Nutrient Needs

While cucurbit crops do moderately well on most fertile soils, they benefit greatly from a generous supply of organic material in the form of green and animal manures. Well-composted animal manures worked into the soil and concentrated in the area where the seed is expected to be planted (hills) is the most efficient means of using these materials. In addition to manures, applying mineral fertilizers is usually needed for a satisfactory crop. Fertilizers act as a supplement to the manure and provide an added source of plant nutrients during the growing season.

It is difficult to be specific about fertilizer recommendations because of great variation in soil types, soil fertility, and other soil conditions. In general, cucurbit crops can be expected to respond to a complete fertilizer containing 4 to 6 pct nitrogen, 8 to 10 pct phosphoric acid, and 5 to 10 pct potash.

This translates into 1 to 2 tablespoons for each hill prior to planting. In light, sandy soils, that leach readily, one or two side dressings of ammonium sulphate may be needed during the season; perhaps a tablespoon per hill will suffice.

In the garden, cucurbit crops are normally planted in hills, specific spacing depending upon the crop. In commercial practice, however, cucumbers, muskmelons, bush squash, and watermelons are drilled in continuous rows, and thinned to stand.

Cucurbit seeds are relatively large, and should be covered to a depth of 1 to 3 inches. After covering, the soil is lightly tamped, but not so firmly as to create a crust. In light, sandy soils that tend to dry out rapidly, seeds should be planted at greater depth than in heavier soils.

Assuming normal germination (80 to 90 pct), 4 to 5 seeds are planted in each hill. Thin the seedlings when they have 2 to 3 leaves. Remove all but 1 or 2 large, healthy, well-spaced plants per hill. More than 2 plants per hill causes undesirable crowding, and competition for nutrients, water and light. Under such conditions, the final result is unthrifty plants and declining yields.

Irrigation. In the West and Southwest, cucurbit crops are totally dependent upon irrigation as a source of moisture, and even in the Midwest and East some form of supplementary irrigation may be desirable during drought periods. The cucurbits are moderately deep-rooted crops, filling the soil mass to a depth of three feet or more. This means the soil must be supplied with enough moisture to maintain a thoroughly moist condition to this depth.

Furrow irrigation is probably the most practical for home gardens, especially after the young plants have a dozen or more true leaves. Moisture on the leaves from whatever source encourages several foliar diseases difficult to suppress with fungicides. Hence, sprinkler irrigation is not recommended if alternative methods are available.

Mulching and weed control are not critical for growing cucurbits in the home garden. If the soil directly above the seed (the hills) is kept from crusting, no mulch is needed. A thick, hard crust will prevent emergence of the young seedlings. Therefore, after planting and firming, it is important to scatter a thin layer of loose soil over seed in the hill.

There is really no safe, effective chemical weed control for cucurbit crops. If planting is done in a well-prepared seed bed, weeds will seldom be a problem and can easily be controlled by hand or by hoe. The cucurbits are leafy, rapidly growing, vigorous plants. Consequently, as they grow older they tend to shade out competition from weeds. Usually weeds are not much of a problem until late in the season, but by this time the crop is mature and little harm will be done.

The cucurbits are subject to infection by several diseases and attack by insects that can damage or even destroy a potentially promising crop without much warning and within a short time period. Nearly all the important pests are destructive to cucurbits you are likely to plant in the home garden. There are exceptions, however, such as scab, a fungus damaging only to cucumbers, and anthracnose, also a fungus, commonly attacking only watermelon. Squash bug and squash vine borer are more of a problem on squashes and pumpkins than with other cucurbits.

Cucumber Beetles

Bacteria responsible for bacterial wilt are spread by cucumber beetles. This fact is the key to control. If the beetles are eliminated or reduced to low levels in the garden, bacterial wilt will not be a problem. The bacteria multiply rapidly and plug the water transportation system of the plant. This results in characteristic wilting of the vegetative parts. Older plants at first may have only one shoot affected, but later the entire plant will wilt and die. Younger plants die quickly. It helps to promptly remove infected plants from the garden.

Anthracnose, a disease of watermelon, flourishes in warm, moist weather, and is particularly troublesome in the Southeast. Under favorable conditions it also attacks cucumbers and muskmelons, but is an acute hazard only to watermelon production. The symptoms are small, round, water-soaked spots on the fruits. These spots later become enlarged, sunken, with dark centers, which may turn pinkish in moist, humid weather. Infected leaves have a scorched appearance, and the stems may be girdled. Vines with the disease may die. The fruits are worthless, often decaying before they are mature.

A few simple preventive measures Often give satisfactory control if you are in an area where anthracnose is a problem. (a) Plant seed of varieties known to have a high level of resistance to the disease. (b) Plant seed that has been treated with a fungicide to remove spores of the fungus. (c) Practice garden sanitation, removing all the debris of cucurbit vines because the spores overwinter in this trash. (d) Select areas for planting that have not been used for cucurbit crops within the past 3 to 4 years.

Downy mildew fungus is a destructive disease of cucurbits, especially when meteorological conditions favor its rapid growth. Warm, moist conditions that occur at times during the growing season in the Atlantic and Gulf States are ideal for growth of downy mildew. However, low humidity, high temperatures and lack of free moisture on the leaves and stems immediately check the fungus growth.

Spores of the fungus are produced on the underside of the leaves, and are spread by wind or splashing of raindrops.

Initial symptoms are small, yellowish spots, with irregular edges which appear on the leaves at about the time the vines commence to set fruit. Tissue at the center of each spot soon turns brown and dies. Later the spots become more numerous, coalesce, and the leaf shrivels and dies. The brown or blackish withered leaves curl upward, a characteristic that makes downy mildew easy to identify with certainty. The fruits are not attacked, but fruits from denuded vines are apt to lack flavor, be tasteless, and are practically inedible.

Whenever possible use varieties with some tolerance or even resistance to the disease. Generally the home gardener will have to lean heavily on the use of a suitable fungicide.

Powdery mildew fungus can be a devastating pest of nearly all cucurbits, except watermelons. The first symptoms are small, white patches on undersides of the older leaves. As the disease increases in intensity, leaves and stems become covered with the white, powdery spore masses. The foliage gradually dies, leaving the fruit exposed to the sun. In muskmelons, such fruits ripen prematurely, and are usually sunburned and of poor quality.

The fungus responsible for powdery mildew requires much sunshine and reasonably high temperatures for best growth. Rains and low light intensity tend to check its rampant increase.