. Bovine Tuberculosis. 198. 157. Control of the Pear Scab. 201. 158. Home and Farm Canning. 202. 159. Agriculture in the Imperial Valley. 160. Lettuce Growing in California. 203. 161. Potatoes in California. 205. Small Fruit Culture in California. Fundamentals of Sugar Beet Culture under California Conditions. The County Farm Bureau. Feeding Stuffs of Minor Importance. The 1918 Grain Crop. Fertilizing California Soils for the 1918 Crop. Wheat Culture. The Construction of the Wood-Hoop Silo. Farm Drainage Methods. Progress Report on the Marketing and Distribution of Milk. The Packing of Apples in California. Factors of Importance in Producing Milk of Low Bacterial Count. Control of the California Ground Squirrel. Extending the Area of Irrigated Wheat in California for 1918. Infectious Abortion in Cows. A Flock of Sheep on the Farm. Lambing Sheds. Winter Forage Crops. Agriculture Clubs in California. A Study of Farm Labor in California. Syr-ip from Sweet Sorghum. Helpful Hints to Hog Raisers. County Organizations for Rural Fire Con- trol Peat is a Manure Substitute. Blackleg. CIRCULARS — Continued No. No. 206. Jack Chee§e. 231. 208. Summary of the Annual Reports of the 232. Farm Advisors of California. The Function of the Farm Bureau. 233. Suggestions to the Settler in California. 234. Salvaging Rain-Damaged Prunes. Seed Treatment for the Prevention of 235. Cereal Smuts. Feeding Dairy Cows in California. 236. Methods for Marketing Vegetables in California. Advanced Registry Testing of Dairy Cows. 237. The Present Status of Alkali. Unfermented Fruit Juices. 238. How California is Helping People Ow n 238. Farms and Rural Homes. 239. The Pear Thrips. Control of the Brown Apricot Scale and 240. the Italian Pear Scale on Deciduous Fruit Trees. . 241. 225. Propagation of Vines. 227. Plant Diseases and Pest Control. 242. 228. Vineyard Irrigation in Arid Climates. 243. 229. Cordon Pruning. 230. Testing Milk, Cream, and Skim Milk for 244. Butterfat. 245. 209 210 212 214 215 217 218 219 220 221 223 224 The Home Vineyard. Harvesting and Handling California Cherries for Eastern Shipment. Artificial Incubation. Winter Injury to Young Walnut Trees During 1921-22. Soil Analysis and Soil and Plant Inter- relations. The Common Hawks and Owls of Cali- fornia from the Standpoint of the Rancher. Directions for the Tanning and Dressing of Furs. The Apricot in California. The Apricot in California. Harvesting and Handling Apricots and Plums for Eastern Shipment. Harvesting and Handling Pears for East- ern Shipment. Harvesting and Handling Peaches for Eastern Shipment. Poultry Feeding. Marmalade Juice and Jelly Juice from Citrus Fruits. Central Wire Bracing for Fruit Trees. Vine Pruning Systems.