CALIFORNIA AGRICULTURAL EXTENSION SERVICE CIRCULAR 135 MAY, 1947 OLIVE CULTURE IN CALI FORN IA THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA • BERKELEY Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. 74e PROSPECTIVE OLIVE GROWER t&outet 6tux# t6*t . . . most California olives are more profitably pickled than made into oil. Canned olives do not have much competition from importations. ... it is untrue that the olive will thrive even though neglected. Despite the fact that the tree resists cold, lack of sufficient moisture, and poor soil conditions, the orchard must receive sufficient cultural care, pest control, irrigation, and fertilization, in order to produce valuable crops with fair regularity. . . . alternately light and heavy and sometimes variable crops are apt to be produced by the olive. . . . although olives grow well in a wide variety of California soil types, commercial plantings in coastal regions, on areas poorly drained, on saline soils, or where boron deficiency occurs, are not recommended. . . . figures compiled in 1945 show California had 25,076 acres of olives, with over 19,000 acres located in Sacramento and San Joaquin valleys. In southern California very few new plantings are being made. Cali- fornia produces 99 per cent of the olives in the United States. . . . choice of location is important. Cool, foggy weather does not favor the olive tree, and it is liable to frost injury at temperatures below 10° F. Green fruit will be damaged at about 28° F, but ripe olives will stand a somewhat lower temperature. . . . olives are readily propagated from cuttings or grafting of seed- lings, a process requiring about three years before the trees can be orchard-planted. They come into bearing at about six years of age. Trees already established may be satisfactorily top-worked to new varieties. . . . principal varieties grown in California are the Mission, Manza- nillo, Sevillano, Ascolano, and Barouni. . . . prospective olive growers will do well to plant only varieties known to produce well and conform to processors' needs in chosen localities. CONTENTS PAGE How the olive came to California 5 Botany of the olive 7 Four varieties lead in California 8 Mission 9 Manzanillo 9 Sevillano 9 Ascolano 10 Other varieties 10 Choosing an orchard location 10 District and variety 10 Climate 10 Water supply 13 Soil 13 Processing facilities 13 Propagation and nursery practices 14 Hardwood cuttings 14 Softwood cuttings 14 Rootstocks 14 Growing and grafting olive seedlings 1(5 Top-working 10 Establishing the orchard 18 Spacing 19 Preparation for planting 19 Selection-of nursery stock 19 Planting and care of the young tree 19 Transplanting large trees 20 Intercrops 20 Training and pruning olive trees 20 Management of the orchard 22 Cultivation 22 Irrigation 22 Fertilization 23 Covercrops 24 Production management 24 Alternate bearing 24 Fruit thinning 25 Yields 25 Methods of harvesting 25 Harvesting for pickles 25 Harvesting for oil 27 Diseases of the olive 27 Olive knot 27 Peacock spot, or cycloconium 29 Cercospora spot 30 Boron deficiency, or monkey-face 30 Dieback 30 Soft nose 31 Split pit 31 Insects and other pests 31 Black scale 31 Oleander scale 32 Olive, or parlatoria scale 33 Olive leaf mite 33 Twig borer • 34 Bark beetle 34 Eoot nematodes 34 Handling the crop 34 Economic factors 35 [4] OLIVE CULTURE IN CALIFORNIA IRA J. CONDIT California has approximately 99 per cent of the olive acreage and production of the United States. The total California olive production increased from 9,000 tons in 1921 to 69,000 tons in 1940 and 42,000 in 1944. The only other state having a commercial olive industry is Arizona. About 80 per cent of the olives produced in this country are processed for pickles in various ways, while figures for 1937 and 1938 show only about 0.46 per cent of the total world production of olive oil in the United States. European countries produce 85 per cent of the olive-oil total, Spain leading with 41.5 per cent, followed by Italy with 24.0, Greece with 12.0, and Portugal with 6.0 per cent. Tunisia produces 6.0 per cent and Turkey 3.5 per cent of the world's olive oil. In Spain and in Italy the quantity of olives preserved for consumption as fruit averages only 1 to 2 per cent of the total. Olives are grown both for processing and oil extraction in Argentina, Chile, Peru, and Mexico ; and interest in olive culture in these countries in increasing. California canned ripe olives do not have to meet competition of any simi- lar imported olive product in the United States. Olives are imported as green, pitted and stuffed, or dried Greek style, both oil-cured and brine-cured. The average yearly imports into the United States between 1924 and 1938 were 3,817,944 gallons (5.5 to 6 pounds per gallon) of green olives, 2,444,180 gal- lons of pitted olives, and 260,546 gallons of dried olives. Competition in olive oil is a different matter. For example, the average annual production in California in the period 1920 to 1938 was 282,000 gal- lons of olive oil, but the yearly imports during the same period averaged 17,593,000 gallons. Olive oil is estimated to weigh 7.6 pounds per gallon. The United States import duty on green olives in brine is 20 cents a gallon, on pitted olives 30 cents, on dried ripe olives 5 cents a pound, on olive oil in pack- ages weighing less than 40 pounds, 60 cents, and in larger containers, 49 cents a gallon. Rates of monetary exchange in recent years have tended to nullify these tariffs. HOW THE OLIVE CAME TO CALIFORNIA The olive, Olea europaea, is indigenous to the countries bordering the east- ern end of the Mediterranean Sea, and was introduced into California by Spanish explorers and missionaries in 1769, when Franciscans under Father Junipero Serra and Jose de Galvez came from San Bias, Mexico, to Alta California bringing flower, vegetable, and fruit seeds for planting at the San Diego Mission. Thus the "Mission" variety became established, as cuttings of the olive were taken from San Diego to new locations. Five varieties of the olive grown commercially in California now are, in order of bearing acreage, Mission, Manzanillo, Sevillano, Ascolano, and Barouni. 1 Associate Professor of Subtropical Horticulture and Associate Subtropical Horticul- turist in the Experiment Station, Eiverside. [5] 6 California Agricultural Extension Circular 135 In 1945 the olive stood in twelfth place in acreage of California tree fruits with 25,076 acres in bearing, 2,169 acres nonbearing, and 638 acres in new plantings. Tulare County leads with 7,247 acres, followed by Butte with 4,170, Tehama with 2,675, Sacramento with 1,824, and Los Angeles with 1,600 acres. TABLE 1 California Olives: Acreage by Varieties, by Districts, 1945, and Total Bearing Acreages for 1936 and 1945 District* Ascolano Barouni Mission Manzanillo Sevillano Mis- cellaneous varieties Total Sacramento Valley. 138 254 6,639 832 2,270 385 10,518 Central coast area and foothill 15 2 679 86 44 190 1,016 San Joaquin Valley 479 86 3,427 3,638 429 834 8,893 Southern area 79 41 3,277 592 128 532 4,649 1936 Total 900 456 13,105 5,367 2,619 2,777 25,226 1945 Total 711 383 14,022 5,148 2,871 1,941 25,076 * Districts: Sacramento Valley, north of and including Sacramento County; Central coast and foothill, Sonoma south to San Luis Obispo County and foothill counties east of Central Valley; San Joaquin Valley and San Joaquin County south to Tehachapi Mts.; southern area, Santa Barbara County south to San Diego and Imperial counties. Data from California Fruit and Nut Acreage Survey 1936, 1945, and unpublished estimates of the Cali- fornia Crop and Livestock Reporting Service. TABLE 2 California Production and Utilization of Olives, 1921 to 1945 Year beginning Sept. 1 Total production Canned ripe Other uses Crushed for oil Out-of-state shipments Av. 1921-1925 Av. 1926-1930 Av. 1931-1935 Av. 1936-1940 1 940 tons 11,600 19,200 20,400 38,400 69,000 55,000 57,000 57,000 42,000 30,000 fons 5,920 10,260 7,580 12,120 16,200 16,700 11,100 15,500 13,800 13,900 fons 1,460 2,060 2,900 5,940 12,200 9,600 10,300 12,100 7,800 6,600 fons 3,880 6,400 8,240 19,100 39,100 28,300 34,200 28,600 19,800 9,400 fons 340 480 680 940 1,500 400 1941 1 942 1 943 1,400 800 1 944 600 1 945 100 Data from California Crop Reporting Service, Sacramento. The total acreage in the valley north of and including Sacramento County is slightly larger than that in the San Joaquin Valley (table 1). In southern California, including Santa Barbara and Ventura counties, there are 4,649 acres of olive trees. With 17 per cent of the state acreage, southern California supplies less than 10 per cent of the total production. Olive acreage in south- ern California is declining on account of irregular yields, low returns as com- pared with those of some other tree crops, prevalence of black scale, and increase in real-estate subdivisions. Olive Culture in California 7 Percentages of the crop canned and crushed for oil vary from year to year, utilization depending upon the demand for pickling olives and the price offered the grower (table 2) . BOTANY OF THE OLIVE There are over thirty species of the genus Olea in tropical and subtropical regions of the world, but only 0. europaea is cultivated for its edible fruit. The leaves of the evergreen olive tree are opposite on the stem, have thick cuticle and bear, especially on the lower surface, numerous umbrella-shaped hairs, which serve as protection against excessive loss of water by transpira- tion. Fig. 1. — Clusters of olive flowers with petals removed. First in upper row with plump pistils, rest with pistils abortive or missing. Flower buds begin to form in late summer in axils of leaves of the current season's growth. Actual flower parts are not distinguishable in sections of these buds until March, or approximately 8 weeks before the flowers open and shed pollen. Olive flowers, like lemon flowers, may be either perfect with a plump, green pistil — potentially fruitful — or staminate with a yellow, abor- tive pistil (fig. 1). Olive trees usually bloom profusely, but factors other than the percentage of perfect flowers present, such as vigor of tree and climatic conditions at time of flowering, apparently influence the actual set of fruit. Pollen production of olive flowers is prodigious. While the flowers are open- ing, air currents distribute the yellow pollen throughout the orchard and the flowers are wind-pollinated. Bees visit the flowers primarily to gather pollen. The consensus of opinion in California is that none of the olive varieties grown here requires cross-pollination and that interplanting of varieties is not nec- essary in order to insure greater f ruitf ulness. 8 California Agricultural Extension Circular 135 FOUR VARIETIES LEAD IN CALIFORNIA Growers should plant commercially only the varieties of olives known to produce well and to be favored by the processing plants in the locality. No variety is being propagated and planted commercially in this state for oil production alone. Varieties are still being introduced from other countries and tested in the hope of finding some valuable for certain conditions or uses. ■t § -. f: ^ V Fig. 2. — Typical fruits of olive varieties. Left to right, Sevillano, Ascolano, Manzanillo, Mission (approximately actual sizes). Olive varieties introduced from the Old World and tested in California number several score. In 1894 at the Pomona experiment station of the Uni- versity of California, 66 varieties were being grown. Four years later it was reported that the large pickling varieties attracted especial attention and that growers took nearly all the cuttings then available, especially of Sevillano and Ascolano. Figure 2 shows the four leading varieties in California, the Mission, Man- zanillo, Sevillano, and Ascolano. Olive Culture in California 9 Mission. Olive pits found in adobe bricks of early California mission struc- tures are of variable size and shape, leading to the conclusion that this variety originated through vegetative propagation from an original mixed seedling stock. Cuttings for propagation should be taken only from those Mission trees which have a good production record. The Mission olive tree is vigorous, is upright in habit of growth, and thrives in all olive districts. The fruit (fig. 2) is of medium size, oblique or with a slightly curved axis, and usually somewhat pointed at the apex. The pit is usually asymmetrical, sharply pointed at the apex, and in the mature fruit is free from the pulp. When thoroughly ripe the fruit is blue black in color and attractive in appearance. The Mission starts to ripen about the first of TABLE 3 Analyses of Five Olive Varieties* Variety Samples Olives per pound Per cent of flesh Per cent of oil in flesh number number per cenf per cent Ascolano 5 60 88 14-20 Manzanillo 38 112 106 111 85 82 18-24 Mission 19-29 Nevadillo 57 157 82 22-25 Sevillano 2 36 85 12-18 See G. E. Colby, in California Station Bulletin 123. November in interior valleys, but the fruits mature unevenly and picking may continue for several weeks. The fruits make good oil, are easily processed, and of excellent quality. The oil content varies according to locality and runs from 19 to 29 per cent of the flesh, on a fresh-fruit basis (table 3). Manzanillo. The Manzanillo olive ranks second to the Mission in California acreage. The tree is inclined to a spreading or drooping habit of growth, favoring economical harvesting of the crop. The fruits (fig. 2) are fairly uniform in size and shape and average larger than the Mission. They are oblong, somewhat flattened at the base, and rounded at the apex. The name "Manzanillo" is Spanish for "little apple" and refers to the shape of the fruit. The crop starts maturing earlier than that of the Mission and the fruit is therefore less likely to injury from early frosts. The processed olives are of excellent quality. On account of their size and shape the green fruits are often pitted and stuffed with pimiento. The oil content varies from 18 to 24 per cent (table 3) of the fresh fruit. Sevillano. The Sevillano tree is less vigorous in growth than the Mission but under good cultural conditions is productive of exceptionally large olives. In Spain the variety is extensively grown for green pickling olives known as "Queen." This is not a variety but a trade name denoting any large pickled olive. The fruits (fig. 2) are oval, slightly oblique at the base, and rounded at the apex. The pits are large and prominently roughened over the surface. The fruits are pickled either green or ripe. The oil content is low (table 3) , varying from 12 to 18 per cent of the fresh fruit. 10 California Agricultural Extension Circular 135 Ascolano. The Ascolano, or White Olive of Ascoli, is large in size and a very light green before it takes on the dark-wine color of the mature fruit. The pickled olives are classed as "Queen" by the trade. The fruits (fig. 2) resemble large French prunes in size and shape. The total acreage planted in California has decreased since 1936 and new plantings are not large. Other Varieties. Varieties of olives other than the four just discussed are found in small plantings only. Barouni, a large olive introduced from Tunis in 1905 and widely planted for a few years, produces good crops of very large fruits, but the pickled olives are of woody texture and poor quality. Cuttings of Nevadillo (a variety widely distributed from the Pomona experiment station about 1898) root "almost as readily as willow" and produce trees bearing medium-sized olives good for making oil but not for pickling. Small- fruited varieties such as Pendulina, Uvaria, and Rubra still are found in some of the older California plantings. Chemlali, the principal oil olive of Tunisia, and the Redding bear profusely, but again the very small fruits have value for oil purposes only. CHOOSING AN ORCHARD LOCATION In selecting the location for an olive orchard, several factors should be considered such as district and variety, climate, water supply, soil, and proc- essing facilities. District and Variety. Commercial production of pickling olives over a long period of years has proved certain areas to be successful and shown the adapta- bility of certain varieties to such districts. For example, the Corning district, where the original plantings were largely of the Nevadillo variety for oil production, has gradually developed into the largest producer of Sevillano olives in the state. Butte County has specialized on the Mission olive, and processing plants are equipped to handle the crop both for pickles and oil. Districts adjacent to the deltas of the Sacramento and San Joaquin rivers have many old olive orchards, but new plantings are not so extensive as in areas further removed from the influence of sea breezes and the resulting humidity. The total acreage of coastal counties is small, and no new plantings of any size are being made since crops are seldom entirely satisfactory. Counties of the San Joaquin Valley produce large tonnages of all four com- mercial varieties, but statistics show that of the new plantings Manzanillo is far ahead of all the others in popularity. In southern California very few new plantings of olives are being made. Orchards at Hemet, Blsinore, Fallbrook, and a few other places are being maintained while the demand for olives is good. Production of good crops, however, is apparently more erratic than in hot interior valleys; and few pickling plants south of the Tehachapi depend entirely on the local olive crop for their season's supply. In fact, mature olive trees from some older orchards near the coast have been more profitably sold to contractors for removal bodily to provide ornamental plantings around homes and public buildings. Climate. Olive trees, even when young, are seldom injured by cold weather in commercial olive-growing districts. The Mission tree appears more resist- ant to such injury than trees of other olive varieties. Temperatures as low as Olive Culture in California 11 ■' : . :..'. . v. v- ■ .:■... \. r /M-:-£ ' : ^'&Em : 0k&;:r ■>; ,:•: :$>%ZW': -Ml-.\ % :V::k "^ *^&a^m Fig. 3. — Border olive trees sometimes reach large size. Note how these trees tower above the man standing near them. 12 California Agricultural Extension Circular 135 -The trees of many olive varieties are characterized by large swollen bases and by bulging excrescences or "ovuli" on the trunks. 15° to 16° F cause little if any injury to foliage or wood. Lower temperatures are often fatal to tender twigs and may cause a cracking of the bark on small branches. Such injury favors the spread of the bacterial disease known as olive knot. Severe injury to mature trees is likely to follow a drop in tempera- ture to 10°. (Ireen olives are susceptible to frost injury at about 28° F, but ripe olives will withstand temperatures somewhat lower. Frozen olives may be used for oil production. Orchard heating has not been practiced to any extent for olives since loss of fruit because of frost hardly justifies installation of heaters. Olive Culture in California 13 During the flowering season of olive trees in late April and early May, weather conditions generally are favorable for pollination, although occa- sional rain may injure some of the flowers. Cool foggy weather is not favorable to proper development or pollination of flowers. In some seasons sudden hot spells occur in June and cause serious shedding of the young fruits. Dry winds in late summer sometimes cause olives to shrivel, and such fruit may drop and be lost. If such olives remain on the tree, they can be used for oil purposes. In case there is sufficient moisture in the soil and air temperatures are not high, shriveled olives usually regain their natural plumpness. Water Supply. Olives can be produced in California without supplementing the natural rainfall with irrigation water; but oil varieties only should be considered for unirrigated lands, and trees should be spaced far apart. In Tunisia, where the rainfall is 8 to 14 inches, Chemlali olive trees are planted 65 to 80 feet apart, or 7 to 10 trees per acre. Since the olive industry of California is based primarily on production of large fruit for pickling, a supply of irrigation water is one of the essentials to success. Fruit does not size up properly unless a certain amount of soil mois- ture is available, as further discussed under irrigation. Unfortunately, the idea became prevalent in the early days of olive culture in California that olives would thrive under neglect and produce fruit on dry hillsides where cultivation was impossible. Soil. The apparent success of olive trees on shallow, poor, or rocky soils does not indicate their preference for such soils. Trees planted on deep, rich soils may reach such a large size as to make fruit harvesting both difficult and costly. The olive tree thrives on dry bog soil in Tulare County, on hardpan lands if the hardpan is shattered by subsoiling or blasting, on the decomposed granite soils of the foothills, on clay soils in Butte County, on silt and gravelly loam in Tehama County, and on the sandy soils in southern California. The trees do not tolerate poor drainage nor the presence of standing water for any long period. Sickly trees in low, wet spots are seen in many olive districts. Saline soils should be avoided for olive culture. Even though olive trees may seem to thrive on soils where orange trees have succumbed to salt injury, profitable returns cannot be expected to continue from trees on such soils. The presence of injurious salts in the soil is closely associated with a high water table and poor drainage. Planting of olives in such locations should be avoided. The kind of salt in the soil is of more importance than the total amount. Trees will tolerate a considerable amount of sulfate or white alkali in the soil but may be seriously injured by a relatively small amount of sodium carbonate, or black alkali. A deficiency of boron in the soil has resulted in twig, leaf, and fruit injury to the olive in some California districts. Processing Facilities. The necessity of growing olives in the immediate vicinity of a processing or packing plant is not so important as it is with certain more perishable fruits. Green and ripe olives are successfully trans- ported long distances from the orchard before being graded or pickled. Furthermore they are commonly stored in holding solutions for long periods, after which they can be processed. Friendly cooperation between growers and processors, however, is desirable, and this can best be accomplished when distances are not great. 14 California Agricultural Extension Circular 135 PROPAGATION AND NURSERY PRACTICES Olive trees are propagated either from cuttings or from seedling rootstocks grafted to the desired variety. Prospective growers are usually dependent upon commercial nurseries for a supply of trees. Some common methods of olive propagation are here discussed. Hardwood Cuttings. Cuttings of olive branches of almost any size and age will grow if properly planted. As older cuttings generally require a longer time to form roots and sprouts, the hardwood cuttings are not so commonly used as in former times. Cuttings about V4 inch in diameter and 6 to 8 inches long, made in February and put in sand with bottom heat, form roots and make a short growth by fall. They can then be planted in nursery rows and transplanted to the orchard at the end of the second or third season's growth. Softwood Cuttings. Most large nurseries use small herbaceous cuttings because of economy of material, economy of space during early period of propagation, and more rapid formation of roots and hence earlier transplant- ing of rooted cuttings. -This method is as follows. Leafy twigs which have completed their growth and become firm by October are cut into 5-inch lengths with the basal cut just below a node. The two lower leaves are entirely removed and remaining leaves cut back one half. Cuttings are immediately placed in sand, preferably with bottom heat and with humidity kept relatively high by meansof a glass cover- ing for the cutting bed. Some nurserymen use flats 4 inches deep each holding about 150 closely set cuttings. Clean, sharp sand free from organic matter should be used and kept moist but not too wet. A temperature of 65° to 70° F is favorable to the rooting process. Roots may form in from 8 to 10 weeks, but the cuttings should be left in the bed or flat several weeks longer until roots are well developed. Cuttings planted in October should be ready to be set in nursery rows by the middle of May. Trees should be of proper size for transplanting to the orchard at the end of two years in the nursery row. Olive trees begin to bear at about six years of age. Experimental treatment of herbaceous cuttings (fig. 5) with root stimulat- ing substances such as indole butyric acid at 25 to 50 parts per million, indicates marked beneficial results with Mission, Manzanillo, and Sevillano varieties (according to unpublished data furnished by H. T. Hartmann). Rootstocks. The relative success of an olive variety on its own roots as compared to the same variety grown on a seedling stock has not been definitely established by careful orchard trials. Thousands of Mission and Manzanillo trees grown from cuttings have proved excellent producers, but for some varieties, such as the Sevillano, seedling rootstocks are commonly used. The small-fruited Redding olive has been selected as stock since the seeds are practically 100 per cent viable and the seedlings vigorous in growth. Natural seedlings of different varieties can generally be pulled up by the hundreds from the rain-soaked soil under old olive trees. A nurseryman, however, should be able to certify and the grower who buys trees should have the satisfaction of knowing what stock has been used in propagation. Grafting of olive seedlings is practiced largely as an aid to rapid propagation. The graft union on the Olive Culture in California 15 Fig. 5. — Effect of a root-stimulating substance on Mission olive cuttings after 10 weeks in sand: A, check (no treatment) ; B, cuttings soaked for 24 hours in 50 parts per million or indole butyric acid. (Photo by H. T. Hartmann.) nursery tree is generally at or below the ground surface, and some roots eventually grow from the scion as well as from the stock. Different members of the olive family can be grafted on the olive tree with varying degrees of success. Species of Olea such as 0. chrysophylla, 0. ferru- ginea, 0. verrucosa unite perfectly and may have value as rootstocks. Olea cuspidata and 0. glandulifera have been used experimentally as stocks in 16 California Agricultural Extension Circular 135 India. The olive has been successfully grafted on the common lilac, on species of Fraxinus, or ash tree, and on California wild olive, Forestiera neo-mexicana. This Forestiera and related species have possible value as dwarfing stocks for vigorous olives such as the Mission. Some species of Ligustrum, or privet, will grow on the olive but none shows promise of making a good rootstock. Growing and Grafting Olive Seedlings. 2 The growing of olive seedlings is a fairly simple nursery procedure. The seed, freed from pulp, is placed in a 15 to 25 per cent brine ; floating seeds are rejected as sterile. The hard shell of the fertile seeds is cracked or the apex removed by means of a notched clipper. Seeds are planted in flats of soil and the seedlings should appear in 4 or 5 months. When 5 inches high they are transplanted to paper pots and held until spring, when they are planted in nursery rows. Under favorable grow- ing conditions the seedlings should be ready for grafting two years from the time the seed was planted. Bark grafting is the usual method in working over the seedlings if they are growing in the nursery row. This method is as follows : cut stock off an inch or two above the surface of the ground ; slit the bark on one side vertically ; insert the scion of desired variety cut to a long single bevel, underneath the slit bark ; tie firmly with raffia or string ; cover exposed parts with grafting wax. Seedlings grown for the purpose or Fig. 6. — Patch bud on olive branch. Note sprout starting to grow from upper edge of patch. natural seedlings 14 to % inch in diameter can readily be bench-grafted. Seedlings are prepared in large numbers by cutting top and root each about 4 inches in length. Fresh scions of the proper size are then whip-grafted onto the stock and tied with string. The grafts are stored in sand or sawdust for a period of callusing before being planted in the nursery row. Pieces of olive roots !/4 inch in diameter and 5 or 6 inches long can be whip-grafted in the same way. Shield budding of olive seedlings is not so successfully practiced as with citrus seedlings. Twig buds or very small scions inserted in T-shaped incisions in the stock have been used for propagation. Top-working. Olive trees may be top-worked by any one of several different methods, which fall into two general classes, budding and grafting. In bud- ding (fig. 6) shield buds do not give such good results as patch buds. A patch 2 Bioletti, F. T., and W. F. Oglesby. Growing and grafting olive seedlings. California Agr. Exp. Sta. Bui. 268:303-26. 1916. (Out of print.) Olive Culture in California 17 of bark 1 inch long and % inch wide with a dormant bud in the center is removed from a one-year-old branch of the desired variety. An I-shaped cut of the same length as the bud is made in the stock, the two flaps loosened, and the patch bud inserted under the flaps of the I. The flaps are tied firmly with budding tape or soft twine to be left 2 or 3 weeks before removal. If the patch has united with the stock, it will be green and fresh looking; the stock should then be notched or girdled an inch above the bud to force the latter into growth. Fig. 7. — Olive tree top-worked by bark grafting. Exposed bark has been whitewashed but no safety branch left. Bark grafting (figs. 7 and 8) is the method most commonly used for top- working olive trees. The work can best be done in spring when the bark is slipping well. The main branches of the tree are first cut back to stubs. Scions approximately % inch in diameter and 4 inches long are cut with a long bevel on one side and a very short bevel on the other ; sometimes a shoulder is cut at the upper end of the long bevel in order to seat the scion firmly over the cut edge of the stock. Scions are inserted by any one of various methods. The common practice is to make a single vertical slit in the bark of the stock, open the edges of the slit bark slightly, then push in the scion full length on the long bevel. The scion is tied firmly with cotton string or tape, then the cut surfaces are waxed. Some prefer to tack the scion and even the loose bark to the stock with small flathead wire nails before tying. Scions can also be inserted without slitting the bark. One method is to wrap a cloth band firmly 18 California Agricultural Extension Circular 135 around the cut end of the stock, allowing the band to project about Vi inch. The scion is pushed or tapped into place after the bark has been slightly loosened with a blunt knife or other instrument. Bark grafts are sometimes inclined to grow vigorously and to become top- heavy so that they break out in windy weather. Long growth should be cut back. It may be necessary to support the scion growth by stakes tied or nailed Fig. 8. — Olive scions one year old growing on a 30-year-old stump. (Photo courtesy of U.S. Department of Agriculture.) to the trunk and framework branches. Exposed bark of the stock should be protected from sunburn by whitewash. It is advisable to leave at least one nurse, or safety, branch on the stock for the first two years or until the scions are well established. In case the bark grafts do not start properly, suckers from the framework branches can be selected and whip-grafted to the desired variety. There is less danger of breakage in such grafts than in bark grafts. ESTABLISHING THE ORCHARD The steps necessary to prepare land for planting olive trees are not essen- tially different from those taken for other fruit trees. Wherever possible the land should be graded to a uniform slope so as to facilitate the distribution of water. Planting of hillside orchards on contours or terraces will help to Olive Culture in California 19 prevent erosion. The irrigation system should be installed before the trees are planted although it is generally practicable to water from a tank wagon during the first year. Other factors to be considered by a prospective grower are spacing of trees, preparation for planting, selection of nursery stock, planting and care of young trees, transplanting of large trees, intercrops. Spacing. Most olive growers prefer to plant trees by the square system, the spacing depending upon the soil and the variety. Experience has shown that closely planted trees, 20 x 20 feet for example, generally become crowded a few years after they reach bearing age ; the lower branches die off from lack of light, and fruit production is limited to upright branches in the top. The standard spacing of Sevillano trees in the Corning district is 22 x 22 feet, but many growers are favoring a wider spacing of new plantings. Mission and Manzanillo trees should be spaced at least 36 feet apart, Some plantings have been made with the rows 40 feet apart and the trees spaced 20 feet in the row. This system is satisfactory while the trees are young, but alternate trees will eventually have to be removed. Size of tree can be regulated to some extent by pruning. Wider spacings provide better facilities for cul- tural operations, pest control, and crop harvesting. Preparation for Planting. Stakes for tree holes are set by means of a plant- ing wire or chain, or sometimes by sighting across properly placed end stakes. Holes are dug a short time before the planting. In old grainland a good pro- cedure is to subsoil deeply both ways, the subsoiler being pulled along the tree rows and trees planted where the furrows intersect. Lands having a distinct stratum of hardpan a short distance below the surface are prepared for planting by subsoiling or by blasting for each tre^ hole in late summer when the ground is dry enough to shatter or crack. After the ground is blasted, chunks of hardpan should be removed and the hole filled with top soil. After winter rains the land is restaked and tree holes dug as usual. Selection of Nursery Stock. Olive trees are dug from the nursery after two seasons' growth and separated into grades based on caliper measurement, or diameter, of trunk. With branches entirely removed and with bare roots they are heeled in in trenches of well-drained soil until planting time. Medium- sized trees % to % inches in diameter with good root systems make good planting stock. Planting and Care of the Young Tree. Nursery trees may be planted during the winter months if the soil is sandy and well drained. On heavy soil it is better to delay planting until spring because the newly planted trees might be injured by standing water. The method of planting an olive tree differs very little from that used for any other fruit tree. Especial care should be taken to prevent exposure to the sun and drying out of the roots during the various steps in the transfer of trees from the nursery to the orchard. A very good practice is to use a low planting wagon equipped with tanks or tubs containing thin mud in which the roots are kept immersed or puddled. Trees should be planted the same depth they stood in the nursery row, for bark-rot injury may result from deeper planting. At the time of planting, the roots should be trimmed and all mangled roots cut back to healthy wood. Tree holes need to be only large enough 20 California Agricultural Extension Circular 135 to contain the roots without crowding. While one person holds the tree in place and firms the soil with his feet, another shovels topsoil into the hole until it is level full. Irrigation usually follows planting. Whitewashing the exposed trunks or using veneer tree protectors is a wise precaution in order to avoid sunburn. Transplanting Large Trees. It is sometimes possible to start a new planting with olive trees transplanted from orchards already established. This is prac- ticable only if the work is well organized, if only medium-sized trees are moved, and if labor costs are not excessive. The following procedure has given good results. In October dig a trench around the tree 2 feet from the trunk, sever lateral roots and refill with soil. Cut the top back to short stubs and whitewash exposed bark. In March open the trench, cut taproots, and drag the tree, with a ball of dirt if possible, onto a low sled. Haul the tree to the new site, replant immediately in a hole already prepared, and water freely. One grower re- ported transplanting twelve-year-old trees and losing only 10 out of 1,612 thus moved. The use of power outfits should materially reduce the cost of transplanting large trees. Trees with the tops cut back can be lifted from the ground with a stump puller and transplanted bare-root. Such work should be done, if pos- sible, in midwinter. Intercrops. Intercropping of young olive orchards is sometimes practiced. The grower may decide to double-plant, that is, set twice the number of olive trees which will eventually remain. This is a dubious practice, for the olive is comparatively slow coming into full production, and when that stage is reached the grower is loath to remove interplants. The system may be advis- able if the alternate trees are transplanted as just described. The planting of alternate rows of two olive varieties, such as Mission and Manzanillo, for possible cross-pollination purposes is not a good practice. Neither is it neces- sary to plant pollinator trees throughout the orchard as has been commonly done in some districts. There are few annual crops which can be profitably grown between young olives trees. Peach, apricot, or plum trees, which come into bearing early, may be planted in the more widely spaced orchards and provide a source of income for a period of ten to fifteen years. But no intercrop should be allowed to hinder the best development of the olive trees. Training and Pruning Olive Trees. Newly planted olive trees should be cut back to from 24 to 30 inches above the ground. At the end of the first growing season, from 3 to 5 laterals are selected to form the framework branches, these to be spaced as widely as possible on the upper 10 inches of trunk. No heading back of new growth in necessary. Pruning at the end of the second, third, and fourth season is simple and consists only in removal of cross limbs and crooked or broken branches. The aim is to leave as much foliage as possible. Staking may be necessary for crooked trees or those blown over by wind. Experiments on pruning young olive trees 3 have shown that pruning retards the growth of young trees ; excessively heavy pruning as some- 3 Bioletti, F. T. Pruning young olive trees. California Agr. Exp. Sta. Bui. 348:87-110. 1922. (Out of print.) Jacob, H. E. The effect of pruning in the training of young olive trees. California Agr. Exp. Sta. Bui. 568:3-26. 1934. Olive Culture in California 21 times practiced retarded their development as much as 90 per cent. Trees left unpruned until five years old bore heavier crops in the fifth season than did the pruned trees. Crops during the sixth and subsequent years were about the same on trees of each of the four varieties under all systems of pruning except the severely heavy system. Severely pruned trees did not produce a crop of commercial importance during the seven years of the experiment. Spreading branches of young Manzanillo trees are sometimes held in a horizontal position by bands of burlap and by internal bracing of framework x Fig. 9. — Some growers reduce the height of Mission olive trees by removing central upright branches and by preserving the spreading or drooping branches. branches by means of twine and screw eyes attached to the branches. In experi- mental trees there was a marked improvement in shape of the braced trees for at least five or six years. At seven years of age, however, the difference between the trees which had been tied and those not tied was not great. It appeared doubtful that any permanent improvement resulted from the tying. Experiences of growers and results of pruning experiments on bearing olive trees have shown that the drastic pruning practiced in parts of the Old World and in some orchards of California is detrimental to fruit production. It has long been believed that olive trees should be kept open so that light and air could readily penetrate. Some orchards, however, have been left unpruned for a decade or more with no detrimental effect on yield or quality. The Tulare County Farm Advisor's office suggests that moderate to light pruning of olive trees each year provides conditions for easier harvesting of the crop with less scarring of fruits, reduces hazard of limb breakage, and increases efficiency in pest control. Advantages of pruning are obtained at 22 California Agricultural Extension Circular 135 relatively high cost in terms of labor expense plus crop reduction. But condi- tions of labor shortages for harvesting olives and the increasing necessity for effective pest control, may now justify regular pruning in orchards where formerly pruning was considered less essential or even unprofitable. Other suggestions were as follows : A program of annual light pruning is preferable to more severe pruning at longer intervals ; as much of the low-hanging, out- side f ruitwood should be left as possible ; excessively tall limbs should be cut back to strong laterals ; when in doubt as to whether a cut should be made, the branch should be left for next year. It is sometimes desirable to reduce the size of large olive trees, especially Mission, by cutting the framework branches to short stubs as for grafting. Loss of crop naturally results if the whole top is cut back at one time. Transforma- tion of the tree can be accomplished gradually by cutting one or two branches only each year. MANAGEMENT OF THE ORCHARD Cultivation. The major purposes of cultivation are to facilitate the distribu- tion of irrigation water, to incorporate organic matter with the soil, and to eliminate the competition of weeds for available soil moisture. 4 On rolling, uneven land it is a common practice to ridge up the ground into contour checks so as to prevent runoff or washing of soil in periods of heavy rainfall. Spring plowing or disking to turn under the covercrop, either natural or planted, and light cultivation as often as necessary to destroy weeds are the usual practices. Olive trees are shallow-rooted, and the root system may be seriously injured by deep or excessive cultivation. The practice of subsoiling between tree rows is seldom justified. Frequent cultivation of wet soil packs it and forms a plow- sole which makes penetration of water difficult. Two systems of noncultivation are applicable to olive orchards. The first, used in some northern California districts, utilizes permanent irrigation furrows and allows a permanent covercrop of weeds, grass, or alfalfa to grow between the trees. This crop is mowed at intervals to reduce the fire hazard. In the second system, permanent furrows are formed and weeds are kept in check by spraying them with a weed killer. In the Sevillano olive-production management study of Tehama County for 1941 appears this statement : "Cultivation appears to be unimportant so may well be omitted or kept to a minimum." Irrigation. The olive is a drought-resistant tree. 5 Neglected trees are able to adapt themselves to their environment and to keep in remarkably good vegeta- tive condition for long periods. During periods of low prices of olive products, growers commonly leave orchards unirrigated, unfertilized, and unpruned. Such a practice, which would be fatal to most fruit trees, is productive of little if any fruit, but does maintain the olive trees in such a condition that with good care they can be brought back into profitable production within two or three years. In order that an olive orchard may produce good crops of 4 Veihmeyer, F. J., and A. H. Hendrickson. Essentials of irrigation and cultivation of orchards. California Agr. Ext. Cir. 50 : 1-24. Eevised 1943. 5 Mason, S. C. Drought resistance of the olive in the southwestern United States. U.S. Bur. Plant Indus. Bui. 192:1-44. 1911. Olive Culture in California 23 pickling-size fruit with fair regularity, however, it is necessary to keep the root system well supplied with water throughout the year. Total seasonal water requirements of trees depend upon climate, size of trees, root distribution, soil type, and somewhat upon variety. Some oil vari- eties of olive will produce satisfactory crops under conditions which would make pickling olives unproductive. Few, if any, cultural practices in olive orchards are less standardized or understood than the time of application and the amount of irrigation water to be used. Orchards in cool coastal districts may require less than half the water required by trees of the same size in hot interior valleys. In the foothills, where most of the roots are found in the first 2 or 3 feet of soil, irrigations should be more frequent than in valley soils, where roots extend deeper. Periodic examination of soil moisture with a shovel, an auger, or a soil tube to the bottom of the root zone, and application of water before the wilting point is reached are two of the prime requisites to success in the culture of pickling olives. In Tulare County in 1941 and 1942, the average amount of irrigation water used per acre was 40 to 41 acre-inches, about 10 inches more than for citrus trees in the same period. Methods of applying irrigation water in olive orchards are not essentially different from those used in other orchards. After the spring cultivation, furrows may be made and used for two or three irrigations before weed growth makes cultivation again necessary. Fertilization. Fertilizer trials in bearing olive orchards have shown that the trees often respond to application of nitrogen. Since the natural supply of nitrogen in California soils is low or soon becomes so with the growth of cultivated crops, it is necessary to make up the deficiency with manures or with chemical fertilizers. Animal manures are slow in action but are beneficial if sufficiently large amounts are used and the cost is not excessive. The fer- tilizer which provides the most nitrogen for the least money should be used. Recommendations made as result of a fertilizer experiment in the Corning district with Sevillano trees planted 22 x 22 feet follow : For orchards in poor condition apply 1 pound of actual nitrogen per tree in February or March ; continue this practice for two years watching carefully that quality and time of ripening of the olives are not too greatly affected ; in each ensuing year apply % pound of nitrogen per tree; add manures if available at a reasonable cost ; grow one or two green-manure crops between the trees each season. For orchards in thrifty condition, follow the same pro- cedure but omit the first two steps. Nitrogen application reduced the percent- age of large fruits, but the greater total yield resulted in greater production of both larger and smaller sizes. Similar experiments conducted in Tulare County on mature Manzanillo trees suggest the following program : For an orchard in poor condition, apply 100 to 150 pounds of nitrogen per acre per year for the first few years, then reduce the amount of nitrogen to from 50 to 75 pounds per acre per year. For an orchard in good condition maintain an annual program of at least 50 pounds of nitrogen per acre per year, and apply double this amount in the heavy-crop years to aid in obtaining a crop in the "off-crop" years. Response 24 California Agricultural Extension Circular 135 to fertilization was in thriftier growth of the tree and the setting of larger numbers of fruits, with a tendency to higher gross yields by greater numbers of fruits rather than larger sizes. No difference in time of maturity was noted in Tulare County between fertilized and unfertilized plots ; both were har- vested on the same dates. In Tehama County fruits on fertilized plots ripened as much as 2 weeks later than fruits on the unfertilized plots. A boron deficiency in soils of certain olive districts causes some twig, leaf, and fruit injury. 6 Short bunchy growth of twigs due to the death of terminal buds is characteristic of affected trees. Smooth protuberances with dead tissue beneath appear on the bark. At the end of the growing season leaves become pale green and even bright yellow towards the apex. Fruits become pitted and malformed, especially at the apex, and are referred to as "monkey-faces." Treatment consists of the application of 1 pound of borax to the soil around each affected tree. Covercrops. Covercrops are commonly grown in orchards to improve the physical structure of the soil, to increase the rate of water penetration, and to prevent soil erosion during the rainy season. The amount of organic matter actually added by a covercrop is exceedingly small. Decomposition of the added organic matter is of greater importance than its accumulation. The kind of covercrop to be planted is decided from local experience. A natural growth of weeds and bur clover often provides a good tonnage of green man- ure. Legumes such as sweet clover, vetch, or field peas may add small amounts of nitrogen to an impoverished soil. The tendency now is to plant mustard or any other crop which will grow well in cool weather and provide the maximum tonnage of green matter to be incorporated into the soil in the spring. Applica- tion of a nitrogenous fertilizer may be necessary to secure a good growth of mustard or other crop. Irrigating orchard soil may be necessary in the fall to get a covercrop started and again in dry periods during the winter to keep it growing vigorously. The covercrop should not be allowed to deplete soil mois- ture to the detriment of the trees. PRODUCTION MANAGEMENT Production management studies 7 of the olive show that some orchards yield several times as much fruit as others on similar soils and under the same climatic conditions. High yield is by far the most important profit-determining factor. An olive grower should, therefore, consult his county farm advisor on cultural matters and learn what methods are likely to increase production or maintain it at a reasonably high level. Alternate Bearing. Alternate bearing is not a trait peculiar to olive trees, but it is especially pronounced in this tree crop. Alternate light and heavy crops are particularly serious in packing-house and marketing operations, 6 Scott, C. E., H. Earl Thomas, and Harold E. Thomas. Boron deficiency in the olive. Phytopathology 33 : 933-41. 1943. 7 Shultis, Arthur, and Dave Williams. Fifth annual and final report Sevillano olive pro- duction management study Tehama County. 12 p. California Agricultural Extension Ser- vice, Berkeley, Calif. (Mimeo.) 1942. Moore, E. C, and A. Shultis. Second annual summary olive management study for Tulare County. 9 p. California Agricultural Extension Service, Berkeley, Calif. (Mimeo.) 1942. Olive Culture in California 25 where a regular supply of pickling-size fruit is preferred. Reference to the figures in table 1 (page 6) shows that there may be periods when moderate crops follow one another. Two heavy crops do not come in successive years ; a heavy crop is very liable to be followed by a light one. Pruning seems to have no effect in overcoming alternate bearing. Thinning fruit in a heavy crop year alleviates the strain upon the tree and has a tend- ency to promote regular bearing. Extra heavy applications of nitrogenous fertilizers to trees in the heavy crop year will help size up the fruit and at the same time stimulate production of new wood on which a crop will set the following season. Careful attention to irrigation, fertilization, and other cultural details' should be given. Fruit Thinning.* Experiments conducted about twenty years ago in hand- thinning of olive fruits tended to show that this practice increases the size of the fruit, brings about earlier ripening, decreases the danger of loss from frost and from shriveling, and reduces the tendency to alternate bearing. The thinning is done in the period between June 15 and July 15 before the fruit pits harden. In actual practice both hands are used with the fingers taped for protection, and the small olives stripped from several twigs at one time. The objective is to leave an average of 2 or 3 olives per foot of twig. Thinning is favored only by a few growers who have moderate-sized trees, who aim to produce a large proportion of pickling sizes, and who believe the practice will favor regular production of crops. High prices for oil olives tend to remove the incentive to produce fruits of large sizes. Yields. Records of production on 471 acres of olive orchards in Tulare County during the heavy-crop season of 1940-41 show the following averages : Manzanillo, 5.98 tons per acre ; Mission, 7.52 tons ; Sevillano and Ascolano, 6.31 tons. The following season 1941-42 production was lighter : Manzanillo, 4.28 tons per acre; Mission, 2.86 tons; Sevillano and Ascolano, 3.65 tons. As sometimes happens, a greater income was secured in the light-crop year because of higher prices paid for the fruit. Records of yield of twelve Sevillano orchards in Tehama County over the five-year period 1938 to 1942 show an average production of 2.39 tons per acre. One orchard showed an average yield of 5 tons per acre during the same five-year period. Other orchards averaged 3 tons per acre with a higher per- centage of grades 1, 2, and 3. METHODS OF HARVESTING Harvesting for Pickles. Olives for green pickles are harvested when they are mature and of full size and as they turn from a deep-green to a light-green color. In the harvesting of ripe olives, picking practices vary. Some proces- sors want fruit of a straw-yellow color ; others prefer it well colored. Pickling olives must be handled carefully, for bruised fruit causes defects in the finished product. Stripping olives from the tree is sometimes practiced, but most olive buyers insist on having the fruit carefully hand-picked. 8 See: Drobish, H. E. Olive thinning and other means of increasing sizes of olives. Cali- fornia Agr. Exp. Sta. Bui. 490:3-20. 1930. (Out of print, but may be consulted at many libraries.) 26 California Agricultural Extension Circular 135 Tig. 10. — Olives being harvested in October. Olives for pickles are picked by hand into buckets suspended from the shoulders ; oil olives are commonly beaten from the trees with poles and picked up from the ground. (Photo courtesy California Foods Eesearch Institute.) Olive Culture in California 27 A list of equipment used in the harvest includes ladders, picking buckets or bags, hooked sticks, lug boxes. Ladders for olive picking are the longest used in any fruit harvest ; they are made with or without a third leg. Buckets strapped to the body to permit use of both hands are commonly padded. Picking bags, the lower end of which can be opened to release the fruit, are also used. Olive harvesting is generally piecework, the picker being paid according to the number of lug boxes he picks each day. Harvesting for Oil. Oil olives are left on the tree until they are fully colored and have a maximum content of oil. Except for loss of fruit through dropping, harvesting can proceed over a long period in late fall and early . ■■ Fig. 11. — Olive-knot tubercles on branch. (Photo by R. E. Smith.) winter. However, four seasons' experiments in Tulare County with both Mission and Manzanillo trees showed that delayed harvesting caused an aver- age reduction of 45 per cent in the crop of the following season as compared with similar trees harvested early for pickling olives. Oil olives are commonly beaten from the trees with sticks or poles and picked up from the ground or collected on sheets of canvas. This method economizes on labor but bruises the twigs and knocks off leaves and small branches. Stripping the olives from the tree with the fingers or by the use of small rakes results in less tree injury. DISEASES OF THE OLIVE The olive tree and its fruit are subject to a number of injurious diseases in California. The most important will be briefly discussed. Olive Knot. The bacterial disease known as olive knot (fig. 11) is wide- spread in the interior valleys of California north of the Tehachapi. A survey made in 1934 showed that only 0.5 per cent of Tulare County olive trees were infected with the knot. Of commercial varieties, the Mission is the least susceptible to infection. During wet weather, bacteria are exuded to the sur- face of knots, from which they are spread downwards by drops of water and laterally by wind-borne particles of rain. Wounds are apparently necessary for infection. Frost cracks, pruning 28 California Agricultural Extension Circular 135 f »# « .. < < • 5 ; Fig. 12. — Peacock spot or cycloconium on Mission olive leaves. (Natural sizes.) Olive Culture in California 29 wounds, scars following drop of leaf- and fruitstalks, and bark cracks due to emergence of suckers, are common avenues for entry of bacteria. If infection occurs in midwinter, actual knots do not appear until spring. They gradu- ally form rough, roundish galls or swellings, sometimes several inches in diameter, on twigs, branches, trunks, roots, or even on leaf petioles and fruit- II Fig. 13. — Symptoms of boron deficiency in olive leaves. (Photo by C. E. Scott.) stalks. If uncontrolled, olive knot restricts sap movement, causes branches to die, and generally interferes with healthy tree growth and good fruit pro- duction. Control consists in cutting out the galls carefully with chisels and then disinfecting the cuts and tools with a solution of corrosive sublimate 1 part to 1,000 parts of water, used only in wooden or glass containers. A 4 to 5 per cent solution of formalin is also a good disinfectant. Infected twigs and small branches should be removed. Since the bacteria are inactive on the knot sur- faces during the summer months and no rain falls to spread the bacteria, prun- ing of olive trees during those months is being advocated in some districts. Peacock Spot, or Cycloconium. The name "peacock spot" comes from the fact that the disease produces large, vivid spots (fig. 12) on the normally green leaves of olives trees. Affected leaves turn yellow and fall prematurely, 30 California Agricultural Extension Circular 135 the drop sometimes being so severe that the tree fails to grow and fruit prop- erly. The fungus, Cycloconium oleaginum, has long been known to occur on olives in California, but only in recent years has attention been called to its seriousness. Atmospheric humidity favors the development of the fungus, since the spores are spread in drops of moisture. A 5-5-50 bordeaux-mixture spray applied twice in the season, in November or about the time of early rains and in April or May, is recommended in badly affected orchards. fi^P fk Fig. 14. — Effect of boron deficiency on olive fruits. (Photo by C. E. Scott.) Cercospora Spot. Purplish-black spots caused by a species of Cercospora have been found on green olives in Solano and San Diego counties. Affected olives can be used for ripe pickles but not for green processing. Bordeaux spray will probably control this disease, although it has not become sufficiently widespread to cause serious loss of fruit. Boron Deficiency, or Monkey-Face. This disease is apparently restricted to certain localities and has been most common in the olive districts of Butte County. It has recently been shown to be due to a deficiency of boron in the soil, which causes a dieback of twigs, yellowing of leaves (fig. 13), and defec- tive fruits. The affected fruits (fig. 14) have had the names "monkey-face," "sheep nose," and "shrivel-tip" applied to them. This disease is further de- scribed under fertilization on page 24. Dieback. Dying-back of olive branches is a common occurrence in many orchards. Branches up to 1 inch in diameter will sometimes die back to a sharp line which separates the live and the dead wood. Various causes, such as Yerticillium, or deficiency or excess of certain chemical elements, may account for the dieback, so that each case should be considered by itself and diagnosed accordingly. Olive Culture in California 31 Soft Nose. A fruit trouble known as soft nose (fig-. 15) affects mainly the Sevillano variety, causing the fruit to turn dark at the apex and shrivel. It is worse on young trees than on older ones and is thought by some to be intensified by heavy nitrogen fertilization. Since the trouble is nonparasitic and occurs only in occasional years, no control measures are suggested. H m Fig. 15. — Soft nose, or blossom end rot, of Sevillano. Normal fruit at left. Split Pit. Sevillano olives, which are normally broadly conical at the apex, sometimes appear bluntly flattened. When such fruits are sectioned, the pit is found to be split into two more or less equal parts. This appears to be a variety characteristic, the nature of which is obscure. INSECTS AND OTHER PESTS The olive is seriously attacked in California by three scales : the black, the oleander, and the olive, or parlatoria. 9 Black Scale. Black scale, Saissetia oleae, is the most important and wide- spread of olive insects. Hot, dry weather kills large numbers of the young black scale, but the pest is becoming more and more serious. Damage is done not only by the scales which feed on twigs and leaves, but also by the black fungus which grows in the honeydew excreted by the insect. The sticky 9 Stafford, E. M. Control of scale insect pests of olives in the Sacramento and San Joaquin valleys. 3 p. Univ. of California Agricultural Experiment Station, Berkeley, Calif. (Litho- printed.) 1945. 32 California Agricultural Extension Circular 135 liquid and the fungus cause much difficulty in the harvesting, handling, and processing of the fruit. In some sections black scale is being partly or com- pletely controlled by the parasite Metaphycus helvolus. Tent fumigation using hydrogen cyanide gas in fall and winter gives good control but on large trees it is an expensive operation and the treatment should be applied only by experienced and licensed operators. Calcium cyanide dust may also be applied in the orchard without the use of tents. Here again the application of such a nj ^' O H Fig. 16. — Oleander scale (Aspidiotus hederae) on olives. deadly poison must be done only by experienced persons. Oil sprays are the standard remedy for black scale, the amount of control depending almost entirely on how well the spraying is done. Thorough coverage of trunk, limbs, and foliage is essential. From 10 to 60 gallons of spray material per tree will be required. The spray is applied in late summer after the eggs have hatched. A summer oil of light-medium grade is recommended, used at the rate of 1% to 2 gallons per 100 gallons of water. Promising results have been secured experimentally in the control of black scale by winter spray of light-medium oil containing 5 per cent DDT at 2 gallons per 100 gallons of dilution. Oleander Scale. The oleander scale, Aspidiotus hederae (fig. 16) , is armored and has a yellow body underneath a whitish covering. It often appears in greatest numbers on the leaves but seldom seriously weakens the tree. When fruits become infested, that part of the olive beneath and around each scale is delayed in maturing; the result is that green spots persist as the olive takes Olive Culture in California 33 on its normal dark color. Infested fruits may also become pitted or deformed and unfit for pickling. They are also deficient in oil content. Olive, or Parlatoria Scale. The female olive scale, Parlatoria oleae (fig. 17) , has a gray covering with a black spot at one side of the center ; the covering is less circular than that of the oleander scale. It may become so abundant on branches that the scales overlap. Infestation of fruit causes dark-purple spots Fig. 17. — Olive, or parlatoria scale (Parlatoria oleae) on olives. to form on the green surface. The oil content of olives may be reduced from 20 to 25 per cent by heavy infestations of either oleander or olive scale. Control of olive and oleander scales is accomplished by means of tent fumi- gation with heavy dosages (100 to 110 per cent schedule) of hydrogen cyanide gas (see warning under "Black Scale") or by oil sprays. These two armored scales are more difficult to kill than black scale ; therefore, a thorough job of spraying is necessary. Oil spray injury sometimes occurs; but satisfactory pickles, both green and dark, have been made from oil-sprayed olives. Olive Leaf Mite. A species of eriophid mite, Oxypleurites maxwelli, was found on olive leaves in Sacramento and in Ventura County in 1938. Since that time, it has been found widely distributed on olive trees in California and 34 California Agricultural Extension Circular 135 probably occurs wherever they are grown in this state. The mite feeds on terminal buds, in blossoms, and on upper leaf surfaces and breeds most vigor- ously on young, tender leaves. When new leaf production ceases and the leaves harden, the mite population drops to a minimum. The mite remains on the leaves the year round, but so far as observations indicate, it causes no leaf damage or other injury. Individual mites cannot be seen without a lens mag- nifying 10 to 14 times. Twig Borer. The branch and twig borer, Polycaon confertus, 10 attacks the olive and many other fruit trees. Its work consists in boring small holes at the base of the bud or in the fork of a small branch. Injury occurs when the branch breaks off at the hole. Control measures are seldom if ever necessary. Bark Beetle. The olive bark beetle, Luperisinus calif ornieus, is a small beetle about % inch long which burrows into the bark of olive branches. It prefers sickly or declining trees but does not hesitate to attack healthy wood. The maintenance of olive trees in a thrifty condition generally precludes attack by the beetle. Pruning out and burning of infested branches should be practiced. Prompt burning of all pruning wood is important in order to eliminate possible breeding places for the beetle. Root Nematodes. The lesion nematode, Pratylenchus musicola, is very prevalent on olive roots in California. It apparently attacks only the bark portion of the root and does not kill the whole cambium nor cause a rotting of the roots. The work of this nematode is indicated by longitudinal, black cracks in the bark of larger roots. It is doubtful if this species seriously impairs the health and productiveness of olive trees. The olive is also a host of the root-knot or garden nematode, Heterodera marioni, especially in sandy soils. Young trees may be seriously weakened by attacks of this nematode. But when trees become well established, they can probably be kept in good production by proper cultural methods. There is no effective remedy for either of these nematodes. HANDLING THE CROP Olive growers usually deliver fruit promptly after picking to near-by proc- essing plants. In case the olives are processed in some distant plant, hauling is usually done by the buyer. Facilities are seldom available for pickling the entire crop immediately, and olives are therefore commonly stored in a hold- ing solution. A salt brine of 30° to 32° salinometer reading is a satisfactory solution for most varieties. Holding solutions are used for two purposes : storage for a short period of time to obtain uniform lye penetration in the pickling process and subse- quently better color, and storage for a prolonged period as a matter of business expediency. Prolonged storage in brine needs careful attention to prevent spoilage and consequent loss of fruit. Olives are graded in the processing plant according to size. The unit of measurement is the shortest diameter of fruit in sixteenths of an inch. Olive sizes below 10 / 1Q inch are generally used for oil pressing. The California 10 Essig, E. O. The olive insects of California. California Agr. Exp. Sta. Bui. 283:52. 1917. (Out of print.) Olive Culture in California 35 Agricultural Code specifies that canned ripe olives shall show the following average counts per pound: Small to standard, 135; medium, 113; large, 98; extra large, 82; mammoth, 70; giant, 53-60; jumbo, 46-50; colossal, 36-40; super-colossal not over 32. Actual sizes of olives are shown in figure 18. Average grades of olives pro- duced on over 600 acres of olives in Tulare County in 1941 are given in table 4. During recent years a market has been developed for fresh green olives in the eastern United States. Barouni and small-sized Sevillano are the varieties TABLE 4 Average Grades of Olives in Tulare County, 1941 Grades Mission Manzanillo Ascolano and Sevillano per cent 13 7.3 24.4 21.0 16.9 18.4 10.7 per cent 0.9 7.7 17.6 20.5 18.7 22.0 12.6 per cent 23.5 24.7 Giant 21.0 11.5 2.1 0.5 Culls 16.6 Used for oil 56.7 6.0 1.5 mostly used. The fruit must be green so that it will arrive on the market with a straw color. The olives are graded for size and shipped in lug boxes in refrigerator cars. Commercial pickling of olives and extraction of oil require special equip- ment and extensive floor space. The Division of Food Technology, University of California, Berkeley, has done an immense amount of work on olive prod- ucts and can supply detailed information on their preparation. A publication 11 is available for those who may want to pickle, can, or cure olives in the home. ECONOMIC FACTORS Prices paid for olives increase appreciably as fruit sizes increase. For example, average prices per ton paid to growers for Mission and Manzanillo olives for the nine crop years 1921 to 1929 were as follows : mammoth, $201; extra large, $154 ; large, $103 ; medium, $63 ; small and oil, $38. Sevillano olives have brought much higher prices than have Mission and Manzanillo. Average Sevillano prices for the same period were : colossal, $363 ; jumbo, $208 ; giant, $96. For comparative returns per acre for the different varieties, total production per acre and percentages of the different sizes must be taken into account. Abnormal prices for olives due to war conditions should not be used in figuring possible future returns. 11 Cruess, W. V., and Eeese H. Vaughn. The home pickling of olives. 7 p. California Agri- cultural Experiment Station, Berkeley. (Lithoprinted.) 1945. 36 California Agricultural Extension Circular 135 California olives are processed and marketed mostly by independent con- cerns. Some growers have formed cooperatives to process and market the olives produced by members. Such cooperatives handle 40 per cent of the crop in some districts. An organization known as the California Olive Association with headquarters in San Francisco is a trade association of ripe-olive can- ners organized for the purpose of promoting the interests of the ripe-olive canning industry; it is not a cooperative marketing association, but serves as a clearinghouse on matters affecting the entire industry. "Small" "Select" 'Standard (s)" "Medium" "Large" 'Ex. Large" ■Mnmmotli 'Giant" "Jumbo" 'Colossal" 'Super-Colossal' 53-60 46-50 36-40 Maximum 32 Fig. 18. — Eipe olive sizes and grade names. Figures give average number of fruits per pound. 8|m-5,'47(A2870)