u & "*'. '/, Division of Agricultural Sci e n c e s ' Of A 6*^. ? UNIVERSITY OF CALIFORNIA CALIFORNIA AGRICULTURAL Experiment Station Extension Service BAVIS JAN 29 1958 LIBRARY MANUAL 24 Price, 25^ CONTENTS Soil and Climate • • • Varieties • • Cultural Operations ... 4 Early Market Cucumbers ... 7 Pollination • • • 10 Diseases ... 10 Insect Pests . . 13 Harvesting and Packing 16 HIS MANUAL is one of a series published by the University of California Division of Agricultural Sciences and sold for a charge based on returning only a portion of the production cost. By this means it is possible to make available publications which, due to the relatively high cost of production, or limited audience, would otherwise be beyond the scope of the University's publishing program. • CUCUMBER PRODUCTION in California GLEN N. DAVIS BERNARR J. HALL University of California Division of Agricultural Sciences Agricultural Experiment Station — Extension Service ! IBRARY UNIVERSITY OF CALIFORNIA DAVIS delicacy rather than a staple, the cu- cumber has nevertheless held a permanent place in man's diet for several thousand years because of its distinctive texture and flavor. Cucumbers are low in food value, containing about 96 per cent water and providing only 14 calories per 100 grams of edible portion; their nutritive value is slight. And yet they have a long record of popularity. In the Orient they have been cultivated for three or four thousand years. They are mentioned in the Old Testament as a food in ancient Egypt. Mi- grating farther westward, they were known to the Greeks and Romans, who introduced them into Europe, and they have been grown in America since the earliest settlements. Today the cucumber is one of Califor- nia's twenty most important vegetable crops and a popular member of the home vegetable garden as well. In terms of re- turns to the grower, cucumbers ranked eighteenth among all vegetable crops in California in 1956, when 6,600 acres planted to this crop had a market value of $4,824,000. Cucumbers grown for proc- essing accounted for approximately 3,600 acres, with a value of $1,901,000; the crop from the other 3,000 acres, valued at $2,923,000, was produced for the fresh market. Probably originating in India, cucum- bers are a warm-season vegetable. Com- mercial production in California is thus limited to the central and southern areas of the state, and principally to the coastal counties. The greatest concentration is in Alameda County, where more than 50 per cent of the crop for processing is grown. The next largest acreages are found in San Diego, Los Angeles, and Imperial counties, in that order. In other counties the acreage is somewhat limited and varies considerably from year to year. THE AUTHORS: Glen N. Davis is Professor of Vegetable Crops and Olericulturist in the Experiment Station, Davis. Bernarr J. Hall is a Farm Advisor, San Diego. JANUARY, 1958 Soil and Climate Cucumbers will grow on any fertile soil but they must have warm temperatures. Definitely a warm-season crop, cucum- bers are best adapted to an average monthly temperature of 65-75° F, which lasts from 50 to 90 days without extremes of hot or cold. They cannot be hardened to resist even light frosts and cannot be grown unprotected as a winter crop any- where in the state. Cucumber seed seldom germinates when the temperature is below 60° F. The optimum temperature for germina- tion is 95° F. Planting should be delayed until conditions are favorable for ger- mination. Cucumbers grow well on any fertile soil. They have been successfully grown on sandy clay loam, peat, muck, clay, and even somewhat light sands. Where the crops are intended for early market, the lighter soils are preferred. Pickling cucumbers are generally grown on heavier soil types, for in this case earli- ness is not important. Moisture and plant food supply conducive to large total yield are more generally met on the heavier soils. Very heavy yields of pickling cucumbers have been secured on peat soils in California. Since an abundant supply of organic matter is desirable, many states recom- mend preceding cucumbers with a legume cover crop. The cover crop should be turned under in time for it to decay before the cucumbers are planted. Manure is highly recommended as a source of organic matter. Cucumbers are sensitive to acid soils. They should be grown in a soil with a pH of 5.5 or higher. Most desirable is a soil with a pH of 6.0 to 6.5. It is not advisable to replant cucumbers in successive years or to grow them on soil recently planted to any of the other cucurbits, such as watermelons, cantaloupes, or squash, because of pos- sible damage from disease or insects car- ried over from the old crop. Satisfactory rotation crops are a legume cover crop or other noncucurbit plants, such as beans, celery, or cereals, which will re- plenish the soil with organic matter. Varieties The variety to plant depends first on the use to which the product will be put — fresh market or pickling. While many varieties of cucumbers are available, relatively few are of commer- cial importance in California. The vari- ety Marketer is the one most widely grown. Cucumber varieties are generally more or less arbitrarily lumped into two main categories — those grown for the fresh market and those grown for pickles. Slicing cucumbers vary in length from 6 to 12 inches and are usually harvested at a more mature stage than those for pickles. 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If cucumbers are a new crop for you, consult your local Farm Advisor regarding local varietal adaptation and preference. In addition to the varieties listed in the table, some others may prove desirable under certain conditions. The varieties Santee and Palmetto are resistant to downy mildew, while the varieties Niag- ara, Wisconsin SMR12, Ohio MR17, Ohio MR25, and York State have con- siderable resistance to mosaic. A few F^ hybrid varieties, such as Saladeer and Burpee's Surecrop, are available. These hybrids are resistant to mosaic and downy mildew. The variety Lemon, a small egg-shaped variety, is grown to a limited extent for market and more widely in home gardens. The West Indian gherkin is grown to a limited extent for pickling. This small, oval-shaped, very spiny fruit belongs to a different species than other cucumber varieties. Cultural Operations Growth habits of the cucumber — its root distribution in particular — demand care in cultivation. Preparing the land Careful soil preparation is essential to successful cucumber culture. Since the main considerations are earliness, qual- ity, and a fairly long picking season, the soil must be thoroughly prepared, especially where production costs are high. Land that was in seed or cover crop the preceding season should be plowed during the summer or fall to allow time for decay of the rough material turned under. Land previously planted to alfalfa can be successfully prepared by a shallow 1 6- to 8-inch) plowing followed by double disking and a deeper (8- to 10- inch I plowing within two or three weeks. Land previously in row crops should be disked and plowed as soon as the crops are harvested. Final preparation should be made about a month before planting so the soil can settle before the seeds are planted. \l this time the land is disked, harrowed. and leveled or floated. If these operations do not leave a smooth surface of well- pulverized soil, repeat one or more of the operations. Land prepared according to these di- rections is ready for planting crops that are to be grown on flat land without irri- gation for emergence. If the surface soil is too dry for rapid seed germination and emergence of young plants, irriga- tion water is applied in furrows adjacent to the planted rows. If an early crop is to be grown on beds, the preliminary operations are the same as those used for flat land. About a month before planting the land is made into beds 1% to 2 feet high and 4 to 6 feet from center to center. Where possible the beds should be constructed to extend east and west so that the southern slopes will be exposed to the winter sun. Irri- gation water is applied in furrows be- tween the beds. The beds can be laid out with a lister to which a marker is attached. The lister [4] PLANTING BY HAND This is usually done in three short rows that run at right angles to the irrigation furrow. makes furrows 8 to 10 inches deep, and the beds are formed by back furrowing with a walking plow or with a two-bottom tractor-drawn plow. A heavy tractor pull- ing six plows can be used to make two half beds in a single operation. The south side of the bed is harrowed and smoothed with a V-drag. The bed is then ready for planting. Planting Since cucumbers are susceptible to frost injury, open planting in the field should be delayed until danger of frost is past. In some areas earlier planting is made possible by using paper covers or caps to protect the young plants; this practice may speed maturity by two to four weeks. Planting may be done by hand in hills, or the seed may be planted in rows with drills that plant one to several rows at a time. Planting distances vary with the locality. Where the cucumbers are grown in hills, the hills are spaced 2 to 3 feet apart in rows 2% to 4 or more feet apart. Nine to twelve seeds are planted in each Here cucumber seed is being drilled by a machine that plants three rows at a time. ■::;«ii:?li hill b\ hand and covered with about 1 to 1 1 A inches of soil. When drilled into rows by machine, the seed is spaced thinly and evenly throughout the row. (Rows should be 4 to 6 feet apart.) Two to three pounds of seed should be enough to plant one acre, and care should be taken that the average planter does not drop too much seed. Thinning As a rule, cucumbers require thinning. After they have become well established, the stand should be reduced to two to three plants per hill. If they are planted in a continuous row, the final stand should consist of single plants spaced 6 to 12 inches apart. They can be thinned with a hoe along with the first hand weeding. Plants to be removed should not be pulled but cut to avoid disturbing the roots of the remaining plants. Fertilizers The kind and quantity of fertilizer needed depend largely on soil type and the amount of available nutrients already in the soil. These characteristics vary with the soil's origin and past history, including its treatment under cultivation. In California cucumbers often respond to applications of both nitrogen and phosphate fertilizers. Most of the soils in which cucumbers are grown, particularly in the arid interior valleys, are low in organic matter. Manure, if available, is especially desirable; if not, the humus content of the soil can be increased by plowing under alfalfa, clover, vetch, cow- pea, soybean, sesbania, cereal, and other soil-improving crops. Nitrogen. In the Imperial Valley and southern districts 60 to 75 pounds per acre of nitrogen should be applied, while as much as 100 pounds or more per acre may be needed for growing the pickling crop iti central California. Half the amount can be applied at planting, the remainder when the runners start. Dry fertilizer can be applied with a fertilizer drill a few inches to the side of and a few inches below the seed. Equivalent amounts of liquid fertilizer containing nitrogen can be added to the irrigation water. If heavy nitrogenous fertilizers have been applied to the preceding crop, cucumbers may not need additional nitrogen. Phosphate applications should be made early — preferably at, or shortly after, planting. Amounts of fertilizer that deliver 60 to 100 pounds of phosphate expressed as phosphoric acid (P.^O-) per acre should be applied. About 600 pounds per acre of a single super- phosphate (16 to 20 per cent P •>()-,) or proportionately less of the more concen- trated forms can be broadcast before bedding the soil. Phosphate fertilizers can also be banded into the beds just before planting — a few inches to the side of and a few inches below the seed, be- tween the seed row and the irrigation furrow. Equivalent amounts of liquid phos- phate fertilizer can be banded into the soil with special equipment, or they can be given in the irrigation water at plant- ing or even earlier. If liquid fertilizer is used, the irrigation water must be care- fully controlled to obtain uniform dis- tribution and to prevent excessive loss of fertilizer in the waste water. Phosphate fertilizer may not be needed if it has been used on the preceding crop. Fertilizers such as 11-48-0 or 16-20-0. which contain both nitrogen and phos- phorus, can be used to supply all or part of the nitrogen and phosphorus require- ment. Experiences to date have not indi- cated a response to the addition of potash. Cultivation and weed control Cucumbers should be cultivated from the time the plants break through the ground to keep the soil loose and free from weeds until the spread of the vines makes further working impracticable. Early cultivation may be fairly close to \(y\ ihe plants and at reasonable depths. After the roots begin to spread, the later, shallow cultivations should be farther away from the plants. A comparatively shallow-rooted plant, the cucumber has roots that often extend beyond the tips of the vines. Therefore, after the vines begin to run freely, culti- vation should be relatively shallow and not too close to the rows. Hand hoeing will generally be necessary early in the season when the plants are small. After the vines cover the ground no further cultivation can be given, but it is often necessary to go through the field and pull out weeds that are gaining a foothold. Weed control in cucumber fields may prove costly, especially if weeds in pre- ceding crops are allowed to mature and go to seed. Competitive weed growth should be reduced while the cucumber plants are small, and the field should be kept free from weeds until harvest is finished. Besides being highly competitive, cer- tain weeds may harbor virus diseases and insect pests, thus serving as reser- voirs of infection in the current crop. The use of chemicals for weed control in the cucumber crop is showing promise. One method, perhaps the more economical one, is to spray the plant row after seeding and before either the weed or cucumber seed germinates. Weeds be- tween the rows may be easily removed by cultivation. Chemical herbicides can also be applied to the ridged bed and ditch after the final furrow and bed are made, just ahead of first picking. This elimi- nates hand weeding in the plant zone and irrigation furrow. Two selective chemicals that show promise in controlling weeds in cucum- ber fields are N-l naphthyl-phthalamir acid and sodium isopropyl xanthate. Dosages may vary slightly depending on the amount of moisture following the application, soil type, kind of weeds, and cucumber variety tolerance. Before applying a herbicide consult your county Farm Advisor for informa- tion on local experiences and recom- mendations. Irrigation For maximum yields and high quality, cucumbers must have an adequate supply of moisture. In irrigation as in weeding, the plant's moderately shallow root dis- tribution must be borne in mind. The roots extend to a depth of only about 4 feet if no hardpan prevents root pene- tration to this depth. If the soil is filled to its maximum water-holding capacity before planting, by winter rainfall or preirrigation, addi- tional water at fairly frequent intervals is essential for maximum production. Generally, 18 to 24 inches of water is ap- plied during the growing season. Furrow irrigation is the most common method, although where the water supply is limited or costs are exceedingly high, sprinklers may be used. Early Market Cucumbers Need special planting methods and care during early growth. Producing early spring cucumbers re- requirements, production is limited to quires many special and varied opera- southern California. The early planting tions. Because of the plants' temperature may be made with transplants started in [71 mmagmmmmmws&M PLANT IN FLATS The planting board makes 100 marks in each flat— four or five seeds are placed in each mark. Photo left center shows sprouted flats in the greenhouse, by direct seeding in the field, or by both methods. Transplants. Cucumber plants for transplanting to the field are usually started in flats in the greenhouse in Janu- ary and February. The soil in the flat is marked with a pegged planting board (100 pegs per flat) , and four or five seeds are planted in each mark. This gives 100 clumps of four or five plants per flat. It takes five to six days from time of plant- ing seed to transplanting into the field. At this time the clumps are removed and set into place with a plant setter. Direct seeding. In the field, seed is planted in shallow depressions (often finger marks), which are parallel to, or at right angles to, the side of the irriga- tion furrow. The right-angle position in- sures that some seeds will get enough moisture for germination if there is a variation in the way the water soaks into the furrow. Twelve to 20 seeds are planted in each hill. Combination planting. To insure a good plant stand, some growers set out transplants and plant seed in a single operation. THEN TO FIELD To insure a good stand, some growers set out transplants and then plant seeds in the same hill. Transplants should be covered with mmm* V plants in a flat next to a newly planted flat that has half of the seeds covered. Photo at right shows plants being transplanted from flats to the field using a plant setter. For early market cucumbers, regard- less of the planting method, at planting time the hills are enclosed with hot caps to protect the transplants or germinating seedlings from frost and to speed their growth. To obtain a satisfactory stand, two to four replantings with transplants or seed are often necessary. At each in- spection for plant stand and replanting, the weeds are removed before the caps are replaced over the hills. As the plants develop and become crowded in the original small cap, the small caps are removed and replaced with larger tent caps. This change is usually made in late March, and at the same time the plants are thinned to two or three per hill and the weeds are re- moved from the area to be covered. The larger cover allows a larger area to be covered, resulting in more rapid plant growth. About the middle of April when the plants have filled the tents, the lee- ward end of the tents is unfolded. During this operation the area is again weeded, and the plant runners are gently guided out of the open end of the tent. As the plants develop and enlarge in the open- hot caps until they are big enough to require more room. Then the hot caps may be removed and larger tent caps used in their place. ing, the caps are lifted, permitting the plants to become acclimated as they grow out from under the tents. When the plants have runners 18 to 24 inches long, the tent covers are finally removed. In controlling pests while the plants are small, dusts are applied to the plants when the covers are opened, or applica- tion may be made with a puff duster equipped with a small, short metal nozzle which is forced under the cap before delivering the dust. Pollination Cucumber fruit set is particularly dependent on bees. Two kinds of flowers are borne on every cucumber plant — the male flowers, which supply the pollen, and the female ones, which produce the cucumbers. The two types of blossoms can be readily dis- tinguished, as the female flower is on the outer end of the little cucumber. In general, male flowers appear in great abundance in advance of the female flowers. This often leads to the erroneous notion that the cucumbers are failing to set fruit. Later the female flowers appear and the fruit is formed. In cool weather the ratio of male to female flowers is usually quite high. As the temperature rises, more female flowers are produced and the ratio is more nearly even, although there are always several times as many male as female flowers. Pollination, which results in the setting of fruit on cucumber vines, is dependent particularly on bees. Without proper pol- lination the cucumbers are deformed, or at least a high percentage of nubbins may be produced. In localities where bees are scarce it is advisable to place a few stands of bees in or near the field. Diseases How to recognize and control the diseases most common to cucumbers in California. Powdery mildew Powdery mildew occasionally causes damage to cucumbers. The disease is recognized by the presence of the fungus Erysiphe cichoracearum upon the leaves. Tiny patches of white growth first appear on the stems and older leaves, particu- larly at the crown of the plant. Although the) are more numerous on the shaded portions of the stems and the undersides of the basal leaves, they soon appear on both surfaces of leaves and on all parts of the plant. The spots enlarge and coalesce, covering the affected areas with a powdery growth. Affected leaves turn yellowish-green or yellow, later wilting, drying, and falling off. Severely diseased plants die premature!). [10 1 The organism overwinters on melon vines and other cucurbits that are grown throughout the winter months in the warmer regions. A 1 per cent Karathane dust, applied at the rate of 40 pounds per acre at 10-day to 2-week intervals, has given good con- trol of this disease. Southern blight This disease is caused by the soil-borne fungus Sclerotium rolfsii. The occur- rence and destructiveness of this disease are variable and sporadic, depending principally on weather conditions and previous cropping history. It is most damaging under warm temperature con- ditions in fields where very susceptible crops, such as sugar beets, have been severely attacked. Southern blight is usually first de- tected as a wilting of the growing tip during the middle of the day. In more advanced cases the whole plant wilts and dies because the stem tissue has rotted at the ground line. When such a plant is found wilted in the field, it is well to examine the main root near the soil sur- face. There the fungus causing the death of the plant can be readily seen and identified by the presence of white my- celium and the small, brown sclerotia, which look like mustard seed, clustered on the stem at the soil line. The sclerotia are scattered when the soil is tilled, and they are also distributed by running water. They germinate in a moist at- mosphere and infect other plants. Cu- cumbers should not follow crops that have been infected by the fungus. Angular leafspot This disease may cause damage to cu- cumbers growing in humid areas. In Cali- fornia, therefore, it is important only in the coastal areas, and it is most likely to cause severe damage if plants are sprinkler-irrigated. The first symptoms on leaves, stems, and fruits are small, water-soaked spots that later may become covered with a gummy or shiny bacterial exudate. The spots in the leaves become tan or brown; they are angular because the infected areas are delimited by veins. The bacterium (Pseudomonas lach- rymans) that causes this disease is seed- borne and persists on infected crop refuse. It is spread by water and infects through stomata. The use of clean seed, grown in arid regions where the disease is not likely to occur, and rotation to avoid fields that contain infected debris from a previous crop are effective methods of control. Cottony leak The fungus species, Pythium and Phy- tophthora, that cause this disease are soil inhabitants. The disease causes great- est damage in wet soils. The fungi are propagated by mycelium and by spores that move about in water. The fungus is spread by contact and can apparently penetrate the fruits without the aid of visible wounds. Plants or fruits that come in contact with infected soil or irrigation water, or that become spattered with wet soil containing spores or mycelium, mav become infected. THESE TERMS MAY BE UN- FAMILIAR TO YOU: The mass of interwoven threads of the fungus composing the my- celium often has a cobwebby or cottony appearance. The sclerotium is a compacted mass of mycelium. The sclerotium of some fungi is crustlike; others form sclerotia that look like seed. The stomata of leaves are microscopic openings, most abun- dant on the underside, through which the plant may be said to "breathe." [11] Infection takes place in the field, al- though decay may not develop until the cucumbers are in transit when it may spread very rapidly- During excessively wet seasons the fungus may also cause damping-ofl and vine canker. The first symptoms on the fruits are soft, dark-green, water-soaked lesions; later, as the mycelium penetrates the tis- sues of the fruit, water is liberated in large quantities. In the moderately humid atmosphere of containers during transit, a very luxuriant, white, cottony mycelium is produced, which sometimes completely covers the fruit. When juice from decay- ing cucumbers leaks down on those be- low, the mycelium becomes flattened and forms a matted layer on the surface of the fruits. Unless other contaminating organisms are present, the cucumbers will decay completely without disagree- able odor. This disease may be controlled in or- dinary seasons by providing good drain- age and by thinning out the plants. Cucumbers showing any evidence of de- cay at time of harvest should not be shipped. UP-TO-DATE CONTROL MEASURES At the time this manual went to press, the recommendations given here for the control of both diseases and insect pests were the most satis- factory that had been developed. These measures may continue to be the most effective for some time; however, chemical advances in this field are being made so rapidly that improved materials or methods might soon be available. To take advantage of the latest develop- ments and give your crop the best possible protection, consult your local University of California Farm Advisor before planning your pro- gram of disease and pest control. Damping-off Damping-off of cucumber seedlings is characterized by a shriveling and water- soaking of stems at the ground line that cause a sudden collapse and death of the young plants. In many cases it is often responsible for poor stands. This trouble may be caused by several fungi that are common in the soil and are most severe during periods of cool, wet weather. Damping-off can usually be satisfac- torily controlled by treating the seed with Spergon or Arasan. Spergon should be used at the rate of % teaspoon of dust per pound of seed or 4 ounces per 100 pounds of seed. The recommended rate for Arasan is % teaspoon per pound or 2 ounces per 100 pounds of seed. Mosaic Cucumbers are susceptible to several viruses, but the most prevalent and dam- aging virus disease is mosaic, which is caused by various strains of cucumber mosaic virus 1. This virus is world-wide in distribution and also infects many other cultivated crops and weeds. The symptoms in cucumber are quite variable because of the many strains of the virus, but the usual symptoms are stunting of the plant accompanied by mottling, cupping, and distortion of the leaves. Fruits produced on infected plants often show knotty or warty islands of green on an otherwise white background, a symptom that has been called "white pickle." The cucumber mosaic virus is trans- mitted from plant to plant by several species of aphids. The virus overwinters in winter-hardy host plants, such as spin- ach, celery, and beets, or in several sus- ceptible weed hosts. These infected plants are fed upon by aphids that later feed on healthy cucumber plants, thus introduc- ing the virus into the new crop. Simihu l\ . these insects spread the virus from plant to plant during the growing season. The most promising method of control is the development of resistant varieties. I 121 Insect Pests Those to watch for are described below with suggested control measures. Cucumbers are often attacked by in- sects or other related pests at practically every stage of growth. For this reason it is necessary for growers to control one or more of these pests in most of the growing areas of California. Pest control should ordinarily begin with treatment of the seed before plant- ing, and it may continue to harvest time depending upon the severity of the pests in different areas and their abundance at particular times of the year. Seed-corn maggot The white, wedge-shaped, legless larvae of this fly, Hylemya cilicrura (Rond.), often attack the germinating seeds and young seedlings, causing death or dis- figurement of the plants. Attacks are more prevalent in early plantings when germination is retarded and the soil is moist. Disking under green crops or ex- cessive amounts of organic materials tends to increase the maggot population. The adult flies select newly cultivated soil in which to deposit their eggs. Seed treatment before planting is usu- ally quite effective in reducing damage. One ounce of actual lindane, heptachlor, aldrin, or dieldrin, combined with an adequate fungicide, is enough to treat 100 pounds of seed. The fungicide should always be applied simultaneously with the insecticide. Insecticides are best ap- plied to the seeds as slurries rather than dusts, as dusts often come off in subse- quent handling of the seed. Wettable powders containing 50 to 75 per cent active insecticides are available. Seeds should be treated as close to planting as possible in order to reduce possible dam- age from long storage periods. Wireworms Wireworms, the active, feeding larvae of click beetles, bore into germinating seeds and young seedlings. They are com- monly % to 1 inch long, elongate, smooth, and glossy brown. Many species of click beetles spend several years in the soil as wireworms before changing into adults. Our economic species belong to the irrigated-land wireworms of the genus Limonius. Control can be accomplished in two ways: 1) soil treatment before planting; 2) seed treatment at time of planting. For soil treatment the following mate- rials can be used: DDT, 10-20 pounds actual per acre; aldrin and heptachlor, 3-5 pounds actual per acre; chlordane, 8-10 pounds actual per acre. These chem- icals are sprayed or dusted on the surface of the soil and disked to a depth of 6 inches the same day they are applied. DDT should be applied at least three months ahead of planting; the other chemicals can ordinarily be applied just ahead of planting as they kill worms more rapidly. The higher rates are sug- gested for heavy soils. Seed treatment with the materials listed for the seed-corn maggot is usually satisfactory. Cucumber beetles Cucumber beetles are often important pests of cucumbers and other cucurbits. The important species are the western spotted cucumber beetle. Diabrotica un- deimpunctata Mann., and the western striped cucumber beetle, Acalymma tri- vittata (Mann.). In southern California Diabrotica balteata Lee. and D. undeim- punctata howardi Barber also occur. [13] Left: the striped cucumber beetle and (center) the spotted cucumber beetle may cause damage or even kill plants. The squash bug (shown at right) only occasionally attacks The adult beetles are yellowish to yel- lowish-green with black spots or stripes and are Vs to ^4 inch long. They lay their eggs in the ground about the bases of the plants. Here the eggs hatch into larvae which feed on the roots and underground portions of the stems. The white to tan- nish larvae attain a length of V2 to % inch. A conspicuous brown anal plate, a dark head, and a dark shield just behind the head distinguish them from other larvae found about cucumber roots. The winter is spent in the adult stage, and about three generations occur a year. Damage is twofold. Adults feed on the foliage and stems of the young plants, and on the foliage, flower structures, and fruit of the larger plants. Damage may result in stunted or deformed plants, scarred fruits, or the death of small plants. Damage is also caused by larvae feeding on the underground portions of the plants; this often results in wilting, lack of fruit set, or the death of small plants. Several insecticide dusts can be applied to the plants when excessive numbers of beetles appear: DDT, 5 per cent dust at 20 pounds per acre. Do not use more than this, and do not use within three weeks of harvest. Tolerance 7 ppm (parts per million). Methoxychlor, 5 per cent dust at 30 pounds per acre. Can be used up to seven days of harvest. Tolerance 14 ppm. Cryolite, 40 per cent dust at 30 pounds per acre. Do not use within four weeks of harvest, or remove excessive residues by washing or brushing. Tolerance 7 ppm (fluorine) . Parathion, 2 per cent dust at 30 pounds per acre. Apply up to two weeks before harvest. Tolerance 1 ppm. Malathion, 5 per cent dust, at 20 to 30 pounds per acre. Apply to within three days of harvest. Tolerance 8 ppm. Melon Aphid The melon aphid, Aphis gossypii Glover, is the most common aphid on cucumber and may cause severe damage. This yellowish-to-greenish or greenish- black aphid is y^ C) inch long. It prefers the undersides of the leaves where it is found in colonies. Aphids spend the winter on a number of available hosts and in the spring fly to the young cucumbers, giving birth to [14] cucumbers— it prefers squash and pumpkins and rarely requires control in cucumbers. living young. The sexual stage is not always needed, and colonies develop very rapidly. Melon aphids suck the cell sap and cause distorting, stunting, and leaf curl- ing in addition to spreading cucumber mosaics. They also secrete honeydew. which enables a sooty mold to develop. Chemical control is often necessary, although ladybird beetles and syrphid fly larvae often assist greatly in reducing the aphid population. Materials such as DDT may increase the aphid problem, so populations must be carefully watched. The following chemicals can be applied for aphid control: Parathion. 2 per cent dust at 30 pounds per acre. (In San Diego County, however, a 1 per cent dust at the same rate has been found effective. ) Apply to within two weeks of harvest. Tolerance 1 ppm. Malathion, 5 per cent dust at 20 to 30 pounds per acre. Apply to within three days of harvest. Tolerance 8 ppm. Nicotine, 3.6 per cent nicotine alka- loid, 30 to 35 pounds per acre. Apply to within one week of harvest. Tolerance 2 ppm. TEPP, I per cent dust, 20 to 30 pounds per acre. Apply to within three days of harvest. Tolerance ppm. Spider mites Spider mites, Tetranychus spp., often damage cucumbers. These small, eight- legged pests are only % inch long, but they can pierce the cells on the underside of the leaves with their stylet-like mouth- parts, causing the foliage to yellow. They also web the leaves. Defoliation and loss of fruit may result. CAUTIONS ON INSECTICIDES The enactment of recent legislation dealing with residues of agricultural pesticides allowable in raw agricultural products makes it necessary for grow- ers to apply to cucumbers only chemi- cals for which established tolerances have been set. For this reason, check with your local agricultural authorities to see that your insect control program does not constitute a violation of the present law. For certain hazardous materials, at certain levels, it is neces- sary to post fields with "poison out" signs and obtain permits to conform to state and local laws. Most insecticides are poisonous and should be stored out of reach of chil- dren, irresponsible persons, or live- stock. Empty containers should be burned or buried. Certain chemicals, especially phosphates, such as para- thion, are particularly hazardous to the operator; protective clothing should be worn and equipment used as speci- fied by the manufacturer. All precau- tions, safety rules, and rates of appli- cation given on the label should be carefully followed. Although sulfur is commonly applied to cucumbers in coastal areas without injury, its use as a carrier in insecticide formulations in the hotter interior local- ities should be restricted, as foliage or fruit burn may occur. I "15] When mites appear, any of the follow- ing materials can be applied: Parathion, 2 per cent dust at 30 pounds per acre. Apply up to 15 days of harvest. Tolerance 1 ppm. Aramite, 3 per cent dust at 20-35 pounds per acre. Apply to within 15 days of harvest. Tolerance 1 ppm. Malathion. 5 per cent dust at 20-35 pounds per acre. Apply to within three days of harvest. Tolerance 8 ppm. Root-knot nematode These minute eelworms or nematodes, Meloidogyne spp., cause swellings or galls on the roots of cucumbers and many other plants. Aboveground effects are general lack of vigor, dwarfing of plants, and wilting in the middle of the day. Fumigating the soil before planting will usually control nematodes during the subsequent crop. D-D mixture and EDB (ethylene dibromide) are the two fumigants commonly used. Fumigants can be applied to the entire area, drilled in at 12-inch intervals by special equip- ment, or applied as row treatments in the area to be planted. For full coverage use 20 gallons (200 pounds) of D-D per acre at 12-inch spacings, or 3 to 4 gallons of actual EDB per acre. With 24-inch spacings, use 13V2 gallons (135 pounds) of D-D or 2.5 gallons actual EDB. An interval of 12 to 18 days should be allowed between treatment and planting depending on soil type, moisture, and climatic conditions. If a strong odor of fumigant persists, do not plant until the odor is reduced. Occasional pests The leaf hopper, Empoasca filamenta Delong, may become abundant enough to cause a yellow spotting of the leaves. Control is the same as for cucumber beetles. The squash bug prefers squash and pumpkins, and it attacks cucumber only occasionally. Control is seldom neces- sary. Thrips of several species may cause characteristic silvering of the young plants and sometimes deformation of the leaves. The plants usually grow out of the injury. If control is necessary, use the same materials given for cucumber beetles or melon aphid. Darkling ground beetles of the genus Blapstinus may cut off the small plants by feeding on the stems near the ground. Control is with DDT or other materials listed under cucumber beetles. Leaf miners of the genus Liriomyza may mine the leaves, causing character- istic serpentine tunnels. Control is usu- ally not needed; if necessary, leaf miners can be controlled by one to three appli- cations of 2 per cent parathion dust. Harvesting and Packing Picking and packing require considerable hand labor even when mechanical harvesting equipment is used. Harvesting Cucumbers should be picked at fre- quent Intervals to avoid losses due to oversize and overmature fruits. The fields arc; generally picked at 2- to 4-day intervals depending on the weather. Dark green fruits 5 to 8 inches long and l 1 /".' to 2 inches in diameter are the desired sizes for the fresh market. Cucumbers should be removed from the vines by turning the fruit parallel to the vine and giving it a quick snap. This I 16] pt* *V' , ^■*d>*w$ti* ."• ■ "^v ! •J *'x"fr-^;j|- £ -'7* ' -xN .*,V i JjC?l^*S$ / ** HAND PICKING * This may be done into buckets (as shown) or into baskets. Pickers empty their containers into bags or boxes at the ends of rows. prevents vine damage and results in a clean break of the stem. At each picking, culls and fruits that are odd-shaped or overmature are removed to insure con- tinued production of desired types. The culls are usually left in the field between the rows. The standard lug box is the container most commonly used in picking cucum- bers for fresh market. Wire carriers are fastened on the ends of the boxes to facilitate handling. Bushel baskets with wire or cloth-padded handles are also used. Pickling varieties are often picked directly into burlap sacks, or the fruit may be picked into metal buckets and then emptied into sacks before being taken to the processing plants. Although cucumbers must be hand- picked, a machine that will carry ten or twelve pickers over as many rows has been developed and is becoming popular. Lying across the long carrier, the pickers remove cucumbers of the desired sizes and place them on a conveyor belt that carries them to burlap sacks in a common grain-sacker arrangement. The machine cuts harvesting costs in half compared with the lug- or pail-picking method. It may increase yields 10 or 15 per cent over other picking methods. In addition, use of the machine results in less damage from trampling of the vines and thus prolongs the life of the plants. At the closer spacings two rows are generally trained together and can be harvested by one picker. At the wider row spacings only limited vine training is necessary, and one picker harvests a single row. Cloth or rubber gloves are often worn by the pickers to avoid hand injury from the spiny leaves, stems, and fruits. [17] MACHINE PICKING COMING Two views of the same machine. Here the cucum- bers are delivered to sacks on the rear of the machine. A worker standing in the back removes obviously bad pickles as they travel up the ramp. and GOING Si- IN BOXES This machine delivers the cucumbers into big boxes, supplies of which are kept at either end of the field. The boxes are made so that they can be handled by a fork lift for ease in getting them aboard a truck and to the collecting point. Packing After picking, the cucumbers are trans- ported to a field or central packing shed. Here trained workers wash, sort, and pack the fruits according to size and grade. When the fruits are washed, wax is often applied to improve appearance and keeping quality. The lug box is the container most com- monly used to pack and ship cucumbers to market. A small lug box. called a flat, is also used. For a fancy pack, especially early in the season, a shallow box hold- ing a single layer of fruit may be used. In this type of container 25 to 28 medium- sized fancy cucumbers are packed at an angle. The two-layer flat is also often used. Burlap sacks are usually used to trans- port pickling cucumbers from the field to the processing plant where they are gen- erally graded according to size. FRESH MARKET Here are two com- monly used packs for cucumbers sold in the fresh market. GRADING PICKLES This machine sorts pickles into grade sizes through different sized mesh, delivers them into boxes on both sides. If: f WmmSi Storage and transit Since cucumbers are a warm-season vegetable crop and are not frost-hardy, they are subject to physiological injury when exposed to temperatures below 50° F for prolonged periods. This response is referred to as chilling injury or low- temperature injury. Symptoms of chilling injury are sunken circular pits which may coalesce to form irregular sunken areas on the surface of the fruit, resulting in un- sightly appearance and increased suscep- tibility to decay. At temperatures below 50° F fruit is subject to injury both in storage and in transit, the degree of in- jury depending on the temperature and the length of the storage period. Injury may or may not be apparent at the time of removal from storage, and the length of time the cucumbers are held after they have been removed from storage influ- ences symptom development. Suitable temperatures for storage, handling, and transit depend on the dura- tion of storage and the use to be made of the product. If cucumbers are held no longer than two days, temperature has little practical effect. For longer periods in transcontinental shipment or in ware- house storage, temperatures should be kept near 50° F to prevent breakdown from chilling during subsequent market- ing. If the cucumbers are to be used im- mediately after removal from storage and the holding period does not exceed 16 days, temperatures somewhat below 50° F seem to have little practical in- jurious effect. For maximum storage life, however, cucumbers should be held at or near 50° F. even though they are to be consumed immediately upon removal from storage. PRODUCTION COSTS The cucumber is one of the more expensive crops to grow and har- vest. Many factors contribute to high production costs: the high cost of good soil in frost-free areas; prepa- ration of the land, including fumiga- tion, fertilizers, growing and putting out transplants, hand planting, re- planting, double capping, frequent weeding, and irrigation; frequent picking; the number of containers needed to handle the bulky fruits; and packing. Actual costs of growing and har- vesting a cucumber crop vary from locality to locality depending on local practices and the purpose for which the crop is grown. No single estimate of costs would be appli- cable to every grower. However, the summary of cost studies pre- sented in the accompanying table will indicate the items that must be considered and the relative costs for materials and the different operations. 20 Some Figures on the Cost of Producing Cucumbers Processing in San Diego County* for Market and Market Summer processing crop Early spring crop Summer and fall crop 17 4 tons 17 4 tons 15.6 tons Cost per acre ^So iff Cost per acre Cost per 100 lbs. Cost per acre Cost per 100 lbs. Land preparation : plow, disk, level, fumigate . Planting $20.00 $0.06 81.00 0.23 221.00 0.63 385.00 1.10 732.50 2.09 99.99 0.28 $ 46.28 9.10 136.17 327.74 411.34 82.37 49.40 $0.14 0.03 0.40 0.95 1.19 0.24 0.14 $ 12.25 2.33 92.10 347.43 123.97 42.60 40.00 $0.04 0.01 0.30 1.11 0.40 0.14 0.13 Cultural labor Harvest, packing Cost of materials Cash overhead . . . Land cost 42.00 $1,581.49 0.12 $4.51 Total costs f $1,062.40 $3.09 $ 660.68 $2.13 Based on survey records from 11 growers in San D fAmounts in breakdown are given in round numbers iego County. Production was fairly steady in California from 1952—1956 Crop Acreage Average yield Total Unit Total harvested per acre* production price value acres dollars dollars For pickles 1952 3,570 8.4 tons 30,000 tons 52.05 1,562,000 1953 4,000 8.6 tons 34,560 tons 52.10 1,800,000 1954 3,100 9.5 tons 29,470 tons 45.85 1,351,000 1955 3,100 341 bu. 1,057,000 bu. 1.30 1,374,000 1956 3,600 406 bu. 1,462,000 bu. 1.30 1,901,000 Early market 1952 1,500 420 bu. 630,000 bu. 2.10 1,323,000 1953 1,400 390 bu. 546,000 bu. 2.90 1,583,000 1954 1,600 420 bu. 672,000 bu. 2.00 1,344,000 1955 1,500 185 cwt. 278,000 cwt. 4.00 1,374,000 1956 1,500 185 cwt. 278,000 cwt. 4.75 1,901,000 Late market 1952 1,200 370 bu. 444,000 bu. 1.50 666,000 1953 1,700 330 bu. 561,000 bu. 1.45 813,000 1954 1,500 350 bu. 525,000 bu. 1.95 1,024,000 1955 1,500 185 cwt. 278,000 cwt. 3.80 1,056,000 1956 1,500 175 cwt. 262,000 cwt. 3.90 1,022,000 The weight of a bushel of cucumbers is 48 lbs. [21] In order that the information in our publications may be more intelligible it is sometimes necessary to use trade names of products or 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. ACKNOWLEDGMENTS The authors wish to express their appreciation to Raymond G. Grogan for the section on diseases, to W. H. Lange, Jr., for the section on insect pests, and to W. A. Harvey for information on chemical weed control. Co-operative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture co-operating Distributed in furtherance of the Acts of Congress of May 8, and June 30, If 14. George B Alcorn, Director, California Agricultural Extension Service. 7 £m-l,'68 (07767) BEB u THIS BOOK IS DUE ON THE LAST DATE COMPETITION, of a sort You may never see these cucumbers at a State or County fair. But by careful testing, analyzing, comparing of varieties, scientists from the Agricultural Experiment Sta- tion and Extension Service are gaining and distributing information valuable to farmers and processors. The photo above shows results of some field tests on cu- cumber varieties. To obtain additional copies of this manual or a catalog listing other manuals and free pub- lications available, see your University of California Farm Advisor (offices located in most California counties), or write to: Agricultural Publications 22 Giannini Hall, University of California Berkeley 4, California Orders for 10 or more copies of any one manual take a 20 per cent discount off the list price. All manuals are shipped prepaid. When ordering manuals, send orders and payment to the address above. Make checks or money orders payable to The Regents of the University of California.