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Contents Foreword Origins, Classification and Uses Soils and Fertilizer Management Varieties and Culture Production on Plastic Mulch Squash and Cucumber Diseases Insect Management Weed Control in Cucumbers and Squash Sprayers Irrigation Good Agricultural Practices in the Harvest, Handling and Packaging of Fresh Market Squash and Cucumbers Marketing Cucumbers and Squash Production Costs Acknowledgments

Edited by William Terry Kelley

This publication is the result of a joint effort among the seven disciplines that make up the University of Georgia Extension Vegetable Team. It is the first and most comprehensive production guide ever assembled for squash and cucumbers in Georgia. The 12 topics covered in this bulletin are all integral parts of successful squash or cucumber management programs. Each topic focuses on a particular aspect of production and provides the latest management technology for that phase of production. The information in this publication is designed to help growers improve profitability in squash and cucumber production. Chemical pest control recommendations are subject to change from year to year and are not specifically mentioned in this publication. Growers are urged to consult the current Georgia Pest Management Handbook or check with their local county Extension agents regarding the most recent chemical recommendations. Mention of trade names in this publication is neither an endorsement of a particular product nor a lack of endorsement for similar unmentioned products.

ORIGINS, CLASSIFICATIONS AND USES
William Terry Kelley, Darbie M. Granberry and George E. Boyhan, Extension Horticulturists

Cucumbers and squash are both members of the cucurbit family, Cucurbitaceae. Many other vegetables belong to this family of vining crops: watermelon, muskmelon, pumpkin and gourd. They are all warm-season tender annuals. Generally, they have a spreading growth habit and have tendrils at the leaf axes. Botanically, the fruit is called a pepo — a type of fruit in which the ovary wall and receptacle tissue are fused to form a hard (or semi-hard) rind. Both cucumbers and squash have a long history of cultivation for human consumption, although they originated on separate sides of the globe.

Most squash produced in Georgia are summer squash, although smaller acreages of hardshell winter squash are produced in the state. The majority of cucumbers produced in Georgia are fresh-market slicing cucumbers. Some pickling cucumber production occurs in the state, although it remains a small portion of the total acreage. Although this publication focuses primarily on summer squash and slicing cucumber production, many of the practices described herein are also applicable to winter squash and pickling cucumber production.

Cucumbers, Cucumis sativus, are indigenous to an area of India between the Himalayas and the Bay of Bengal. One of the oldest cultivated vegetables, they were grown in western Asia as early as 1000 B.C. Cucumber is one of the plants specifically mentioned in the Bible. Cultivation migrated to Greece, Italy and China before arriving in Europe as early as the 9th century. Cultivation in England began around 1550. Columbus is known to have planted cucumbers in Haiti, and Native Americans were growing them in Florida by 1539. Early American colonists also planted cucumbers in Virginia by 1539, and the first permanent settlements in Massachusetts planted them in 1629.

Both the slicing and pickling varieties are members of the same species. Cucumbers are consumed as immature fruits. Slicing varieties are usually eaten raw in salads or as snacks. Pickled cucumbers are processed and used in numerous ways, including salad ingredients, relishes, sandwich slices and spears.

Slicing and pickling types of cucumbers can be differentiated primarily on the basis of the fruit appearance. Slicing types have long fruit, are generally dark green from stem to tip and have white spines that often are not visible. Pickling types are shorter and blockier and may have white or black spines. Fruit of pickling types are often dark green at the stem end and may be almost white at the blossom end.

Summer squash, Cucurbita pepo, has its origin in the areas of Mexico and Central America. Before Columbus’ arrival in the New World, summer squash were cultivated in much of what is now the southwestern, midwestern and eastern United States by Native Americans. Seafarers returned with the crop to Europe, where it quickly gained popularity.

Summer squash are consumed as immature fruit and can be cooked in numerous ways or eaten raw. Winter squash are generally consumed as mature fruit and are usually used for baking or in pies. Four common types of summer squash exist; all are produced in Georgia.

• Crookneck: Crookneck squash have slender, curved necks. Their surface is yellow and may become warty as they mature.
• Straightneck: Straightneck squash are similar in appearance to crooknecks except that, as the name implies, they have no curve in the neck, which is more slender than the base. These also may become warty as they approach maturity. Straightnecks are commercially popular because they pack more easily.
• Marrow: Generally, the only marrow type squash grown in Georgia is the zucchini squash. Zucchini are straight, elongated fruit with thin, smooth skins. They produce a whitish flesh with a green or gold skin. Most zucchini produced in Georgia are of the green skin type. Occasionally the Italian marrow, or cocozelle, is grown in Georgia. Fruit of this type squash are cylindrical, short and usually striped.
• Scallop: Scallop squash are flat or saucer-shaped with thickened waved edges. They may have a green or yellow skin but more commonly have a white skin.

Soil requirements and fertilizer management are similar for squash and cucumbers whether they are grown for fresh market or for processing. Both crops will perform well on most soil types found in Georgia. Neither crop can be grown in poorly drained areas. Both crops will produce good yields with proper management when grown on any fertile, well-drained soil. Medium-textured soils with enough organic matter to hold moisture and keep the soil loose for proper root growth are ideal for both squash and cucumbers. Coarse, sandy soils are preferred for early spring production because they tend to dry out and warm up more quickly. However, these soils also require more intense fertilizer and irrigation management.

Proper crop rotation is essential in squash and cucumbers to reduce potential problems from diseases, nematodes and herbicide carryover. Never grow squash or cucumbers on land that has been planted with any other cucurbit crop such as watermelons, cantaloupes, pumpkins, etc, within the last three years. Land planted with squash or cucumbers in the same time frame should also be avoided. Proper rotation with non-cucurbit crops will help prevent potential problems from carryover of disease organisms on plant material. Rotation with crops that discourage nematode increases is also beneficial. A good crop rotation program could include corn, rye or other small grains. Other well-fertilized vegetable crops not in the cucurbit family, such as fresh-market tomatoes or peppers, can be good crops to use in a squash or cucumber rotation. Residual fertilizer and organic matter help develop early growth.

Always be aware of any herbicide material that has been used in the last 12 to 18 months that might create a potential carryover problem on land intended for squash or cucumbers. Check labels of herbicides previously used for carryover restrictions.

Squash and cucumbers both produce moderately deep root systems. However, most of the roots are in the top 8 inches of soil. Therefore, plan soil preparation in order to produce good soil tilth to a depth of at least 8 inches. Work the soil when moisture is adequate, but avoid wet soils. Chop litter from previous crops and work it into the soil by disking prior to plowing to speed up breakdown of organic matter.

In Georgia, optimal yields for both crops have been obtained with deep turning to bury the litter at the bottom of the furrow. Smooth the soil with something other than a disk harrow, which can cause undesirable soil compaction. A tine harrow with a smoothing board or a Rototiller will do a nice job of smoothing the beds. Smoothing operations should be in the same direction as rows, leaving tire tracks exposed so that all future trips can be in the same tracks to prevent further compaction.

Both squash and cucumber can benefit from subsoiling, particularly if a hard pan is present in the field. This allows crop roots to obtain water and nutrients from a greater volume of soil. This can be particularly beneficial in drought situations. When planting on bare ground, it is advisable to plant on a bed raised at least 4 inches high and tapered to the edges to provide good surface drainage, enhance warming of the soil and reduce damage to vines during spraying. The seedbed should be firm and have a uniform texture before planting. When plastic mulch is to be used (see "Production on Plastic Mulch"), the ground should be tilled deeply enough to form a good bed and worked to minimize clods on heavier soils.

As with any vegetable production system, a recent soil test forms a basis for fertilizer and lime requirements. Check with you local county Extension office or crop consultant regarding proper procedures for soil sampling and interpretation of results. Take the soil test several months before crop establishment to determine lime requirements and to make necessary applications in a timely manner.

A pH of between 6.0 and 6.5 is best for squash and cucumber production. If soil tests reveal a need for lime, apply and disk in dolomitic lime at least three months before planting. Many nutrient deficiencies detected during the growing season, such as calcium or phosphorous deficiencies, can be traced to excessive soil acidity. Foliar applications often can overcome calcium deficiencies. Generally, phosphorous is in the soil but unavailable at low pH; this can be difficult to correct during the season.

Cucumbers and squash are fast-growing crops but are medium to light feeders of major nutrients. On Coastal Plain soils, nitrogen requirements for squash and cucumbers will range from 80 to 120 pounds per acre. On Piedmont, Mountain and Limestone Valley soils, 80 to 100 pounds of nitrogen per acre will be sufficient. Apply potassium and phosphorous based on soil test results. Table 1 summarizes the recommended potassium and phosphorous applications based on the soil test rating for each. For example, if a soil test revealed a low potassium rating and a medium phosphorous rating, 120 pounds of potassium and 80 pounds of phosphorous would be required.

Preplant fertilizer application rates will vary with the natural fertility and past history of the soil. If soil test magnesium is low and lime is recommended, apply dolomitic limestone. If magnesium tests low and lime is not recommended, apply 25 pounds of elemental magnesium per acre. Other nutrient elements also are essential for good crop growth and yield. Boron, sulfur and zinc can be applied in preplant fertilizer if soil tests reveal a need. Apply 1 pound of boron, 10 pounds of sulfur or 5 pounds of zinc per acre if needed. A complete fertilizer with minor elements will provide most other required nutrients. A fine line lies between adequate and toxic amounts of micronutrients. Apply them only when needed and in precise amounts. Watching for nutrient deficiencies is very important in times of high rainfall or frequent irrigation.

Correcting deficiencies of major nutrients is not feasible through foliar nutrient applications. Therefore, an adequately managed soil fertility program is required to maintain proper growth and development. Some deficiencies of minor elements can be remedially corrected through foliar applications. However, it is always best to supply adequate amounts of these nutrients via your basic soil fertility program.

Apply all phosphorous, micronutrients and 30 percent to 50 percent of nitrogen and potassium before planting. Because phosphorous is relatively immobile in the soil, it should be placed in close proximity to the rooting zone. For best results on bare ground, band base fertilizer applications 3 inches to the side and 3 inches below the seed level. If plastic mulch will be used, incorporate fertilizer into the bed before laying the plastic.

Sidedress squash with 30 pounds of nitrogen and 30 pounds of potassium per acre when plants are 8 to 10 inches high. Apply another 30 pounds after the first fruit flush is over to maintain production. For cucumbers, sidress with 30 pounds each of nitrogen and potassium per acre when vines begin to run. Additional nitrogen applications may be needed in areas of high rainfall or in areas where leaching may be a problem. When plastic mulch with drip irrigation is used, additional applications will be injected (see "Production on Plastic Mulch").

Over-the-top applications of dry fertilizer are potentially hazardous because particles may become lodged in the foliage and cause burns. If over-the-top applications become necessary, use less caustic materials such as sodium nitrate and irrigate immediately after application to reduce the chances of fertilizer burn. Always make these applications on dry foliage. All nitrogen fertilizer used for squash and cucumber fertilizer programs should contain at least 50 percent of the nitrogen in the nitrate form.

To reduce the chances of fertilizer burn, never apply more than 40 pounds of nitrogen or potassium to squash or cucumber at any one time. Also avoid overfertilizing cucurbits with nitrogen; excessive nitrogen can delay maturity, reduce fruit set and reduce shipping quality of fruit.

Plant tissue and petiole sap analyses are excellent tools in evaluating crop nutrient status. Periodic tissue analysis or sap tests can be used to determine if fertility levels are adequate or if supplemental fertilizer applications are needed. Both tests are useful in detecting nutrient deficiencies that may have developed during the growing season.

The most recently mature leaves of the crop are the subjects for plant tissue analysis. A sample of 20 to 30 leaves should be taken from the area(s) in question. Check with your local county Extension office or crop consultant on proper tissue analysis techniques and for location of analytical laboratories and interpretation of results.

Petiole sap analysis is a more recently developed method. Fresh sap pressed from leaf petioles is analyzed for nitrogen and potassium concentrations. Sap analysis kits are available from a number of sources. Tables 2 and 3 show critical ranges for nutrient concentrations in squash and cucumbers for tissue analysis and petiole sap analysis, respectively.

VARIETIES AND CULTURE
William Terry Kelley and George E. Boyhan, Extension Horticulturists

Both cucumbers and squash are warm-season crops that are sensitive to frost and cold injury. These short-season crops can grow at various times of the year in all areas of Georgia. In the warmer, longer season of South Georgia, two crops per year are common.

Because squash and cucumbers are warm-season crops, planting should be delayed until probability of frost is sufficiently low. Cucumber and squash plantings in South Georgia occur fairly early in the spring, with successively later plantings in the middle and northern sections of the state. Local frost and freeze data should be taken into account when selecting proper planting dates. Cucumbers and squash are almost exclusively direct seeded. Transplanting is not recommended.

Planting early yields little advantage because germination will be slowed by cool soils. In cool, wet soils, germination may be delayed and seeds may decay. Successive plantings can be made every 10 to 14 days for a continuous harvest. Always make the last planting at least 60 days before the first expected frost.

A variety of plant populations can be used for both crops. Cucumbers are generally planted in rows 36 inches apart with an in-row spacing of 9 to 12 inches. Bush type squash are usually planted in rows 36 inches apart with 12 to 18 inches between plants.

In recent years, the development of precision seeders has made more accurate planting feasible. This type of planter can save seed and reduce the need for thinning. If thinning is necessary, pinch the excess plants off at ground level rather than pulling them up, which disturbs the roots of other plants. Precision planters can often cut seed used per acre by 20 percent to 40 percent over traditional methods and eliminate the need for thinning. Precision seeding can greatly enhance uniformity in plant spacing and planting depth, which usually translates into more uniform production and harvest.

Always use quality treated seed from a reputable source. A windbreak of small grain strips placed periodically throughout the field will reduce sandblasting injury and mechanical damage (twisting, etc.) to young seedlings from spring winds.

Maturity dates for squash and cucumber will depend primarily on the variety and the environment. Temperature, soil type and moisture regime can have a significant impact on the number of days from planting to maturity. See Table 4 for a summary of planting and seeding recommendations.

Base variety selection of squash and cucumbers on criteria similar to that used for other vegetables. Obviously, yield is of primary concern to the grower; however, other factors such as horticultural characteristics, disease resistance and adaptability should also be considered. Varieties should produce a competitive yield compared with standard varieties currently produced. Quite often buyers will prefer certain varieties. Therefore, it is a good idea to check with the buyer for preferences before making your selection.

When selecting varieties, find out as much as you can about adaptability of particular varieties to see if they perform well in your area. If possible, consult local growers familiar with the variety regarding their experience. If using a new variety, consult your county Extension office for information regarding its performance in variety trials in your area. Well-adapted varieties will perform well over a wide range of environmental conditions.

Horticultural characteristics such as color, shape and skin texture are also important in variety selection. Summer squash should have a skin color and texture that is acceptable to the market. They should develop seed slowly and maintain a glossy appearance as they mature. Slicing cucumbers should be uniformly smooth and dark green. They should have small seeds that do not harden early, have a desirable flavor and have an appropriate length to diameter ratio.

Recent advances in squash varieties have resulted in varieties that are resistant to some viruses that affect squash (see "Squash and Cucumber Diseases"). Although these varieties may be resistant to certain viruses, they may not be resistant to all viruses present in your field. Therefore, a consistent oil spray program will still be necessary in seasons of high virus pressure. Also, because virus pressure is greater during summer and fall production, you may benefit from using resistant varieties for these plantings and the less expensive non-resistant varieties for early spring production.

Other disease resistance characteristics may also be present in some varieties. Cucumber varieties, in particular, often possess a number of resistance characteristics. Any time disease resistance combines with good yield and good horticultural quality, the variety is that much more appropriate if it is adaptable and acceptable to the market.

Fresh market cucumbers should be more attractive in appearance and have a darker green skin than pickling varieties. They are also longer than most pickling cucumbers. Average length/diameter ratio (LDR) is an important characteristic of cucumber varieties. The LDR varies according to growing conditions, environment and position on the vine. Fruit at the crown of the plant will have lower LDR than those at the more distal ends of the vines. Conditions favorable to growth will increase LDR. Average LDR for slicing cucumbers varies between 3.0 and 4.5.

New squash and cucumber varieties are developed and introduced yearly. Therefore, any list of varieties will soon be outdated as new varieties hit the market. Tables 5 and 6, however, list some of the varieties that have been popular in Georgia or have performed well in experimental trials.

Advances in plant breeding of cucumbers have resulted in varieties of cucumbers that exhibit various combinations of flower types. These fall into several groups that are explained below. Growers will need to be familiar with this terminology in selecting varieties and versed in the ramifications that environmental conditions have on the various types.

Gynoecious

All plant flowers are female. Only female flowers produce fruit, so these types increase the incidence of female flowers in the field. They must however, be interplanted with a male pollinator to produce fruit. Most gynoecious varieties are blended with a small percentage of pollinator seed by the seed company. Make sure that pollinators are present, because without them yields will be drastically reduced.

Predominantly Female

Plants are usually produced from crossing gynoecious and monoecious (see below) lines. These plants, as the name implies, generally produce mostly female flowers under normal conditions. Terminals and laterals of PF varieties usually produce continuous female flowers. Unstable varieties, cool temperatures and crowding of plants can increase the incidence of male flowers in these types.

Monoecious

Plants produce numerous male flowers and infrequent female flowers. These plants usually begin by producing only male flowers then go through a period of mixed flowering (producing both male and female flowers) and end with a period of only female flowers.

Hermaphroditic

Plants produce perfect flowers or flowers that have both male and female parts in the same flower. These are mostly experimental at this time.

The environment can have a marked influence on sex expression in cucumber and squash plants. Climatic conditions often radically change the ratio of male to female flowers. High temperatures and long days induce male flower development; low temperatures and short days cause predominantly female flower development. For this reason, early spring crops often produce numerous female flowers before the first male flowers. Almost any type of stress — light intensity, fertility, moisture, temperature, plant population, etc. — can result in more male flowers.

Because most squash and cucumber plants produce separate male and female flowers, pollen transfer from the male to the female flower is essential to the production of good yields of high quality fruit. Bees are the most common agent of pollination for cucurbit crops. Therefore, an ample supply of honeybees should be introduced into production fields to enhance and ensure pollination. Poorly pollinated fruit will be misshapen and have poor development, which usually results in unmarketable fruit.

Native honeybee populations have declined in recent years; although bumblebees are excellent pollinators, they are generally not plentiful enough to be effective. Therefore, recommendations for numbers of hives per acre have changed. As a general rule, you should place one hive of honeybees for every acre of squash and one to two hives for each acre of cucumbers.

Squash and cucumber flowers are generally open in the morning hours until early afternoon, which coincides with the hours that honeybees are most likely to be working. Schedule spraying and irrigation around these times to avoid disrupting pollination. Other important factors to consider in hive management include:

1. supplying a good clean source of water for bees;
2. grouping hives within 500 feet of one another, which increases competition so bees are more apt to forage further into the field;
3. removing competing sources of pollen near production fields;
4. placing hives in fields just before or just after the onset of blooming; and
5. avoiding pesticides with high toxicity to bees.

Bees often make several visits (7-10) to a flower to complete pollination. The use of chemical attractants is one option that many growers consider. Although these attractants may be of use in marginal situations, there is no substitute for a good supply of bees. For more information on pollination and bee maintenance, consult University of Georgia Cooperative Extension Service Bulletin 1106, Bee Pollination of Georgia Crop Plants.

Periods of cloudy, cool, windy or wet weather also can hinder bee activity. Some evidence shows that the application of 0.2 pounds of boron two or three times beginning at first bloom can enhance pollination in some cucurbits. These applications can be made in conjunction with regular spray programs and are most effective in boron deficient soils.

Cross-pollination of squash with other cucurbit crops is often a concern of growers. In most cases this is not a problem. However, plants of the same species will cross-pollinate and some cross-pollination occurs between some other species. By knowing the genus and species of the crops in question you can determine the potential for cross-pollination. Unless you are going to save seed from the crop, which is not recommended, cross-pollination will rarely be a problem for the commercial grower. However, these are the combinations that can cross-pollinate between species:

• Cucurbita maxima will cross with Cucurbita moschata.
• Cucurbita moschata will cross with Cucurbita pepo.
• Cucurbita pepo will cross with Cucurbita mixta.

PRODUCTION ON PLASTIC MULCH
Darbie M. Granberry, Extension Horticulturist

In Georgia, vegetable acreage on plastic has been increasing since the late 1980s. By 1994, approximately 10 percent of the total vegetable acreage in the state was grown with plastic mulch. This acreage was expected to continue increasing throughout the 1990s.

A production system using plastic mulch and drip irrigation, commonly referred to as "plasticulture," offers many benefits. However, the extent to which benefits are actually achieved depends on how effectively production is managed. Plasticulture has the potential for increasing profitability of many vegetable crops. On the other hand, poor management of crops on plastic usually results in greater losses (disasters) than poor management of production on bare ground.

Among other things, plastic mulch and drip irrigation:

1. enhance earliness during spring production,
2. increase yield and quality,
3. help control weeds,
4. improve irrigation efficiency by application of water directly to the root zone and
5. facilitate more effective fertilizer management by fertigation through the drip system.

Disadvantages can include increased costs of production and disposal of used plastic mulch.

In any given situation, the degree of earliness and increase in yield depends on the specific vegetable being grown; the average temperatures during the production season, especially in early spring; and soil productivity. However, on the average, vegetables grown on plastic mulch are ready for harvest one to two weeks earlier and frequently yield 50 percent to 100 percent more marketable product.

Because of larger size, fewer defects, reduced contamination with soil and increased shelf life, plasticulture improves the quality of most vegetables. However, environmental factors, especially rainfall and temperature; the severity of insect and disease problems; and soil characteristics affect the overall degree to which plastic improves quality.

Reducing weed pressure is an important advantage. Plastic mulches that block light transmittance — black, white-on-black and certain wavelength-selective plastic mulches — prevent germination or growth of most weeds except nutsedge. See "Weed Control in Cucumbers in Squash" in this bulletin.

Considerations for Producing Vegetables on Plastic

For technology to be a good investment, economics dictates it must increase profitability. Plastic mulch and drip irrigation can substantially increase production costs. Will you make more money by growing cucumbers or squash on plastic? That depends on how much it costs you to use the technology relative to the added income it generates. For current estimates of production costs and expected returns, see the "Production Costs" section of this publication.

The anticipated increased income from the use of plastic with some crops, especially high-value crops such as fresh-market tomato and pepper, readily justifies the costs of plastic mulch and drip irrigation. Plasticulture may or may not increase the value of low-value crops enough to justify its cost.

To help spread the costs of mulch and drip irrigation over several seasons or crops, multiple cropping on plastic (growing a second or even third crop immediately after the previous crop) has become a common practice. Proper installation of a good quality plastic mulch and drip tape is absolutely necessary for successful multiple cropping. Consult your county Extension agent or plastic mulch/irrigation dealer to ensure the materials you select will adequately meet your needs.

Processing cucumbers are not high-value products. The increase in their value when grown on plastic may not cover the cost of the plastic and drip tube. Except where processing cucumbers fit into double or triple cropping, in which a previous crop pays for the plastic and drip tube, growing them on plastic does not seem economically feasible.

Fresh-market cucumbers or squash can be profitably grown on plastic. They may be the only crop grown on the plastic or the first, second or third crop in a multicropping system. Cucumbers do well as a second or third crop behind a fall, early spring or summer crop. However, planting cucumber behind a late spring crop may reduce yields. Yields of cucumbers planted between early June and late July commonly are reduced because of heat stress. Squash may be planted on plastic from early spring until early fall. For fall production, cucumber and squash should be planted early enough to allow time for a sufficient number of harvests before frost.

For spring production, especially early spring, cucumber and squash should be planted on black plastic because it will warm the soil and enhance early growth. For production during summer and fall, these crops should be planted on white-on-black plastic to help prevent excessive heating of the plastic and soil when temperatures are high. If black plastic from a previous spring crop is to be used for summer or fall production, paint the top surface with a 2:1 dilute of white latex paint to water.

Cucumbers can be seeded in a single row on the mulched bed. However, if beds are on 4- to 6-foot centers and the top surface of the plastic mulched bed is at least 28 inches wide, yield potentials can be increased by planting two rows per bed. Where one row exists, preferably centered on the bed, a final stand of single plants 6 inches apart in the row is recommended. For two rows, preferably centered on the bed, the rows should be 12 to 16 inches apart with plants offset and spaced 8 to 10 inches apart in the row. Whether one row or two rows are planted to a bed, the drip tape should be located no more than 6 to 8 inches from the row(s).

Squash, both bush and vine types, should be planted in a single row, preferably centered on the mulched bed. For early spring plantings and for most cultivars, plants should be spaced 18 inches apart. Very vigorous cultivars, especially when grown during seasons conducive to maximum growth, should be spaced 24 inches apart.

In general, rows should be centered on the beds. However, when establishing a cucumber or squash crop on previously used plastic, ensuring that the drip tape is not damaged during planting/transplanting and that the location of the row or rows is such that the drip tape will effectively irrigate/fertigate plants takes priority over centering rows on the bed.

Cucumber or squash can be seeded or transplanted into the plastic mulch. Compared with seeding on plastic, transplanted cucumber or squash can usually be harvested about two weeks earlier. Will it pay you to invest in transplants? That depends on how much more value an earlier harvest adds to your crop.

Plastic mulch with drip irrigation is a relatively new technology for Georgia vegetable growers. It is more complicated and requires a much higher level of management than production on bare ground. Limited space in this publication does not permit coverage of all the information needed for successfully growing vegetable crops on plastic. However, University of Georgia Extension Bulletin 1108, Plasticulture for Commercial Vegetable Production, is available from your local county Extension office. Please refer to Bulletin 1108 for additional information. This bulletin covers the benefits of drip irrigation and fertigation in detail and thoroughly discusses effective management of plasticulture technology and how it affects crop growth and productivity.

SQUASH AND CUCUMBER DISEASES
David B. Langston, Jr., Extension Plant Pathologist

Squash and cucumber are subject to many diseases that cause serious losses throughout the state each year. Both crops share several common diseases; however, each has unique diseases affecting it. A clear understanding of the diseases and the disease management strategies are necessary for successful squash and cucumber production.

Alternaria Leaf Spot Alternaria leaf spot, caused by Alternaria spp., can cause serious damage under extended periods of wet weather. The occurrence of this disease in Georgia is sometimes sporadic but can be devastating if left unchecked.		Figure 1
Symptoms The disease causes tiny brown leaf spots, which enlarge and cause a target spot with concentric rings (Figure 1). Older lesions will develop a dark color in the concentric pattern. Spore production, which causes the dark color, can infect new sites if no protective measures are followed.	Disease Management Most fungicides used in disease management will suppress Alternaria leaf spot. No resistant cultivars are available.

Angular Leaf Spot Angular leaf spot, a bacterial disease caused by Pseudomonas lachrymans, attacks cucumber leaves, stems and fruit. The bacterium that causes angular leafspot overwinters on old plant debris and on cucumber seed. During rains it splashes from the soil to the stems, leaves and later to the fruit. Once infection takes place, the organism spreads over the field on the hands of workers or by cucumber beetles. Angular leafspot is most severe during extended rainy periods when temperatures are between 70º and 80ºF.		Figure 2
Symptoms Spots on the foliage are straw colored to light brown and angularly shaped (Figure 2). Affected areas first seem water soaked, then gradually dry and split. After the diseased tissue splits open, portions of it tear out, leaving irregularly shaped holes in the leaves. Small, circular spots develop on the fruit. These diseased areas later crack open and turn white.	Disease Management The primary disease prevention tool is disease-free seed. Angular leaf spot resistant cucumber varieties are available. A two-year rotation behind crops other than cucurbits and cultivating the soil when it is dry will decrease the ability of the bacterium to survive and infect upcoming cucumber crops. During warm, moist periods, when disease development is favorable, copper sprays may reduce the spread of the disease.

Anthracnose Anthracnose, caused by the fungus Colletotrichum lagenarium, attacks all above-ground parts of the cucumber plant. The fungus causing anthracnose overwinters locally on old cucurbit vines and may appear any time during the growing season. It may reach epidemic proportions when rainfall is above average and temperatures are between 70º and 80ºF.		Figure 3
Symptoms The first symptom of anthracnose is observed on the oldest leaves as round, reddish-brown spots. The centers of some spots fall out, giving the leaf a shot-hole appearance (Figure 3). Often the leaves at the center of the plant die first, leaving the crown of the plant bare. Light brown to black elongated streaks develop on stems and petioles. Round, sunken lesions may appear on the fruit. These lesions first appear water-soaked and then turn a dark green to brown. The pinkish ooze often noticed in the center of the lesion is a mass of spores of the fungus.	Disease Management A one-year rotation and deep turning infected debris immediately after harvest are effective cultural practices for reducing inoculum levels in subsequent crops. Using disease-free seed produced from areas not known to have anthracnose is an essential disease-prevention measure. Cucumber varieties resistant to anthracnose races 1, 2 and 3 are available. Several protectant fungicide options, which can be found in the Georgia Pest Management Handbook, are available.

Gummy Stem Blight Gummy stem blight, caused by Didymella bryoniae, attacks only the leaves and stems of cucumbers and is one of the most destructive diseases of cucumbers in the state. This disease is driven by cool, moist periods, especially extended periods of leaf wetness. The gummy stem blight fungus can easily be brought into a new area on or in the seed. Once the disease becomes established, it produces millions of sticky spores. These spores spread over the field as humans, other animals and machines move through wet vines.		Figure 4
Symptoms It is noticeable when an individual runner or an apparently healthy plant suddenly dies. Vine cankers are most common near the crown of the plant (Figure 4). This disease is usually identified by finding elongated, water-soaked areas on the stem. These areas become light brown cracks in the vine and usually produce a gummy ooze. On the older leaves, this disease may produce brown to black spots. It spreads from the center of the hill outward, as does anthracnose and downy mildew.	Disease Management Choosing high quality, disease-free seed and transplants should be the first line of defense in preventing losses to gummy stem blight. A two-year rotation with crops other than cucurbits is another appropriate disease-management tool. Protective fungicide sprays can offer the most effective disease suppression if applied in a timely manner. Consult the Georgia Pest Management Handbook for details concerning protective fungicides.

Target Spot Target spot, caused by the fungus Coryneospora cassiicola, can defoliate and destroy an entire crop if left unchecked. It occurs very sporadically and can be confused with downy mildew and other leaf spotting diseases.		Figure 5
Symptoms Target spot begins on leaves as yellow leaf flecks becoming angular with a definite outline (Figure 5). Later spots become circular with light brown centers surrounded by dark brown margins. Lesions join together and produce large dead areas with dead and shedding leaves.	Disease Management Most protective fungicides used to control other foliar pathogens will suppress target spot. Destroying infected debris or sanitizing greenhouse areas will greatly aid in reducing the spread of the disease. Several cucumber varieties have resistance to target spot and are the best assurance against severe disease losses when combined with sanitation and fungicide applications.

Bacterial Wilt The bacterium Erwinia tracheiphila causes bacterial wilt. The bacterium affects only cucurbits, except for watermelon, which is almost completely immune. The pathogen overwinters in the godies of the spotted and striped cucumber beetles. It then hibernates in the beetle’s digestive tract and in the spring finds its way through the feces of the carriers to the young plant. The bacterium enters the plant tissue only through deep wounds produced by beetles when feeding.		Figure 8
Symptoms The most typical symptom associated with bacterial wilt is individual runners or whole plants wilting and dying very quickly (Figure 8). Affected runners usually will turn dark green before becoming necrotic as the wilt becomes irreversible. Long strands of bacterial slime can be observed if wilted runners are cut and the cut ends are pressed together and then pulled apart.	Disease Management The most effective tool for managing bacterial wilt in cucumber is controlling the cucumber beetle. This can be achieved by using contact or soil applied insecticides. The use of resistant varieties is also recommended.

Diseases Affecting Both Cucumber and Squash