JOHN H. MacGILLIVRAY A. E. MICHELBACHER C. EMLEN SCOTT TOMATO PRODUCTION IN CALIFORNIA THIS CIRCULAR G IVES YOU INFORMATION ON: c all phases of tomato production — economic aspects, varieties, seed, field seeding, trans- planting, irrigation, staking and pruning, harvesting and handling. tomato diseases— their symptoms, prevention and control. insects attacking tomatoes— how to recognize and control them. CIRCULAR 167 JUNE • 1950 California Agricultural Extension Service The College of Agriculture University of California • Berkeley ERRATUM The caption for Figure 30 belongs with Figure 31. The caption for Figure 31 belongs with Figure 30. THE AUTHORS: Mr. MacGillivray is Professor of Truck Crops and Olericulturist in the Experiment Station, Davis. Mr. Michelbacher is Assistant Professor of Entomology and Associate Entomologist in the Experiment Station, Berkeley. , Mr. Scott is Agriculturist in Agricultural Extension, Berkeley. This publication supersedes Extension Circular 104. TOMATO PRODUCTION IN CALIFORNIA John H. MacGillivray A. E. Michelbacher C. Emlen Scott California tomato growers have dem- onstrated their ability to increase acreage and yield per acre under the stimulus of war-time demand for food. During 1942- 1945, their somewhat higher production costs due to labor, irrigation, and distant markets were not factors of importance. Now, the grower needs to give considera- tion to the maintaining of high yields, reducing cost of production (particularly the abandoning of unproductive prac- tices), and producing a quality product which can compete in markets in eastern United States. Emphasis on picking will do much to provide a better quality to- mato for canning. Care in picking "green wraps" will insure more even ripening on eastern markets. Tomatoes which have been subject to low field temperatures will be affected by chilling injury with consequent impairment of quality. Ac- curate and skillful picking of tomatoes is not easy to accomplish, but skill in handling labor will probably return greater profit than will improvement in production practices. Many of the essen- tial points to consider in an adequate to- mato program are given in this circular. ECONOMIC ASPECTS OF THE TOMATO INDUSTRY The importance of the tomato among our various vegetable crops has increased markedly in the last 25 to 30 years. At present, tomatoes are next in value to white potatoes in the United States. Both the market and processing values of to- mato crops have increased, with pro- duction taking a decided upward trend during wartime. Tomatoes are most com- monly used as a fresh vegetable for salads and as a canned product alone or com- bined with other foods. Tomatoes for Fresh Market. — Table 1 shows the value of tomatoes in the country as a whole, and in some of the more important tomato producing states, for the period 1942-1949. In California, about one-seventh of the tomato crop is sold on the fresh market, and nearly one- half of that fresh-market crop is shipped out of the state. The remainder of the crop is used for processing. In the United States, the market crop was grown on almost 250,000 acres and had a value of 87 million dollars. About 20 per cent of the market crop was raised in California. Most of the California crop is picked in the pink or green stage and is shipped to terminal points where the fruit is rip- ened before marketing. Tomatoes har- vested at this stage are sometimes called "green wrap" when fully green and wrapped. Riper fruits are sold locally. Table 2 shows that tomatoes are har- vested and marketed in California during every month in the year, with the smallest production in March. June to November, inclusive, is the greatest period of pro- duction for market, with most of the east- ern shipments made during October and November. In the eastern markets, the leading states shipping to New York City and Chicago seem to have little overlap in their period of shipment. At New York City, Florida supplies the market from December to May, Texas from May to August, New Jersey from July to Sep- tember, and California during October and November. Texas and California supply the December market. [3 TABLE 1 — Production Data for Fresh-market and Processing Tomatoes (Averages, 1942-1949) Acreage Yield per acre Production Price Farm value Fresh-market United States acres 248,199 33,156 29,663 84,013 10,875 9,231 bushels * 121.5 182.1 134.3 72.4 162.9 209.7 bushels 30,151,125 6,038,250 3,982,875 6,086,625 1,771,250 1,936,250 dollars 2.90 3.64 5.24 2.39 2.46 1.74 thousand dollars 87,408 22,002 20,876 14,563 4,355 3,366 California Florida Texas New Jersey New York Processing United States acres 514,240 115,305 95,675 33,488 48,688 28,525 27,538 tons 5.79 8.88 5.03 6.15 4.47 5.54 6.67 tons 2,979,963 1,024,075 481,413 205,938 217,850 158,013 183,813 dollars 26.58 25.91 24.25 32.60 30.60 29.05 23.41 thousand dollars 79,194 26,531 11,675 6,712 6,665 4,590 4,303 California Indiana New Jersey Maryland . . Pennsylvania Ohio Source: Agricultural Statistics for years 1944-1947. U. S. Department of Agriculture, Washington, D.C., and similar sources. * 1 bushel = 53 pounds. Tomatoes for Manufacture. — About 85 per cent of California toma- toes are used for canning. The California average for 1942-1949 was about a mil- lion tons, grown on about 115 thousand acres. The price received per ton was higher than that in either Indiana or Ohio, but lower than in states farther east. The following data on California's output of the canned product are for the years 1947-1949. The total pack was 26,129,745 cases of various sized cans, divided as follows: tomato juice, 22.9 per cent; catsup, 19.4 per cent; canned tomatoes, 18.6 per cent; tomato paste, 15.6 per cent; sauce, 14.8 per cent; puree, 6.1 per cent; chili sauce, 2.0 per cent; and miscellaneous, 0.6 per cent. During the war, there was a large in- crease in the production of processed [4 tomatoes in California in spite of the long distance from large consuming markets, the problem of worm control, and, to a lesser extent, the damage from molds and rots. The weekly receipts of canning toma- toes show that the major portion of the crop is harvested during the last part of September and most of October (fig. 1). The weekly receipts of over 75,000 tons are shown below (1942-1949) : Tons September 14-September 20 82,349 September 21-September 27 115,742 September 28-October 4 135,855 October 5-October 11 143,218 October 12-October 18 132,262 October 19-October 25 120,998 October 26-November 1 96,845 ] tJ< N CD Tl t lO^OP 1 > l> IO rH CO CO tN ** ci js o o) oo if > H 00 W r O O ^ ^ rH rH tN CO rH O O t> »0 00 t- CO IO rH Q o t> to a> a ) i H rH iH rH y-i rH a o to 3 t- O N N ^ Hr tN « io io os oo CD CC O rH rH CO IO IO if i ^_ P iH (N y-i O 3 > CO O CO C> 1 SS N « > IO • 00 »0 ■"# t~ tN r^ d o oo t- -* tN • tN O "«* y-i r- .2 55 CO iH tN • rH rH ir > a o *• t> • rH O • O 00 CC > fl E O rH Tj IO t 00 • CO rH • O CO CN • rH • tN CC cc 1 2 J 1 © J* c« ^ . . CO CT > • i-l CN tN • rH IO • C- rH CC O » • • c- a I • « CO CO • rH tN • t- IO M 2 D hi • • CO r- • "tf CO • rH CN IO • CO CO rH tN CO Cs 0) s In 0» 3 • • tH C 00 • IO »tf rH c ^ » y-i y-i O IC rH t* CO ^ tN OJ Tji y-i IO CN CO a • c > "■' "3 CO 00 tH r- CN C5 T- w O t •-9 rH 03 rH T* r- M 1- 0* © v O «*h CO o a. O (4 ree Mark ing Areas • a 5 o t> t> CO t^ u CO "* t» IC o H CO O) CO • a 1 1 a 5 § 1 Xi 1 rH CO 0) O IO rH rH CD rH IO CO Tj» tN c t> t» rH IO rH rH CO rH OC fc • CO rH • t> tt M e "3 -c a 2 | C- O t> rH t> • O CO c bo M CO "^ | CN 1 CO • CO cc 3 CO o "cd J TB C -3 05 Tj< • * rIN rl K 5? • rH • • CN T- "2 P. o rH O • CO • O .9 CN CC jj • rH • • 00 • rH • rH r- * rhly Unl m Impor a> S5 O CO bo H • t> • rH • • CN J . f- . . T}1 b- i . CO • CN • • ■ Oi . IO . . CO • • rH • IT. c o 1 * o • t> • rH rH • l> rH rH rH O o: ■a o • IO • • IC IO • 00 ir; >« o fa • T-4 y-t r- > 0) o ft. Ss > CO CO • *h r~t en O CO rH -^ CO t- • or CO n t> • • cr tN 0> rH 00 CC o 1 •-9 rH ri 5 « bo eg UI CO > -1 >» •o 03 < g CO 3 1- > .J S I J3 c 'So e8 CD GO o3 o 73 (9 o ^ * 03 *j CM o ee a> o > fi TJ Eh 5 ea o s o 4 i CD 03 1 o > Jh 1 > a ► CO C 1 cr "S | eX 1 o O "§.9 cl 3 o _ a* i* J o ! xa M * 2 09 c § I O 03 • 1-1 £ O «*h if Eh fc O 55 H O S Cm •J »q w w & m & 1.000 TONS 14 21 SEPTEMBER 12 19 OCTOBER Fig. 1. Weekly receipts of canning tomatoes in California (average 1942-1949). The last date of each week has been used to record data. (Source: mimeographed report of State Department of Agriculture and U. S. Department of Agriculture.) PRODUCING DISTRICTS Table 3 shows the average 1942-1948 acreage of market and canning tomatoes by counties, for early spring, early sum- mer, and fall. The groupings for truck crops for fresh market were adopted in 1943 by the United States Department of Agriculture, and correspond to the sea- sons of the year. Each group in table 3 shows the period when the heaviest sup- plies of the crop are available. Thus the term "early spring" refers to a peak mar- keting period during April and the first half of May, "early summer," to the month of July and the first half of August, and "fall," to the period from October to December. TEMPERATURE REQUIREMENTS Since the tomato is a warm-season crop, a long growing season is essential— at least 7 months for field seeding and 6 months for the transplanted crop. These months must be frost-free or the crop must receive some protection, as it is sen- sitive to frost. Tomatoes produce best with average monthly temperatures of 70° to 75° F, but are grown commer- cially as low as 65° to 70° F and as high as 75° to 80° F. The crop is poorly adapted to average monthly temperatures above 80° F, and fruit is damaged at tem- peratures near 30° F. Tomatoes are sub- ject to chilling below 50° F, with actual chilling injury at or near 40° F. Such fruits do not show any indication of in- jury at the time of picking but are fre- quently responsible for losses at terminal markets due to erratic ripening and rots. The plants may be barren if the flowers open for pollination when the tempera- [6] oH HO 00 2 I cn c o > o 0) c 00 CO 5 i-H co CO o T-i CO CO CM -<* eo O V s S U3 t> lO o Oi < § a .3 2 e3 e3 § WWCQt 3 CD w a CD c* C/2 M S S CD e3 o o ■"5 G CD CC? c o E E o u V IO M t-H O 00 eo "* Q 00 00 IO CO 00 ^ _J* t> o ^ o 00 M CT> 00 l> o «* Tj< iH t- P< tH 00 Tjl ^ *! °1 o °i lH ta of ** tN "O IO of CM cm j: r-T CN 1 tH o 3 fc N V s-^ ^.^ ^^ 73 13 , — s T3 ■"# CD co T3 CO '■3 bo ■B a, X o CM ^3 X -1 CO x^ X CO ■a -** CO M >H e« g ^ Th e3 fa- CO 03 '3 e9 CO CO 2 ■a o > 1 CO CO M O CO § § e ca s g> O el) CO § CO c3 cs cu c3 N (-i o3 00 S 2 c3 CO CD £8 § CO fa CO «8 o3 O cu c3 |5 CO iH CO •J3 CO § CO 3 13 1 of i o o CO CO 5 U CO o CO c3 CD .£ fa fa CO *c o3 » CD i—i H o3 fa > cfl » H < s .s-s O.'o CO c3 CO > Jz; CO w fa c3 n3 e3 d, CO CO s § co 6 1 o3 5 fa 5 fa a. cd 3 w CO 1 * o CO ►J fa fa VARIETIES The grower chooses his tomato varie- ties on the basis of their future use (can- ning or fresh market) , yield, color, fruit setting at various temperatures, shape (for packing), and disease resistance. New varieties are constantly being tested by the University, by seed companies, and by the growers themselves, with spe- cial interest in disease-resistant strains. It is to the grower's advantage to make small field trials of new varieties, since by so doing he may improve the market value of his crop. The following list includes brief de- scriptions of the most important com- mercial varieties in California. Table 4 gives the common planting distances. Earlicma types: Several improved strains are now available. The types most generally used are: First Early; Morse's 498; Early Market; and Pennheart. Plants are smaller than late canning varieties, and require only about one- third as much space per plant. Fruits are red, early maturing, smooth, and globu- lar (fig. 2 A and B) . They are smaller than those of late varieties. Use: Fresh market. Mainly for extra- early, spring shipments from Imperial Valley and similar desert areas where growers cater to a local market. Early Market: See Earliana. Early Santa Clara: Grows vigorously and forms large plants. Fruits are large, flat, uniform in size, but slightly rough (fig. 3), with many seed cells. Use: To a very limited extent, for can- ning, in the northern part of the state. First Early: See Earliana. Morse's 498: See Earliana. 1 33-8: Grows vigorously. Dense foliage protects the fruits which are large, scar- let, firm, and semiglobular. (Similar to 133-6, but larger, and with later fruits.) Pearson: Most commonly used variety in California. Has grown in popularity because it sets fruit over a wide range of temperature. The intervals between pickings for the cannery may be longer with a heavier harvest at each picking. Plants are compact, medium-sized, with some concentration of fruit set. Fruits are medium-sized, with flattened globe, thick skin, and average color (fig. 4). Fig. 3. A typical fruit of the Early Santa Clara canner. [ii] Use: Forms a large percentage of the canning crop. Is also popular as a fresh- market variety. Pennheart: Developed from a cross of Oxheart and Penn State Earliana. Plant is medium small and "self-topping" (fig. 6). Produces a heavy, early crop. Fruits are globular, scarlet, about three to a pound. Use: Early fresh-market crop in Imperial and San Joaquin valleys. Protchard: Introduced by the U.S.D.A., and formerly called Scarlet Topper. Plants are medium-sized and self-top- ping. Fruits are nearly globular, thick- meated, with good color. Use: In the Merced area, for staked to- matoes, and as a local fresh-market crop. San Marzano: Also called Italian Pear or, sometimes, just Pear, because of its shape. Plants are medium-sized and somewhat open. Fruits are two-celled, grow in numerous clusters, and are small— 3% inches long, 1% inches wide (fig. 7) . Flesh is mild in flavor, with little juice. Color is deep red. Fruits of this variety have tough skins, and will remain on the vine for a long period. Thus, less frequent picking is necessary. The final picking is usually made by cutting the vines at the soil surface and, a few days later, shaking the fruits off. Picking up the tomatoes from the ground is faster than picking them off the vines. Use: Primarily in the making of canned tomato paste, because it gives a product of thick consistency. Has been used for solid-pack tomatoes to a minor extent. Stone (Norton) : Plants medium-sized, with heavy foliage. Fruits are medium to large, with flattened globes, and about 6 ounces in weight. Color is deep red. The Norton strain is partially resistant to Fusarium wilt. Use: Grown mainly in the southern part of the state, for shipping and canning. Fig. 4. Some typical fruits of the Pearson, an important canning variety. 12] Fig. 5. The stem tip of an indeterminate plant (left) shows that in such plants, the stem continues to grow longer. In the determinate (self-topping) plant at right, growth has stopped with the forma- tion of a fruit cluster, a characteristic of Pearson, Pritchard, and Pennheart varieties. Fig. 6. A determinate plant of the Pennheart variety. [13 PRODUCTION INPUTS AND COSTS 1 Labor and material used, and produc- tion costs for tomatoes vary widely in the different areas of the state, and from farm to farm within those areas. The Agricultural Extension Service conducted studies and surveys on inputs and costs in several counties. Their findings for two areas have been summarized, and ad- justed to current wage conditions, in the two sample schedules of costs shown in tables 5 and 6. These examples would apply to pro- duction areas of better-than-average con- ditions, where yields are better than the state average (10 tons per acre in 1947 and 1948). Hours of labor and hourly rates at which labor costs were figured are given so that the grower may adjust them when figuring costs for his own farm. Table 5 is an example of inputs and costs for the Yolo-San Joaquin counties area, where many of the canning toma- toes are produced. A yield of 14 tons per acre is assumed— an amount usually reached or exceeded by the majority of growers in that region. Costs are shown as for an owner-operator. Table 6 is an example of inputs and costs for producing staked tomatoes for shipping, in Merced County. Costs are figured on the basis of cash rental for land, a common practice in that district. The yield shown— eight hundred 30- pound packed boxes per acre of shipping fruit, and 8 tons of canning fruit— is ap- proximately what successful growers ex- pect under favorable conditions. It is, however, considerably above the average for the district as a whole. Income from the 8 tons of cannery tomatoes is deducted from total costs to obtain the net cost of producing the shipping tomatoes. The net figure represents costs delivered to the packing shed. Packing costs, boxes, loading, etc., in 1947 and 1948, were about 80 cents to $1 per box. 1 The data on costs and inputs (tables 5 and 6) were prepared by Arthur Shultis, Agricul- turist in Agricultural Extension and Associate on the Giannini Foundation, Berkeley, and B. B. Burlingame, Associate Agriculturist in Agricul- tural Extension and Associate on the Giannini Foundation, Berkeley. Fig. 7. A vine and box of San Marzano tomatoes. [14] TABLE 5 — An Example of Inputs and Costs for Canning Tomatoes with a Yield of 1 4 Tons per Acre, Stockton to Woodland Area (transplanted, 3' x 6', 2,400 plants per acre) Hours per acre man labor tractor truck Costs — dollars per acre per ton Growing plants Land preparation Transplanting and replanting Hoeing and weeding Irrigation, 4 or 5 times Cultivation and furrowing, 5 times Fertilizing Pest and disease control Miscellaneous 10 4 5 6 12 4 1 2 2 .1 4.0 1.0 4.0 .5 .5 .5 .1 i.o 8.77 11.40 6.95 5.10 10.20 8.20 1.60 2.45 2.45 Subtotal cultural labor Picking, 602 boxes (usually piece rate at 17 cents) Hauling boxes and fruit including loading. 46 150 15 10.6 1.4 5.0 57.12 127.50 20.25 Total labor cost . 211 10.6 6.4 204.87 Irrigation water 24 to 30 acre-inches Seed and coldframe supplies (1 oz.) Fertilizers, commercial 400 lbs. at $60 per ton. Pest and disease control materials Miscellaneous materials 7.00 2.00 12.00 9.00 2.00 4.08 9.10 1.45 14.63 Total material costs 32.00 2.29 General expense County taxes on land Repairs to equipment. . . . Compensation insurance . 11.84 6.60 2.00 2.00 Total cash overhead costs 22.44 Investment overhead based on 100 acres in farm unit General farm buildings Irrigation system Tillage equipment Coldframes Transplanting equipment Miscellaneous other equipment Land Total investment Total depreciation Total interest on investment Total all costs Original cost Average value Interest at 5% Depre- ciation Dollars per acre 12.00 40.00 10.00 10.00 6.00 5.00 500.00 583.00 6.00 20.00 5.00 5.00 3.00 2.50 500.00 541.50 .30 1.00 .25 .25 .15 .13 25.00 27.08 .30 2.00 1.00 2.00 .60 .50 6.40 6.40 27.08 1.60 .46 1.93 292.79 20.91 Labor costs above are based on the following hourly rates: man labor, 85 cents; tractor for land prepa- ration, $2; cultivating tractor, $1.20; truck, $1.50. The cost of growing plants, as included above, amounts to about $14 an acre with pulling included in transplanting around $5 per 1,000. If yield were only 10 tons but all costs except harvesting were the same, cost per ton would be about $25. ■o o c o ec c o ■b © ID 8 CD 8*g .2 » £ < "8 u o a- CO s o c "8 C c o 3 U £ o C w) 3 C o o u i- -o co fl — a d a .Ex a c> o 2 c M "S u .* O Q- v a £ 8 CO £ ° o o ■- CO © o ■82 M- >• 8 3 5 C "8 o c A3 a E 8 o \a io o o o lO O iH io (N oo O 00 o o o O N fl) M o OOHHlOOOtOIOffi^NW 00 o o o o CO O CO O 00 W 00 ^ CD CO CD CO (N 38 ^ i-H 00 c- §888 CD ^i C> OS CO iH iH 8 35 o :::::: o c4 • c£ Is lO CM id co 5° o o o II qioooqqqqq doaiooddcoN 00 H W 00 ffllO H o q C* t-4 oq q id © as oo co bo •g a> o to T3 bo fl 1 if 31 O Ph PL, in pL, § § bo^ .§ fl bO B *3 .3 s-g-S §1 1 •rt o3 .5 bO ts > s» fl bo 43 o3 '>» *C fl ft Eh £ O BQ § '43 o3 > O 1» o bo ■fll fl bo 13 !» « 10 v -^ O W s g .5 «« N Jfl a> o co s g to "^ rfl a> bo fl S ft -a .— ■ ft * .& o 2 +» to •g L 00 « t, ► ft e3 o» "? to §1-1 fl c3 +* « o o3 fl 5m fl .fl 0) 23^ .2.2 i«2 Ph Ph W S q oq oo CO is bo to tO M o> o ^ -° 2 o3 fl bo fl to CO (1) *-i < s w "S "^ •fl o •3 S o fl *H sl fl « o v •43 .S o3 ^} .1 »-. o> he* rfl o be o3 CD 73 "^ cl § 3 1 ft- 2 lO O Q Q Q C> e4 CO 38 tA id 28 id d o cn * >» O OutfuO © w O O O IO IOOOH a* ■**■** t! ^' W H pi 3S88 t> o io «0 s co 9 > o fax 03 R CO o M eS u G o3 c3 M O o3 03 "a: «d V o ■a 13 0) Si o3 cfl 03 03 cf -** (A 8 0) i. < c ». 10 <* a) 1 § "co i •0 § to to •6 co £ O r co M d CO O u cfl r a3 o CO "cS bl C < CO > a> > "el "C a> p 2 >* S • R J • o3 03 co CM rH O O rH ) *o ' 0) T3 «) a> 01 o o o *H o O 1 4) 4- ID a> > O hJ fe O J a> 1 o co 03 • 9 < CJ p d co P d o3 »"8 > > X! 0] D) c3 O. c u a. 01 Is a) o Q c3 S bi < > 1 1 co ' 1 4* o O > o o d CO P +^» +i ft R CO CO 03 03 a) 0] • s 01 ■Z 0) 1-1 V 01 01 a, c •73 ® bib p, > R CD O ft sj co R c3 O ) i < •-a ^eg » 0> 01 Ul „ o3 2 -1 cG bo d xi g "3 cfl < I Pi 2 S > O 8 t 1 0) 2 >» r > £ i2 ft 5J & 1 *> 0) 53 Ol 0) O 13 1 ! fc fc fo § •-8 <3 IJ < 13 0) 1 & M > M O (8 u < < w as .5 * ft ts 03 a >» a; H .g o3 03 En £ 03 o3 o3 cc 5 5 s Sz; § 03 bo a S 1 | (figs. 18, 19, 20) may be made when con- venient, but the soil should be filled with available water to a depth of 6 feet just before the first harvest or before the main harvest. There should be little need for irrigation during the picking period. With a preharvest irrigation, the soil will have 8 to 12 inches of available water in the root zone. A soil tube or an auger are desirable for examining the deeper soils for moisture. After a grower has become familiar with a field and its soil types, the wetness of a soil may be roughly estimated by appearance and feel. A wet soil is dark in color and tends to hold together when squeezed in the hand. When tomatoes touch soil that is wet from irrigation water, there will be serious losses from rot. Tomatoes turning red are most likely to be affected. Tests in the central valleys indicate that canning tomatoes use the following amounts of water for the months listed: June, 3.2 inches; July, 4.5 inches; Au- gust, 7.0 inches; September, 5.2 inches; and October, 4.1 inches— a total of 24 inches. The following amounts of irriga- tion water are recommended for areas where the soil is filled to field capacity from winter rains or a preirrigation : coastal areas, 10 to 12 inches; interior valleys, including desert areas, 18 to 24 inches. 1 Staked tomatoes present a larger leaf area as a result of close planting, and would require somewhat more water. Where tomatoes root deep and thus have a large volume of soil from which to obtain water, there is little likelihood of sudden fluctuations of moisture in the plant with average irrigation. Therefore, there is little evidence to prove, under these conditions, that irrigation causes blossom drop or blossom-end rot in seri- ous amounts. Cultivation is primarily for the pur- pose of killing weeds which waste both soil moisture and soil nutrients. Weeds may be cut by shallow cultivating tools with little disturbance to the tomato roots. Time and frequency of cultivation de- pend upon the number of weeds to be controlled. STAKING AND PRUNING The tomato plant first forms a primary, semi-erect stem, then develops secondary stems from the buds in the axils of the leaves. Without pruning, the common tomato forms a prostrate bush shape, having several stems. Under the special form of culture known as staking and pruning, the side shoots, or most of them, are removed as they appear. They should be pulled out of the axils of the leaves, not pinched with the fingernail or cut with a knife. Pinching or cutting is likely to spread virus diseases, such as mosaic. Such diseases cause decreased yields in proportion to the earliness of infection. By pruning, the growth is limited to the main or central stem, which is kept erect by tying it at intervals to stakes or to wires stretched between stakes. Tomatoes grown under this method of culture are referred to by growers as "stick" or staked tomatoes (figs. 21, 22). The fruit cluster forms on one side of the stem, and the plant should be tied so that the clusters will not be against the stake, to prevent fruit injury. If a variety that has a small plant is selected, it may be desir- able to have two main stems so that the foliage will better protect the fruit against sunburn. Sometimes two stems will also increase yields, particularly if wider spac- ing is used. There is some evidence that pruning and training to only one stem cause decreased yields. Plants to be staked and pruned may be spaced 12 to 18 inches apart, and sometimes are planted as close as 9 inches, with rows 3 to 4 feet apart. This arrangement gives three or more times as many plants per acre as does an early variety grown without stak- ing and pruning. Staking and pruning 3 Doneen, L. D., and John H. MacGillivray. Suggestions for irrigating commercial truck crops. Calif. Agr. Exp. Sta. Litho. 1943. [29] Fig. 18. Tractor making an irrigation furrow in to- mato field. Fig. 19. On many soils, well-filled furrows will in- crease lateral penetration of water and insure wet- ting of all soil between rows. Fig. 20. Irrigating to- mato field by use of siphon to draw water from head ditch. Siphons are light in weight and easily moved. Pipes, air hoses, or other devices are also placed through banks for the same purpose. experiments indicate that this practice results in more plants per acre and a greater production of early fruits per acre. Fruits kept off the ground may be of better quality and are easier to pick. Staking procedure involves higher costs of production per acre for labor, plants, and materials. Growing staked tomatoes is a specialized procedure and is used in Merced for shipping and in other areas where the fruit is sold on near-by or local markets. UNSATISFACTORY FRUIT SETTING Pollination, fruit setting, and tomato yields are closely related. The fruit is de- veloped at the expense of food manufac- tured by the plant foliage; therefore, it is of primary importance to produce a large plant which will have many blos- soms. Adequate soil nutrients or fertilizer constituents, irrigation, and other envi- ronmental factors all affect plant growth, number of fruits and their size, and, con- sequently, yields. There is also evidence that temperatures are an important fac- tor where blossoms fall from the plant without forming a fruit. Failure of the pollen to germinate, thus affecting fruit- set, may be influenced by high or low temperatures. Night temperatures below 55° F for several hours, or day tempera- tures of 100° F, tend to prevent fruit setting; 70° to 80° F is more favorable. There has been considerable publicity recently about the use of hormone sprays to set tomato fruits. 4 Several compounds have been used, but sodium para-chloro- phenoxyacetate seems as reliable as any when used at a concentration of 50 parts per million. Hormone treatments in gen- eral have proved effective in setting fruit on plants grown for early-market toma- toes when weather conditions were un- favorable for natural setting. However, work on hormone sprays for setting to- matoes is still in the experimental stage. Recommendations for general field spray- ing cannot be made at present. Spraying tomato plants with hormones may be dan- gerous. Some trials have shown serious injury to foliage and some to fruit. HARVESTING AND HANDLING Tomatoes are picked in several stages of maturity, depending upon how they are to be marketed. As a fruit matures, there are changes in its color, texture, and taste. Fresh-market Crop. — After the fruit forms, it makes most of its growth as a green fruit. After maximum size has been obtained, there are changes in the color and feel of the fruit. Picking at the ma- ture green stage is not an easy matter, and the grower should look for the fol- lowing characteristics of mature green fruit: (1) maximum size for the variety; (2) development of a corky stem scar; (3) on an immature fruit, the skin can be rubbed off, but this is not true of a mature green; and (4) when a mature green fruit is cut with a sharp knife, the seeds are hard enough not to be cut. The next stage is "breaker," or the first col- oration around the blossom end. This is followed by the so-called "pink" stage and then the fully red stage when the fruit is entirely ripe. As the fruit ripens, it becomes more soft in texture and the pulp around the seeds becomes gelatinous in consistency. The green wraps and some pinks are used for shipment to dis- tant markets. Local markets use both the pinks and fruits which are almost ripe. The canning industry prefers the ripe, fully red tomatoes. Rate of ripening and color develop- ment are affected by temperature. Tem- peratures may be so high that the 4 Further information may be obtained by a request to the Truck Crops Division, Davis. [31] development of the red pigment is re- tarded or prevented. Average daily tem- peratures of 65° to 80° F are thought to produce the best color, but the air tem- peratures may be higher if the fruits ripen in the shade of the leaves. Shipping tomatoes are sometimes chilled in the field due to low fall temperatures, such as 40° to 45° F. This does not affect the appearance of mature greens at pick- ing, but may cause serious losses from decay during transit and ripening. The exposure of the fruits to low tempera- tures in the field may make the tomatoes more subject to harmful effects from low temperatures after they have been har- vested. Green Wraps. — These fruits for the fall crop are usually planted to reach picking stage near the latter part of Sep- tember. The fields are picked at least once each week and sometimes the riper toma- toes are sold to local markets or canners. After the fruits arrive at the packing house, they are washed, waxed, and sized. They are wrapped in paper and packed in Los Angeles lug boxes with a net weight of at least 30 pounds. Three layers of fruit are packed in these lugs, and the size of the fruit is designated by the num- ber of fruits in the top layer. For example, a top layer having five rows of tomatoes extending crosswise and six rows extend- ing lengthwise would be designated as a ; * :. r - lIC Fig. 21. Left: Staked tomatoes. Note the stake by each plant, and wire support. The plants are closely spaced. Fig. 22. Right: Imperial Valley staked tomatoes which were started with protection by brush and by paper caps. Large stakes were used earlier for supporting brush. 32 f J^ Fig. 23. Packing green-wrap tomatoes in grower's packing house. Each box contains four baskets. packed in 3-quart with four baskets 5x6 pack. The Merced early summer pack of tomatoes is usually 6 x 6 or smaller, while the fall packs of other areas are 6 x 6 or larger. The Imperial and early spring crop is till baskets (fig. 23) per crate. Ripening. — Fruit picked mature green ripens and colors up within one to three weeks, according to storage tem- perature and the degree of maturity when picked. Upon reaching market, the fruits are unwrapped; those showing sufficient color are sold at once, and fruit still green or only partly colored are placed in spe- cial ripening rooms. In gathering mature green tomatoes, careless pickers take some that are not mature. These are a distinct disadvantage, as they increase the unevenness of ripening, and some tomatoes may even be a total loss. Toma- toes picked in the turning stage, when they show a little pink at the blossom end, are of more uniformly high quality when artificially ripened than are those picked green. The storage period is also shorter for fruits picked at this slightly pink stage. Temperatures of 55° and 75° F are the extremes for ripening. A temperature range of 65° to 70° F favors good color development. A range of 70° to 75° F will give most rapid ripening. The maxi- mum storage life of tomatoes is obtained with a temperature of 55° F. They can be held for not more than three weeks at this temperature and, upon removal to a temperature of 70° F, will attain ripeness in another week. If stored at less than 50° F for more than a few days, the fruit may not develop good color or flavor when removed to higher temperatures and may even decay before reaching an edible con- dition. Prolonged cold storage of either green or ripe tomatoes is therefore not recommended. Ripening of the immature fruits in storage can be accelerated by adding small amounts of ethylene gas to the air. A concentration of 1 part ethylene to 2,000 to 4,000 parts of air seems ade- [33] quate. Though explosive in mixtures of 1 to 3 with air, the gas is not dangerous at these recommended low concentra- tions. Use of ethylene will reduce by four to seven days the time required to ripen tomatoes. The gas is obtained, in com- pressed form, in steel cylinders from which the measured amount is discharged into the ripening room each day. The room must be approximately airtight to prevent too rapid a loss of the gas. As oxygen is also essential for normal ripen- ing, fresh air should be admitted each day. Favorable temperatures must be maintained in the ripening room even when ethylene is used. Canning Tomatoes. — The process- ing industry desires fruits of good color. Tomatoes are graded, and must meet the specifications for the canning grade in the State Agricultural Code. The fruits are usually picked directly into 50-pound lug boxes, but sometimes pails or similar containers are used for carrying them to the boxes. Proper supervision of the pickers so that the loads will comply with the state canning grade is important from the standpoint of income. Indiscriminate picking of tomatoes causes the inspectors to reject loads which must then be re- sorted or discarded at considerable finan- cial loss to the grower. YIELDS The yield depends upon fertile soil, a good plant stand, proper timing of cul- tural practices, length of harvesting sea- son, and prevention of damage by insects and diseases. Tomatoes produced for a spring shipping crop, as in the Imperial Valley, yield about 4 tons (or 250 lug boxes of 30 pounds each) of packed-out fruit to the acre. Other shipping areas produce slightly higher yields, or about 5 tons per acre. The tomatoes harvested in the fall in the southern part of the state produce the greatest yield for fresh ship- ment. Canning tomatoes, however, are much more productive. While the state average yield is 10 tons per acre, the grower's goal should be from 15 to 25 tons. PROBLEMS OF THE TOMATO GROWER California as a canning state has the advantages of high yields, better-than- average color, "low mold count" of to- mato products, and the opportunity, in periods of good prices, to can tomatoes after the crop has been killed in the East by frost. Damage to fruits by insects is a much more serious problem in the West, and tomato products with too high an "insect fragment count" may be seized and destroyed by the Federal Pure Food authorities. Our western tomatoes are low in active acidity and consequently our processing times must be longer than are those in the East. This causes breaking of the tomatoes in the can. Brokers and wholesale buyers of canned tomatoes want the fruits to come out of the can in a whole condition, and will pay a premium for this type of canned product. Whole canned tomatoes are spoken of as "solid pack," and for many years this type of pack has been small because all fruits were not suitable. Our advantages may be greater in the production of to- mato products, such as juice, puree, paste, catsup, chili sauce, etc., rather than canned tomatoes. Our fresh tomato shipments are mostly made in the fall to supply eastern mar- kets after local frosts and before the ar- rival of shipments from Florida and other southern states. Transportation losses are large on shipping tomatoes because of field chilling, difficulty of controlling re- frigerator car temperatures at around 60° to 70° F, and length of period in transit to market. [34] DISEASES OF TOMATOES Tomatoes in California are subject to many diseases, any one of which may cause considerable loss to the grower. This section discusses the principal dis- eases, describes their symptoms, and suggests controls and preventive meas- ures where feasible. Damping-off is caused by soil-inhab- iting fungi, including Pythium, Rhizoc- tonia, Sclerotinia, and Fusarium. The organisms enter the stems of young seed- lings at the soil surface, and destroy the stem tissue. This disease usually shows up in small areas, but spreads rapidly, and unless checked, may destroy the en- tire bed. Symptoms. — The first symptom is a slight drooping at the tips of the young leaves and a general loss of turgidity. Marked wilting soon develops, and the stems appear water-soaked at the soil sur- face. Diseased plants soon bend at the soil line and fall to the ground. If hu- midity is high, the weblike threads of the fungus grow over the fallen plants. Preventive measures. — Damping-off can usually be controlled satisfactorily by seed treatment and postemergence spraying. Seed that has been treated with corrosive sublimate, washed, and dried, should be treated again with yellow cop- per oxide dust at the rate of 1 teaspoon per pound of seed. If seed has been im- mersed in New Improved Ceresan, no other treatment is necessary. After the seedlings are up, spray at intervals of 7 to 10 days with normal Semesan solu- tion— 1 level tablespoon Semesan stirred into 1 gallon of water. Humid conditions and inadequate ven- tilation favor development of damping- off. Locate plant beds on well-drained soil covered with about ^ inch of nematode- free sand. This arrangement allows the surface to dry more quickly so that con- ditions are less favorable to the disease. After seedlings emerge, water the beds sparingly, and keep them well ventilated. When climate permits, open the beds by midmorning, water them, and leave them open until well into the afternoon. Do not water again in the afternoon, before covering the beds, even if the surface soil appears dry. Keep the surface as dry as possible whenever the plants are covered. Fusarium wilt is caused by the soil fungus Fusarium oxysporum f. lycoper- sici. It is a serious problem in certain regions where soil temperatures are high, and causes some losses in the early staked crop of the San Joaquin Valley and in the canning crop of the Delta and the Sacramento Valley. In general, it is not serious in coastal areas. This species of Fusarium attacks only tomatoes. It re- mains in the soil from year to year, and enters the plants through their roots. It is favored by soil temperatures of 80° F and above, and is most severe on the lighter, well-aerated, well-drained types of soil that heat up quickly. It may be brought into fields on infected trans- plants and may also be seed-borne. Symptoms. — Leaves of infected plants turn yellow, usually on one side of the plant at first. Later, the plant dies pre- maturely. The woody cylinder of the stem turns light brown, but it does not crack open, nor is the pith destroyed, as with bacterial canker. Do not confuse Fu- sarium wilt with Rhizopus canker, in which one branch turns yellow, and has an early-ripened and rotted fruit attached to it. Preventive measures. — Plant wilt- resistant varieties where soil is infested. (For a discussion of varieties, see pages 11-12.) Verticillium wilt is caused by the widespread soil fungus Verticillium albo- atrum. This disease is most serious under the cool conditions of the coastal districts, and is most prevalent in fields previously planted to tomatoes. The fungus persists in the soil from year to year. It infects other plants besides tomatoes, among them strawberries, cotton, and young stone fruit trees. [35] Symptoms. — Older leaves die prema- turely, and when the stem is cut near the ground, a brown discoloration is seen in the woody cylinder. The premature dying of the leaves exposes the Iruits to sun- scald. Infected plants may wilt tempo- rarily following heavy irrigation. Preventive measures. — Crop rota- tion is advisable. Although not resistant to infection, Early Santa Clara and Pear- son varieties show some tolerance to Verticillium wilt. Bonnie Best and San Marzano varieties are more severely in- jured. Late blight is caused by the fungus Phytophthora infestans. It sometimes re- sults in losses from fruit infection in the late fall crop in San Diego, Orange, Los Angeles, Ventura, and Santa Barbara counties after early fall rains. Infection also occurs in plant beds in the spring. Symptoms. — Brown or black blotches appear on the leaves and stems (fig. 24) . These spots enlarge rapidly, and cause blighting of the tops. Brown areas also appear on the green fruits. These areas are lobed at the margin and slightly sunken, with a somewhat corrugated sur- face that is firm and hard to the touch (fig. 25) . These lesions enlarge over half or more of the fruit surface, sometimes with three or four lesions on the same fruit. It is difficult to detect the beginning of infection when the green fruit is packed; the lesions develop rapidly in transit and during storage in the ripening rooms. This fungus usually affects only the outer walls of the fruit where it pro- duces a shallow, dry rot. However, other rot-producing organisms often enter the fruit through the blight lesions. Under very moist conditions, a whit- ish, velvety outgrowth of the fungus ap- pears on the leaf and stem lesions. This Fig. 24. Left: Symptoms of late-blight infection on tomato leaf. Blotches are at first water- soaked, later become greenish-brown or black. A white mold forms on undersurface. Fig. 25. Right: Symptoms of late blight on tomato fruit. Small, greenish-brown blotches enlarge and later become dark brown. Interior tissues become water-soaked and soon decay. :,r -* moldy growth is formed by the sporo- phores and spores of the fungus. The spores may be spread by wind and infect other plants. Preventive measures. — Late blight may be prevented by spraying or dusting with a copper fungicide. Since the fungus may remain in old, overwintered tomato plants and be carried from them to seed- lings or to young plants in the plant bed, the grower should destroy all overwin- tered tomato plants in the neighborhood of his plant beds. Early blight is caused by the fungus Alternaria solani. It sometimes occurs in the plant beds in early spring after pro- longed wet weather, and occasionally ap- pears on the maturing crop along the coast. Symptoms. — Small, dark brown spots appear on the leaves (fig. 26). When closely examined, these show a series of concentric rings. Black cankers also ap- pear on the stems of young plants, and small spots or large, brown, stem-end lesions show up on the green fruits late in the season (fig. 27). Infected plants may also be dwarfed, and what few fruits form may ripen prematurely. Control. — Spray plant beds with yellow copper oxide— 1 ] /2 pounds per 100 gal- lons of water. This will check the disease. Preventive measures. — Do not use plants from infected beds, particularly if they show any stem infection. If infected plants are set out in the field, the stem lesions continue to enlarge, finally gir- dling and weakening the stem. This pro- duces collar rot (fig. 28) , which weakens the stem so that it may break when the plant is whipped about by wind. If early blight has previously caused trouble in a planting area, move the plant beds to a new location. Fig. 26. Top: Early-blight leaf infection. This disease occurs in plant beds in wet seasons. Fig. 27. Bottom: Early-blight lesions on green tomato fruits. Fig. 28. Collar rot resulting from plant-bed stem lesions of the early-blight fungus, Alternaria solani. The stem eventually breaks as the plant is whipped about by the wind. Pleospora rot, caused by Pleospora lycopersici (Macrosporium sp.), affects the stem end of the ripening fruit (fig. 29) . Infection enters through cracks and wounds near the stem end, where a firm, dark brown spot develops. (Other fungi may also infect growth cracks and cause rotting of ripe fruits.) Temperatures be- tween 65° and 70° F favor most rapid development of the rot. It has caused considerable loss in November and De- cember shipments to eastern markets. 11 Rhizopus fruit rot and stem blight is caused by a fungus which enters the fruit through growth cracks, or openings caused by worm damage or other in- juries. It usually attacks fruits under heavy foliage in areas where humidity is high. The canning tomato crop in the interior valleys suffers considerable dam- age from this disease. Symptoms. — Infected fruit becomes a soft, watery mass, then loses the water contents and dries up on the stem (fig. 30). The fungus may spread from the fruit to the fruit spur, thus blighting the entire cluster. It may also continue into the main branch where it forms a long, dark brown, sunken canker. Similar cankers may occur where infected fruits touch a near-by stem, sometimes girdling the stem. Once the fungus enters a main branch of the plant, the leaves show a Fig. 29. Pleospora rot. This stem-end rot causes some loss in late fall shipments to the east from the Salinas Valley. i Fig. 30. Rhizopus rot of the first fruits to ripen. From the rotted fruit, the fungus may invade the fruit stem and finally girdle the main shoot. yellowing and blighting that might be mistaken for Fusarium wilt. Preventive measures, — Irrigate care- fully, to keep excess moisture from col- lecting under the plants. Remove rotten and damaged fruits at the first picking. This will help keep down losses. Buckeye rot is caused by a soil- inhabiting fungus, Phytophthora capsici. It occurs on green fruits that have been in contact with wet soil or irrigation wa- ter, particularly in the fall green-wrap crop in the Brentwood district. Symptoms. — Lesions are light brown, firm, leathery, have lobed margins and, sometimes, broad, concentric zones (fig. 31). These lesions enlarge rapidly and soon involve the entire fruit. Fig. 31. Buckeye rot caused by Phytophthora parasitica may occur on green fruits in contact with wet soil or irrigation water in the Brentwood green-wrap crop. This rot may resemble late blight, but foliage is not affected. Leaf mold. — The leaf mold caused by Cladosporium julvum usually appears only on greenhouse tomatoes, although it may occasionally occur on staked toma- toes in fields near the coast. Symptoms. — Large, yellow patches ap- pear on the upper surface, with a brown, velvety growth on the lower side. Infected leaves die prematurely. Preventive measures, — Clean up and disinfect the greenhouse before plants are set out. Keep the relative humidity low by adequate ventilation and heating. Irrigate properly. These measures will cut down leaf-mold losses. Bacterial canker is caused by a bac- terial organism, Corynebacterium michi- ganense. It causes stunting and early dying of the plants. Infection is carried both within and on the seed, and spreads under plant-bed conditions through the normal process of handling the trans- plants. The disease may also be spread by the cutting knife used in topping plants, by handling during transplanting, and by the practice of immersing freshly pulled transplants in water. Field carry over of infection does not seem to occur in Cali- fornia. Plants that show severe infection early in the season seldom produce any fruit of marketable size. Plants infected less severely may continue to grow and pro- duce some fruits fit for market. Symptoms. — The disease first shows up in a sudden wilting of the leaflets (fig. 32), often on only one or two branches, followed by a rapid dying of the wilted leaves. Wilted leaflets show first a pale green color, later a light tan, as they dry up. This is in contrast to Fusarium wilt, where the leaves turn yellow. Bacterial canker may also be distinguished from Fusarium wilt by the soft, mealy condi- tions of the interior tissues, as contrasted to the rather narrow, darker brown, firm, discolored tissue lying just under the stem surface of plants infected with Fu- sarium wilt. Infection is often confined to one, or a few, shoots on one side of the plant. These shoots may die, or be severely stunted, while healthy branches on the other side of the plant may con- tinue normal growth, giving the plant a one-sided appearance. Yellowish-white streaks frequently ap- pear on the stems and petioles, especially on the tender upper shoots where infec- tion is close to the surface. These streaks often crack when the tissue dries, and form open cankers— one of the main symptoms of this disease (fig. 33). The interior of diseased stems is yellowish to brown, and mealy, especially at the leaf nodes. The pith may be easily sepa- rated from the woody part. The infection also spreads into the leaf petioles, from which a yellowish ooze may be squeezed when a leaf is broken off. The canker bacteria may also pene- trate from the stem tissue into the fruit and sometimes the seed, without being noticeable. Fruits from severely diseased plants occasionally show a yellowish color in the seed cavity, which swarms with bacteria. Preventive measures: 1. Buy seed from a reliable seedsman. 2. Save seed only from disease-free fields. 3. Treat seed before planting. Place the seed in a thin cloth bag and immerse it for 5 minutes in a solution of 1 part New Improved Ceresan to 1,200 parts water. Use 1 gallon of solution for 1 pound of seed. Another disinfectant may be used— 1 part bichloride of mercury (corrosive sublimate) to 2,000 parts wa- ter. Soak seed for 5 minutes, with fre- quent agitation. Rinse in running water for 15 minutes. (The best method is to tie the open end of the bag to a faucet and turn the water on with enough force to wash the seed rapidly.) Spread the seed out to dry. (These treatments also help to control preemergence damping-off. ) When seed is dry, dust it with yellow copper oxide— 1 level teaspoon per pound of seed. This will help to control pre- emergence damping-off. [40] V Fig. 32. Effect of bacterial canker on seedlings. Right: Wilting leaves are first symptoms. Left: Later stage, with cankers on stem. 4. Locate plant beds in soil that has not previously been used for tomatoes. If old plant-bed lumber is used, disinfect it with formaldehyde (1 pint to 5 gallons of water) or copper sulfate (1 pound to 10 gallons of water). 5. Do not use plants from beds show- ing even a trace of canker. When buying plants, make reasonably sure that the grower took precautions to keep out this disease. 6. Do not top plants; the cutting knife may spread disease. 7. Do not immerse transplants in wa- ter while they are waiting to be set out in the field. Fig. 33. Left: Symptoms of bacterial canker on young plant found in field. Note cankers on stems and dead leaves on side branches. Fig. 34. Right: Field in Sacramento Valley showing tomato plants severely injured by bacterial canker. .*•£«> Bacterial speck is caused by the or- ganism Bacterium punctulans which may be carried on the tomato seed. Symptoms. — A black spotting of the leaves (fig. 35) occurs in plant beds under humid conditions and where over- head watering is practiced. The spots are greasy, and do not have the concentric lines that show in the lesions of early blight. This disease is not serious, and disappears after the plants are set out in the field. Another type of leaf specking some- times appears in the plant bed. This is not caused by a parasite, but may result from lack of some soil nutrient. The spots are small, brown, and closely crowded. They appear between the leaf veins. Spotted wilt is caused by a virus carried into the tomato field by flower thrips. It infects ornamentals, truck crops, and weeds, including celery, let- tuce, pepper, and horse bean, among the crops; calla, aster, nasturtium, tuberous begonia, gloxinia, cineraria, calceolaria, delphinium, dahlia, petunia, and zinnia, among the ornamentals; and nettle, Fig. 35. Bacterial speck on leaflets of young plants in field. chickweed, Jimson weed, wild lettuce, and mallow, among the weeds. Infected plants of any species may be a source of infection for tomatoes. The disease causes tremendous dam- age to tomatoes in the coastal regions, possibly because there is no freezing weather to cut down the reservoir of in- fection in winter crops, ornamentals, and weeds. Or it may be that there are more flower thrips in those districts. Serious damage has occurred in the interior val- leys only when the disease has been brought in on transplants grown near the coast, or has spread from near-by, year- round truck crops or plantings of orna- mentals. Late-season infection may occur to a limited degree in the Delta region and the Sacramento Valley, probably caused by infective thrips blown in from the Bay region. In parts of the coastal districts, spotted wilt is so prevalent that tomatoes cannot be grown profitably. In general, how- ever, the disease is scattered, and may affect 10 to 25 per cent of the crop by early infection, with considerable in- crease later in the season. The virus does not seem to spread from one tomato plant to another in the field, but is brought in by infective thrips from outside sources of infection. Frequently, spotted wilt oc- curs in plant beds which are located near ornamentals and home gardens, which are sources of infective thrips. Symptoms appear two to three weeks after infection occurs. This disease causes a sudden blighting and death of the tips of vigorously growing tomato plants (fig. 36). Careful examination shows that blighting is preceded by numerous cir- cular dead spots on the young leaflets, or by a bronzing (fig. 37) of the upper surfaces of these leaflets. Dead spots or streaks also appear on the leaf stalks and the stem. Occasionally, such plants are killed outright, but usually they remain alive, making little further growth and being greatly dwarfed and rosetted. The leaflets may show severe, mosaic symp- [42] Fig 36 Left: Leaflet shows circular brown spots characteristic of early stages of spotted wilt. Right: Streaking of stem and petiole, darkening of pith, and leaf blighting caused by spotted wilt. [43] .*vw Fig. 37. Yellowing, bronzing, and apical burn- ing of tomato leaflets, caused by spotted wilt. toms. Plants thus affected bear no crop. If young plants are infected in the plant bed, they show numerous small, circular dead spots on the leaves, and die quickly. Plants noticeably infected at this early stage seldom survive transplanting. When older, bearing plants are in- fected, the blighting of the growing points may or may not occur. But the fruits are clearly marked by circular patterns. On green fruit, the circles may be light and dark green (fig. 38). On ripening fruit, circular yellow spots may appear on a red background, or circular red spots on a yellow background. This is especially undesirable on late-season fruit to be shipped to eastern markets. When plants are infected with both the mosaic virus and the spotted wilt virus— a common condition late in the season— the spotted wilt symptoms are more severe, but the spots and patterns on leaves and fruit do not have the charac- teristic circular shape. There are exten- sive and irregular areas of dead tissue on and in the fruits. Control. — Field dusting with DDT re- duces the percentage of infection, but has not proved to be a satisfactory control even when as many as 6 applications have been made. In the greenhouse, spotted wilt may be controlled by fumigating once a week or oftener to kill thrips. Preventive measures, — Locate plant beds for tomatoes as far away as possible from home gardens or flowers that har- bor thrips. One variety— Pearl Harbor— is fairly resistant to spotted wilt, especially to early infection. It bears abundantly, but the fruits are small except under very favorable growing conditions. Curly top in tomatoes is caused by the same virus that causes curly top in sugar beets. It is spread by the beet leaf- hopper, and is the most serious tomato disease in the southern part of the San Joaquin Valley. During certain seasons, it may also infect the late crop in the northern part of the valley, especially near the foothills, and early tomatoes throughout the valley. The disease may also appear in the Sacramento Valley and south of the Tehachapi range. In- fected plants usually do not die, but they Fig. 38. Spotted wilt on tomatoes. Circular and concentric chlorotic patterns on green fruits. are a total loss so far as marketable fruit is concerned. The prevalence of curly top depends upon the number of infective leafhoppers that invade the fields. In the spring, the leafhoppers move from weeds, in their natural breeding areas, to cultivated sec- tions. The principal natural breeding areas are the foothills along the northern part of the San Joaquin Valley, and the valley floor at the south end. In addition to tomatoes and sugar beets, melons, spinach, flax, and many ornamentals and weeds are susceptible to the curly top virus. Symptoms. — The leaflets roll in toward the midrib (fig. 39) which, together with the leaf stem, curves downward. This gives the leaf a drooping, but not wilted, appearance. Leaves become thick, stiff, and yellow. The plant becomes erect and rigid, and is stunted because all growth stops. The leaf veins and stems turn pur- ple. Infected plants are stiff and brittle to the touch, and rattle when shaken. Most of the infection occurs during the early growth of the plant, and infected plants bear little or no fruit. What fruits are produced ripen when very small. The beet leafhopper lives only a short time on tomatoes, and there is relatively little spread of the virus from one tomato plant to another. Most of the danger comes from leafhoppers that enter to- mato fields from beets or other crops in- fected with curly top. Tomatoes often become infected after the harvest of beets in near-by fields. Control and preventive measures. To date, there is no adequate means of controlling or preventing tomato curly top. Tomato mosaic, a virus disease, is more prevalent and widespread, but less destructive, than either spotted wilt or curly top. It is not confined to any special areas of the state. This disease is easily spread by contact, such as handling the plants when setting them out in the field. The mosaic virus is occasionally seed- Fig. 39. Dwarfed tomato plant naturally in- fected with curly top virus. Leaves roll inward. borne, and one seedling among hundreds may be infected. A few of these seedlings in the plant beds are a dangerous source of infection when plants are set out in the field. There is also evidence that, in field seeding, the cultivator may spread infec- tion along the row from an occasional infected plant. The mosaic virus is prevalent in the tobacco crop. Because it withstands pro- longed drying, it is present in much com- mercial smoking and chewing tobacco, an important source of infection for tomatoes. Workers who have handled cigarette, cigar, pipe, or chewing tobacco may infect seedlings while they are being transplanted to the plant bed, and may spread the infection still further in pull- ing the transplants and setting them out in the field. [45 Fig. 40. Fernleaf, or shoestring, mosaic caused by the cucumber mosaic virus spread by aphids in the plant bed. is Symptoms. — The leaflets become mot tied and puckered, and the plant slightly reduced in size and yield. Some strains of the virus cause a rather bril- liant mottling of the leaves similar to that in yellow or aucuba mosaic. This type frequently produces a faint calico pattern in the fruit coloring, which usually, but not always, disappears at maturity. Early in the season, when the weather may be cloudy and temperatures low, the foliage symptoms are more extreme, and may be mistaken for fernleaf mosaic. Later foliage, however, produced under higher temperatures, shows typical mild mottling. Preventive measures. — Anyone working with tomatoes should wash his hands with ordinary laundry soap before handling the plants. This removes any virus which may be on the hands after using tobacco. Direct field seeding, which eliminates handling, greatly reduces the amount of mosaic. Fig. 41. Effect of fernleaf mosaic on tomato fruits. A [46] Fernleaf mosaic is caused by the virus of western cucumber mosaic. It is carried by aphids, usually in the plant bed before seedlings are set out in the field. Frequently, a few scattered plants show this shoestring or fernleaf type of mosaic, and heavy outbreaks have occurred in the Brentwood area. Symptoms. — The plant is greatly dwarfed and the leaflets are so narrow that little more than the midrib is left (fig. 40) . The fruits are usually dwarfed and misshapen (fig. 41 ) , and few or none of them salable. Preventive measures. — Spray plant beds with nicotine or rotenone if aphids are present. Destroy any plants of the cucumber family and any weeds that are near plant beds. Such plants may be sources of infection. Root rot is caused by Rhizoctonia, Fusarium, Pythium, and possibly other soil fungi, and results in serious losses in tomato fields. It is likely to be most serious on heavy, poorly drained soils. Heavy irrigation early in the season may leave the subsoil waterlogged. When the plant roots come into contact with such soil, they may be subject to attack from soil-rotting fungi. Thus the plants do not develop a normal, deep root system, and may wilt and die as they grow larger, because their shallow roots cannot sup- ply them with enough water for normal growth (fig. 42). Roots of tomato plants may also die because of insufficient soil aeration. This condition may result when irrigation water is allowed to stand between the rows for too long a time. Preventive measures. — Root rot may be overcome to a great extent by follow- ing the practice of frequent, light irriga- tions when plants are small, rather than of a few heavy irrigations. This prevents waterlogging of the subsoil, and allows normal, deep root development. Use a soil auger to test the subsoil for water content, in determining the plants' irriga- tion needs. Blossom-end rot is apparently caused by high temperatures and insufficient soil moisture and usually occurs on the first fruits that set. In some fields, it appears to have resulted from delaying the first irrigation too long. This disease is not infectious, but by killing fruit tissue, it provides a point of entry for rot-produc- ing fungi which aggravate the trouble. Symptoms. — Surface tissues at the blossom end of the fruit die, forming a large, flattened, brown area (fig. 43) . Yellowing and sunscald. — When the older leaves of the tomato plants die too soon, the fruits are exposed to the sun. This exposure may cause two types of injury. Usually, the stem end of the fruit Fig. 42. Root rot causes death of plants in wet soil. Fig. 43. Symptoms of blossom-end rot on tomato fruits. does not turn red, but remains yellow (fig. 44). Often, however, the injury is more severe, and the exposed side of the fruit may develop a large, light-colored, dead area (sunscald). This area is often invaded by molds. Growth cracks and catface. — Growth cracks at the stem end of the fruit provide an entrance for rot-producing organisms. Catface is an enlarged, ugly scar at the blossom end. Alkali injury. — In certain areas of some fields, the margins of the tomato leaves show browning (fig. 45) which tends to extend in between the veins. Psyllid yellows is not a virus disease, but is caused by an insect, the tomato psyllid. Apparently, as the psyllids feed, they inject some toxic substance into the fruit. This disease occurs mainly under cool coastal conditions, and in the early crop near the Salton Sea. Symptoms of this disease are somewhat like those of curly top, but the young leaves are more purple, leaves and stems are not so brittle, and the plant will re- sume normal growth if the psyllids are killed. The very young leaflets are puck- ered, dwarfed, and folded upward along the midrib. The leaf stems are curled and twisted. At this time, the margins and veins of the leaflets become purplish. Control. — Sulfur dust has been found to be effective against psyllids. Fig. 44. Left: Yellow-end (or green-end) caused by exposure to sun. Stem end does not color properly when fruit ripens. Fig. 45. Right: Marginal and interveinal browning of leaflets prob- ably caused by excess alkali in the soil. ^3901 INSECTS ATTACKING TOMATOES Two types of insect damage affect to- matoes in California. Direct damage is caused by insects that feed on roots, foli- age, or fruit. Indirect damage is caused by certain insects that transmit virus dis- eases. The latter are discussed under the section on tomato diseases (page 35). The control of many tomato insects and related pests has been investigated and much information has been obtained on the effectiveness of various insecticides and the proper time of application under northern California conditions. The tomato insect control program has undergone a marked change since the development of new insecticides, such as DDT and DDD. These have proved to be, on the whole, much more effective against tomato pests than were the old, standard insecticides, such as calcium arsenate and cryolite. Furthermore, the hazard of drifting dusts appears to be less with the new materials than with cal- cium arsenate. Although the new insec- ticides look very promising, they have not been in use long enough to warrant any final statement concerning their use in the tomato insect control program. They must still be used with caution. During the past two years there has been, on occasion, a marked increase in a leaf miner infestation on tomato. Also, there has been some evidence that spider mites have increased, and the same ap- pears to be true of certain other pests not usually destructive to tomato. It is not known, at present, whether any of these pests will become major problems, or whether widespread applications of DDT and DDD have in any way affected their increase. It is interesting to note that al- though nearly the entire tomato acreage was treated with these insecticides in 1949, the problems encountered were fewer than those in 1948. However, until more is known concerning the full effect of the new insecticides, it is suggested that their use be limited to late-season applications for the control of caterpil- lars, and that the older, standard mate- rials be used in the early-season control program. This division allows for the use of the new insecticides during the most important and critical time. Even during that period, however, they should not be applied without good reason, and never at a higher dosage than the one recom- mended. Although DDT is not recom- mended for general use in early-season treatments, it might, under conditions of severe infestation, be lightly and evenly applied for the control of certain pests, such as flea beetles. The control of tomato pests naturally falls into an early- and late-season pro- gram. The pests involved early in the season are usually different from those encountered later after the plants are well established in the field. Early-season pests attack from the time the seed is sown until the plants have become well estab- lished in the field. The more important ones include the seed-corn maggot, cut- worms, darkling ground beetles, thrips, flea beetles, and wireworms. Aphids, vegetable weevils, grasshoppers, slugs, and snails are sometimes annoying, and under certain conditions the tomato mite may require an early treatment. The late-season program covers the pe- riod from about June 15 to the end of the growing season. The important pests at this time are the tomato mite and a number of species of caterpillars which, if left unchecked, would destroy the crop in many cases. EARLY-SEASON PROGRAM Insects and other pests are not always troublesome either in plant beds, after transplanting to the field, or even where the seed is planted directly in the field. However, a grower should watch his plants carefully and be prepared to take [49 action if a serious situation is indicated. The presence of a few insects does not necessarily mean that a destructive popu- lation is developing, because in any plant bed or field a few pests of one kind or another can usually be found. Therefore, the rinding of an insect or two should be no cause for alarm, although a very few grasshoppers have been known to be highly destructive to a germination stand of field-sown tomatoes. Darkling ground beetles. — These small, dull black or bluish-black are beetles that measure scarcely % inch in length. They live in and on the surface of the soil and are destructive chiefly be- cause they eat off or girdle plants just above the ground level. Damage usually occurs after the tomato plants are trans- planted in the field. Control. — If this pest is suspected, dust the base of the plants and the soil about them thoroughly with hydrated lime the same day the plants are set in the field. Flea beetles. — These are small, dark colored beetles that measure only about Yiq inch in length. They jump like fleas, especially when disturbed, and damage tomatoes by eating small round holes in the leaves. Where an infestation is severe, defoliation may result. Injury usually oc- curs after transplanting and during the period when the plants are becoming established. Controf. — Dust the plants thoroughly with a 50 per cent cryolite dust or with calcium arsenate. Under severe condi- tions of infestation, a 5 per cent DDT dust may be used, but to prevent plant injury apply it thoroughly but lightly. Vegetable weevil. — This is a brown or buff-colored snout beetle that measures about % inch in length. It is sometimes destructive in localized areas. Confrof. — If control is needed, treat the plants with a dust that contains at least 50 per cent cryolite. To insure protection, cover the foliage and the ground about the base of the plants thoroughly with the dust. Wireworms. — These are the imma- ture stages of "click beetles." They have smooth, shiny, cylindrical bodies, tough skin, and are usually yellow or brownish in color. They live in the soil and most of the destructive species measure 1 inch or less in length. They injure plants either by cutting off roots or by penetrating into the root and up into the stems of young tomato plants. Wireworms are most likely to be a pest on the lighter soil types. Injury may occur in the seedbed, although the bulk of it takes place in the field after transplanting. Confrof. — The method of control used depends upon whether treatment is made before planting or at the time of setting out transplants. Before field seeding, plant-bed seeding, or setting out trans- plants, several methods may be used. 1 . Fumigate with ethylene dibromide mixture at the rate of 2 gallons of actual chemical per acre, or with dichloropro- pene mixture at the rate of 40 gallons per acre, using field fumigating equipment. In seed beds, use hand weed-gun applica- tors. Allow at least two weeks to elapse be- tween fumigating and planting. 2. The use of lindane, DDT, chlor- dane, or other chemicals applied to the soil surface and disked into the soil should be limited to seed-bed treatment unless otherwise recommended by local agricultural authorities. For seed-bed treatment, lindane sprayed on the sur- face of the soil, at the rate of 0.5 pound per acre, and worked into the upper 2 to 3 inches just before seeding, has proved effective. 3. Tomato seed can be treated with lindane at the rate of 8 ounces of 25 per cent powder to 100 pounds of seed. This treatment controls wireworms attracted to the seed at the time of germination. Lindane can be used with the standard fungicides in seed treatment. The water applied at the time of trans- planting in beds or in the field can be treated with lindane at the rate of 1 ounce of 25 per cent material in 100 gallons of [50 water. This treatment is effective and to date has given no indication of affecting growth or imparting off-flavors. Growers should proceed with caution, however, as adverse effects may occur which cannot be foreseen at this time. In peat soils, one- half again of the suggested dosage may be necessary for control. Crickets. — These large, brown to black, swiftly moving insects with long antennae or feelers are so well known that a detailed description is not needed. They feed at night and are likely to be most troublesome in warmer climates and in regions where there is considerable un- cultivated land. Most damage is done at the time of transplanting, and where abundant, crickets will cut off the newly set out seedlings. Control. — Poison bran baits will give some relief, but if they are to be at all effective they must be applied several days in advance of transplanting. The dust treatment, as recommended for the control of darkling ground beetles, gives protection. Dusts that contain chlordane are also effective against crickets, but if you use them, follow the directions on the container carefully. Seed-corn maggot. — This pest is a larva of a fly. It is legless, has no distinct head, and is nearly white. The seed-corn maggot attacks the germinating seeds and roots of tomato, and is a pest during the seed bed period. Injury by the pest is en- couraged by cold, moist, poorly drained soils. Control, — No highly satisfactory con- trol of this insect has been developed. If you think the pest is present, some relief may be obtained by dusting plants lightly but thoroughly with a 5 per cent chlor- dane dust. To prevent injury, do not over apply the insecticide. Cutworms or army worms. — These insects are the caterpillar stage of a group of medium-sized, dull-colored moths. Those important in the early season are night-feeding species, which are somber in color and when full-grown are 1% to 2 inches long. During the day, they hide in the soil and debris. Cutworms cause injury by cutting off the young seedlings or newly transplanted plants below or above ground. They also feed on the foli- age, and while a plant may not be cut off, it may be seriously defoliated. Injury by cutworms is most likely to occur where weedy fields, or fields containing con- siderable growing vegetation or sod, have been recently prepared for planting. Control. — If cutworms are thought to be present, scatter a commercially pre- pared poison bran bait over the field at the rate of 25 pounds to the acre. This should be done just before dusk sev- eral days before transplanting. Dusts used according to recommendations for the control of flea beetles should be of some benefit if the plants have already been set out. Aphids. — These are such familiar pests that there is no need to describe them. They obtain their nourishment by inserting their needle-like mouth parts into the plant tissue and sucking the plant juices. Aphids cause damage indirectly by transmitting a virus disease of tomato, but they rarely suck up the plant juices sufficiently to cause direct damage of an economic nature. Frequently, following transplanting, many aphids may be found on the recently set out plants. These usu- ally prove to be the green peach aphid which has migrated from other hosts. Such infestations usually die out and control measures are seldom, if ever, necessary. Another aphid sometimes en- countered is the potato aphid. Only rarely has it been found in destructive numbers. Control. — Where control is necessary, apply a number 10 (4 per cent actual nicotine) nicotine dust. Thrips. — These are small, slender in- sects with mouth parts developed prima- rily for sucking. They are about % 5 of an inch long, and the adults have two pairs of fringed wings, carried length- wise over the back. Both the young and the adults cause damage. Their rasping [51] and puncturing of the surface cells re- sult in a silvering of the leaves, stems, and fruit. Besides causing this direct in- jury, thrips transmit the serious spotted wilt virus disease of tomato, and once a plant is infected, there is nothing that can be done to stop the disease. Thrips are common insects that can be found in most tomato fields. Usually they are not present in destructive numbers, although occasionally injurious popula- tions are encountered. Where growing and cultural conditions are excellent, the plants will usually outgrow the injury caused by feeding. Control. — Where injury is severe, some relief can be obtained by thoroughly dust- ing the plants with a number 10 nicotine dust (4 per cent actual nicotine) . A 5 per cent DDT dust, lightly and evenly ap- plied, will give excellent control, but its use is not recommended unless a very serious infestation is encountered. The DDT dust should contain 50 per cent sul- fur as a control for the tomato mite. Grasshoppers. — Occasionally, grass- hoppers may be destructive. Where con- trol is required, application of chlordane at the rate of 1% pounds of actual mate- rial, per acre, has given satisfactory re- sults. Promising results have also been obtained with toxaphene. Tomato psy I lid. — This insect is about the same size as aphids, to which it is closely related. The adults resemble miniature cicadas and are grayish marked with white. All damage is done by the small, flat, elliptical, scale-like nymphs or immature forms, which vary in color from light green to orange. The nymphs are somewhat similar to those of certain whiteflies, and are normally found on the undersurface of the leaves. They have a row of wax glands, and when there is a large infestation, the white wax which is secreted may be seen on the leaves and even on the ground about the plants. The nymphs obtain nourishment by sucking cell sap, and cause injury by injecting a toxic substance into the plant. This causes a stunting of the plant and a yellowing and curling of the leaves— a condition known as "psyllid yellows." Damage by this pest in California is localized and is usually limited to the cooler coastal re- gions. Control. — Dust the plants thoroughly with sulfur. Begin applications when the first evidence of infestation is detected, repeat at two-week intervals until the pest is thoroughly controlled. Snails and slugs. — These well- known pests have chewing mouth parts and feed chiefly at night. They are seldom a pest of tomato, although they have oc- casionally caused annoyance about seed beds. In the presence of high moisture conditions and dense foliage, slugs have been found feeding on fruits of tomato in the coastal area. Control. — Where control is needed, scatter a commercially prepared poison bran bait over the infested area. This bait should contain both calcium arsenate and metaldehyde. For best results scatter the bait at dusk on wet ground. Tomato mite. — This pest is con- sidered more fully in the section, "Late- Season Control Program" (page 53). It is mentioned here because, under cer- tain conditions, it may become a pest in the early season. Petunia is an important overwintering host of the tomato mite, and therefore tomato beds should not be located near such plantings. If possible, petunia plants near tomato fields should be destroyed. Control. — If a tomato mite infestation should be detected, it can be controlled promptly by treating the field thoroughly with a sulfur dust. Root-knot nematode. — This para- site, which attacks the roots of many kinds of plants, is a small, round worm of almost microscopic size. It causes the formation of gall-like swellings or knots on the roots of tomatoes. The adult nema- todes are imbedded in these galls. Heavily infested plants become weakened and may eventually die. The first above- [52 ground indications of the presence of this pest are poor growth, stunting, and the yellowish appearance of the plants in the field. The tomato is very susceptible to in- jury by the root-knot nematode and should not be planted in fields known to be heavily infested. It is frequently pos- sible to secure reasonable control of this pest by growing such unfavorable host crops as barley, wheat, oats, and other grains before the tomato crop is to be planted. Control, — The root-knot nematode can be controlled by the fumigation of the soil with certain chemicals. The most ef- fective of these are the fumigants which contain 1, 3, dichloropropene, sold under the trade names of Shell D-D and Dow- fume N. These materials usually give satisfactory control of root-knot nematode when applied at the rate of 200 pounds per acre. Ethylene dibromide mixtures are also effective under conditions of moderate infestation, particularly in the coastal areas. Application is usually made at the rate of 3 to S 1 ^ gallons of actual ethylene dibromide per acre. In general, fumigation is effective for only a single season. Special commercial applicators are available for applying the above- mentioned fumigants. Caution: These fumigants are toxic to plants, and a field should be treated at least two weeks in advance of planting. Where trees and shrubs are growing nearby, treatments should not be made within the drip areas of such plants. The chemicals are also toxic to man. If they are spilled on the skin, wash the affected area thoroughly with soap and water. Clothing that has come into contact with fumigants should be cleaned or washed before being worn again. LATE-SEASON PROGRAM This is the most critical period in re- gard to the control of insect and related pests of tomato. Usually, during this time, a serious attack by one or more of the pests can be expected. The severity of the infestation by the several pests varies from district to district and year to year, but in all cases a grower must be pre- pared to combat attacks. The first pest to be encountered is the tomato mite, followed through the season by a number of caterpillars that must be controlled. The most important of these are known by the common names of yel- low-striped armyworm, beet armyworm, alfalfa looper, various night-feeding cut- worms, tomato pinworm, potato tuber moth, tobacco hornworm, tomato horn- worm, and the corn earworm. The pests and their habits will first be considered, and this will be followed by a program designed to give efficient control through- out the entire late season. The tomato mite feeds and repro- duces on a number of cultivated plants, notably tomato, potato, and petunia. It reproduces from eggs, and passes through many generations in a season. Continu- ous reproduction has been reported from early May until frost. The mite is too small to see with the Fig. 46. The tomato mite, enlarged 40 times. (From Bui. 707.) [53 naked eye, but under the microscope it appears as somewhat pear-shaped, and tannish-white in color (fig. 46) . It crawls about slowly on the surface of the leaves, stems, and fruit of the tomato plant and sucks out the cell contents. The infesta- tion usually starts near the ground and, as it progresses up the plant, the lower leaves become dry, giving the plant an unhealthy appearance. The color of the stems and leaves frequently becomes greasy bronze or russet. If not controlled, the pest causes seri- ous defoliation which is particularly rapid during periods of hot weather. The result is sunburned fruit and crop loss. Tomato mite appears early in tomato fields and usually requires control meas- ures in advance of most of the other pests. The caterpillars. — The caterpillar is the second of four distinct stages of development which butterflies and moths go through: egg, larva (caterpillar), pupa (chrysalis), and adult (moth or butterfly). Damage is inflicted only dur- ing the larval, or caterpillar, stage. Moths lay the eggs but do no damage. However, they must be recognized as a warning of the caterpillars to come. The control pro- gram must be directed against the cater- pillars themselves. The life histories of all of the cater- pillars are somewhat similar. Eggs, which have been laid on the plant by the adult moths, hatch after three to five days. The small caterpillars eat their way to ma- turity, casting their skins several times as they grow. During this period they do their damage to plant, leaves, or fruit, each in his own way. On completing development as larvae, the caterpillars begin construction of their pupal cells. Most of the pests of to- mato will burrow into the soil, build their cells a few inches below the surface, and construct tunnels upward to within one- half inch of the surface for the subsequent emergence of the adult moth. The alfalfa looper, however, spends its pupal life in a light silken cocoon it has spun in a fold of a leaf, or in several leaves tied together, or in the debris under the plant. The pupae of the tomato pinworm and the potato tuber moth, on the other hand, are usually to be found at or near the soil surface. The pupal stage varies in length for each of the different kinds of caterpillars, and also varies with the weather. For ex- ample, the corn earworm has a pupal pe- riod of two to three weeks during the summer, but the fall broods will remain in this stage over winter. Egg laying begins. — When the pupal stage is over, the adult moths emerge, ex- pand and dry their wings, mate and, after a day or two, begin to lay their eggs in great numbers. Usually at dusk on warm days the female moths of the corn ear- worm may be seen flitting here and there, Fig. 47. Corn earworm (A) may spend its life in the fruit, causing damage shown at right (B). (From Bui. 707.) [54] seldom flying higher than the tops of the plants, and laying eggs at random over the vines. A single moth will lay 500 to 3,000 eggs during her lifetime. With the hatching of these eggs, an- other generation begins its life cycle. Some species, such as the tomato horn- worm, have three generations a season, but others, such as the tomato pinworm, pass through as many as seven or eight generations in a year. Know the pests by the damage they do. — While the life histories of all of the caterpillars are quite similar, the damage they inflict on tomatoes may differ widely. The visible evidence of this damage serves as the best clue to the kinds of pests present, and indicates the kind of treatment which should be applied. Corn earworm. — The corn earworm is considered the most destructive cater- pillar because of its abundance and wide distribution, and the fact that it normally completes its entire larval development in the fruit. This pest prefers corn and beans, and turns to tomato late in the summer when the former crops have passed their maturity and are drying up. If it becomes established in the tomato fields in August, there is still sufficient time for two broods to appear before to- mato harvest is completed. Where infes- tation is severe, more than 50 per cent of the tomatoes may be destroyed. The larvae usually enter at the calyx or stem end (fig. 47) and some are so small at the time they infest the fruit that one must look carefully to detect the point of penetration. The caterpillar may emerge from one fruit and enter another. The small corn earworm tends to enter developing tomatoes % to 2 inches in di- ameter. Therefore, the beginning of an infestation can be determined by picking and thoroughly examining fruit in this size range. A control program need not be started until 1 to 2 per cent of the fruit in this stage of development shows signs of infestation. Pick at least 300 fruits at random throughout the field to Fig. 48. Yellow-striped armyworm. Above: Moth of this species is grayish in color. Fore- wings have slate and buff markings; hind wings are silver and gray. Below: Typical injury to tomato by caterpillar. (From Bui. 707.) determine the degree of infestation. Late in the harvest season, the small larvae may enter the ripe fruit as well, causing the canner much annoyance because these infested fruits are nearly impossible to detect. Yellow-striped armyworm. — While occurring in greatest numbers on alfalfa, the yellow-striped armyworm in- fests many kinds of cultivated and native plants. Although not a serious pest of tomato every year, on occasions it is very destructive. Infestations in tomatoes arise from moths which fly into tomato fields, or from caterpillars which migrate from adjacent alfalfa fields when the latter are cut. This pest feeds both on the foliage and on the fruit of the tomato. It does not enter the fruit, but eats irregular holes in its surface (fig. 48). Its most serious attack on tomato occurs from July through the middle of September. Beet armyworm. — One of the most common and widespread pests in Califor- [55] nia, the beet armyworm, is to be found in tomato fields every year. At times, in cer- tain fields, it has been the most important caterpillar attacking tomato. The beet armyworm feeds primarily on foliage, but it will also seriously at- tack the fruit in which it eats single, or closely grouped, circular or irregular holes. In many cases the feeding is only superficial, and there would be little loss if rot and decay did not enter the wounds. This pest is most common and destruc- tive in the warmer interior valleys where it is abundant from late July until early November. In severe cases of infestation it is not uncommon to find an average of 25 to 50 caterpillars to a tomato plant. Alfalfa looper. — These caterpillars are easily distinguished from others be- cause they arch their backs when they crawl, hence the name "looper." The alfalfa looper eats foliage and rare- ly feeds on fruit. It occurs in fair abun- dance, but seldom causes enough damage to require special control measures. Potato tuber moth. — Tomatoes over a large portion of California are subject to infestation by the caterpillar of the potato tuber moth. They appear to be most prevalent in the coastal regions and the San Joaquin Valley. There is always the danger of a serious infestation developing where tomatoes follow potatoes and where there are vol- unteer potato plants. Usually, less than 5 per cent of the tomatoes in a field show infestation, but damage to as high as 57 per cent of the fruit has been found. These larvae prefer to enter the fruit at the calyx end and make a dry burrow through the core and the fleshy portions which radiate from it (fig. 49) . They may enter at any point, however. They usually spin a web over the entrance to their bur- rows, if these are exposed. The fruit must be carefully observed to detect damage. Tomato pinworm. — This caterpil- lar is a leaf-miner and leaf-folder, but during the last half of its larval existence it also frequently bores into the fruit. [56 Where abundant, the tomato pinworm may cause serious damage to the foliage, and nearly 100 per cent of the fruit may be infested. The larvae will enter the fruit at any point. They make dry burrows, are small, and usually do not penetrate very far into the fruit. After an infested fruit is picked, the caterpillar quickly spins a web over the entrance to its burrow, making its pres- ence hard to detect. Because the pinworm completes a num- ber of generations in a season, it becomes more serious as the season advances. Greatest damage is likely to occur where tomatoes are produced from early in the growing season to late in the fall. Night-feeding cutworms. — There are several species of cutworms which attack tomato only at night, and hide in the soil or surface debris during the day. §& «* Fig. 49. Injury caused by the potato tuber moth. (From Bui. 707.) Fig. 50. Defoliation like this is typical hornworm injury. (From Bui. 707.) Under some conditions they are likely to be quite destructive. These pests injure tomatoes by eating irregular holes in the surface. Tomatoes that rest on the ground are, in general, the most seriously injured. Hornworms. — The tomato horn- worm and tobacco hornworm are similar at all stages of development, and their damage to tomato is also similar. They feed on the blossoms and fruit but cause the most serious damage by stripping the leaves from tomato vines. If severe infes- tations go unchecked, hornworms may defoliate an entire field (fig. 50). Hornworms are particularly serious pests in the warmer interior valleys of the state. NATURE AND CULTURAL METHODS AID PEST CONTROL Control of caterpillars attacking to- mato would be a much more difficult problem if it were not for natural factors which tend to hold destructive pests in check. Important among these are preda- tors, parasites, and diseases. Weather, also, may have an adverse effect. In spite of these natural limiting fac- tors, some of the many pests are likely to reach a destructive level. The tomato grower can meet the problem in two ways. He can adopt cultural practices which are unfavorable to the pest, and he can employ specific pest-control measures involving the application of effective in- secticides. Natural enemies. — Caterpillars in- festing tomato are subject to the attack of a number of parasites and predators. The full value of these enemies has never been determined, but it is known that cer- tain of them are responsible in a large measure for some species of caterpillars not reaching a destructive level every [57 year. One of these, Hyposotor exiguae (Vier.), which attacks the corn earworm and the yellow-striped armyworm, has been observed, and is recognized as an important factor in controlling these pests. The action of the many parasites upon their host, and the influence they exert in regulating populations is a subject that is in need of thorough investigation. It is important that insecticidal control pro- grams be developed that will supplement the work of the natural parasites. Cultural methods. — The destruc- tion of crop refuse is a sanitary measure that should be practiced. It is particularly important in regions where tomato pin- worms or the larvae of the potato tuber moth are a problem. Where the pinworm is a pest, growing of an early- and late- season crop should be avoided if this is at all possible. If two crops are grown, destroy the refuse from the first crop by burning it or plowing it under just as soon as the harvest has been com- pleted. The practice of following potatoes with tomatoes should be avoided. Most exten- sive damage by the larvae of the potato tuber moth has usually been found in those fields where volunteer potato plants have been growing. Infestations by the corn earworm on tomatoes are likely to be most severe in areas where sweet corn and beans are grown. The farmer must encourage the destruction of crop refuse as soon as these preferred hosts are harvested. INSECTICIDE CONTROL PROGRAM The late-season control program should be well-integrated so that the crop will be protected from all the important pests throughout the entire bearing season. The first pest that must be considered is the tomato mite. This pest can be controlled by treating the fields with sulfur. Treat- ment should be applied not later than July 15, and in all cases before injury by the mite becomes apparent. If insecti- cides are incorporated with the sulfur, for, worm control, the sulfur content of such dusts should be 75 per cent. Under no condition should the sulfur content be less than 50 per cent. If liquid applica- tions are used for this early treatment, apply at least 15 pounds of wettable sul- fur per acre. To insure good control of the tomato mite, the second dust applica- tion which is directed against caterpillars should contain 50 per cent sulfur. If a third dust application is made for cater- pillar control, sulfur may be omitted if there is no evidence of a developing to- mato mite population. The two most thoroughly commer- cially tested and effective insecticides, with one exception, for the control of caterpillars are DDT (dichloro-diphenyl trichloroethane) and DDD (dichloro- diphenyl dichloroethane) . These insecti- cides have resulted in good control where applied as dusts or concentrated sprays at the rate of 1% pounds of actual mate- rial per acre per application. This is equivalent to 30 pounds of a 5 per cent dust, or 3 pounds of a 50 per cent wet- table powder. Where coverage has been good, satisfactory control has been ob- tained with either ground or airplane ap- plication. With concentrated sprays, 3 pounds of a 50 per cent wettable powder have been used with 10 gallons of water. DDT dust is highly effective against all the important caterpillars with the ex- ception of the tomato hornworm Proto- parce sexta (Johan.). When DDT is applied as a concentrated spray, it gives good control, but a 5 per cent DDT dust is not effective in killing the larger, more mature worms. Therefore, a 5 per cent DDT dust should be used with caution in regions where hornworms are likely to be a serious pest. Another new insecticide that has shown considerable promise in controlling to- [58 mato caterpillars is a 10 per cent toxa- phene dust applied at 30 pounds per acre. This insecticide has been experimented with for three years and the results ob- tained approach those secured with DDT and DDD. This insecticide has given good control of all caterpillars where it has been used in combination with DDT. A dust that contained 5 per cent toxaphene and 3 per cent DDT, at 30 pounds per acre, produced good results. In sections where hornworms are likely to be a seri- ous pest, and a grower needs to apply a dust, this mixture, or DDD, might be a safer application to use than a straight DDT dust. The most critical period for caterpillar control is from about July 15 to the end of the season. Satisfactory control of the tomato mite as well as of the several species of caterpillars is usually obtained with not more than three applications of insecticides. Under certain conditions and in certain areas, fewer applications are needed. However, in no case should the first application, which is mainly di- rected against the tomato mite, be omitted. Remember: good control is de- pendent upon thorough and even appli- cation of the insecticides. The following is a generalized program suited to most of northern California. THE GENERALIZED CONTROL PROGRAM FOR NORTHERN CALIFORNIA The following schedule for applica- tions of insecticides is particularly adapted to northern California condi- tions, where canning tomatoes are pre- dominant. In the central and southern San Joaquin Valley the program should be put into operation as early as late May or June, and continued as long as there is evidence of pest damage. JULY 1-15 Because the tomato mite is the first pest to make an appearance, it should be treated first, by dusting with sulfur. This treatment probably will be needed by July 1 to 15. During this period, horn- worms, yellow-striped armyworms, and beet armyworms may be making their appearance. Where this occurs, an effec- tive insecticide should be used in con- junction with sulfur to control them. AUGUST 1-15 During early August the important in- sects to control are the beet armyworm, yellow-striped armyworm, and horn- worms. A suitable insecticide should be applied to check their damage. At the same time the application will control the few corn earworms which may be appear- ing. The insecticide should also contain sulfur to continue the control of the to- mato mite. SEPTEMBER 1-15 Early in September a third treatment is needed and is primarily directed against corn earworms, but should also be effective against armyworms and horn- worms which are certain to be present. If damage by the tomato mite is not ap- parent, sulfur may be excluded. SAMPLING Any application of insecticides should be based upon a knowledge of the insect pests present. An examination of from 200 to 600 fruits, depending on the size of the field, should reveal the kinds of insects present and the degree of infestation. These sam- ples should be taken at random from all parts of the field, as incidence of pests may vary widely from one spot to another. Insecticidal residues. — The ques- tion of poisonous residues always arises in connection with the application of in- secticides. The final authority concerning residues is the Federal Food and Drug Adminis- tration. Because no tolerance has been an- nounced for the presence of DDT and [59 related compounds in canned foods, it is imperative that residual amounts of these compounds be effectively removed before the products are canned. For this reason, residue studies were undertaken to determine the effectiveness of removal of DDT and DDD from toma- toes by washing methods similar to those used in commercial canneries. The test- ing was done by the National Canners' Association Laboratories, and the results were reported to the authors to supple- ment their control investigations. The results of these studies are briefly stated as follows : DDD and DDT on unwashed tomatoes picked the same day the insecticide was applied showed from 0.2 to 1.7 parts per million; the same fruit after washing showed from 0.1 to 0.7 parts per million. Juice prepared from the washed tomatoes contained 0.1 part or less per million of DDT or DDD; while the residue of the pulp after juice was removed contained from 2.7 to 4.3 parts per million of DDT or DDD. Subsequent studies have con- firmed these results and have also indi- cated that a 10 per cent toxaphene dust can be safely applied to tomatoes. From the above, it appears that there should be no serious residue problem so far as canning tomatoes are concerned if the insecticides are used as recom- mended in this circular. Where fruit is intended for the fresh market it should be washed or carefully wiped. ACKNOWLEDGMENTS Dr. MacGillivray wishes to express his appre- ciation for assistance received from various staff members, and for photographs provided through the kindness of the Associated Seed Growers, Ferry-Morse Seed Company, and the Union Pa- cific Railroad Company. Dr. Michelbacher wishes to thank the follow- ing growers for their cooperation: Harlan and Dumars of Woodland, Albert Bevis of Patter- son, and J. A. Molter of Davis. Thanks are also due to: E. O. Essig, W. W. Middlekauff, W. Harry Lange, Frank C. Lamb, N. B. Akesson, Edward Wegenek, Don Davis, and Charles Han- son; to J. R. Esty, Western Branch Laboratory of the National Canners' Association; and to the insecticide companies who furnished mate- rial for use in the investigation. In order that the information in our publications may be more intelligible, it is sometimes neces- sary to use trade names of products and equipment rather than complicated descriptive or chemical identifications. In so doing, it is unavoidable in some cases that similar products which are on the market under other trade names may not be cited. No endorsement of named products is intended nor is criticism implied of similar products which are not mentioned. 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. J. Earl Coke, Director, California Agricultural Extension Service. 30m-6,'50(B8980)LL