Taking an environmentally sensitive approach to pest management


Missouri Environment & Garden



AUTHOR

David Trinklein
University of Missouri
Division of Plant Sciences
(573) 882-9631
trinkleind@missouri.edu

Squash: Recognition at Last

David Trinklein
University of Missouri
(573) 882-9631
trinkleind@missouri.edu

Published: May 1, 2010

Ask any number of people what their favorite vegetable might be and I doubt that many would answer “squash”. Disliked by many and eschewed by most, squash finally is getting the recognition it deserves in that the National Garden Bureau has chosen it as its 2010 ‘Vegetable of the Year’. A native American, squash comes in several forms all of which perform well under Missouri conditions. Squash is rich in vitamins, minerals and dietary fiber and low in calories making it a perfect choice for healthful eating. May is an ideal month to start squash in the family garden.

Research has shown that squash is native to both North and South America and has been used as a source of food for many millennia. Early European explorers to the Americas are credited with introducing squash to Europe sometime during the 16th century. Europeans were less than enamored by the taste of the new vegetable and negatively referred to it as “Naple’s or Spain’s revenge.” Considering it to be rather bland, the early colonists did not favor squash and it took quite some time for them to acquire a taste for it. Meanwhile, they tried to find other uses for this easily-grown vegetable including, in one case, using its seeds to remove freckles.

There are two basic groups of squash: summer squash and winter squash. Both are members of the Curcurbitaceae family making them closely akin to cucumber, gourds, musk melons and watermelon. Summer squash primarily are members of the species Curcurbita pepo and are consumed when the fruit is still immature and its rind soft. Many of the summer squash exhibit a bush type of growth. Winter squash can be found both in the species Curcurbita maxima and Curcurbita moschata and are not harvested until the fruits have fully matured and develop a hard rind. They store quite well and can be used throughout the winter–hence the name “winter squash”. Most winter squash exhibit a vining type of growth habit and occupy a considerable amount of space in the garden although plant breeders have developed a few bush-type cultivars. Confusion often exists between what is a squash and what is a pumpkin. The fact is that pumpkin is somewhat of a generic term and can actually refer to member of any of the three species mentioned above.

Squash prefers warm temperatures and should not be planted until the soil has warmed in the spring. They prefer a loose, well-drained soil and do poorly in heavy, clay-type soils. The latter can be made more acceptable to squash and most other garden vegetables though the incorporation of copious amounts of well-decomposed organic matter such as leaf mold or compost. Seeds should be planted about one inch deep and about 24 inches apart, depending upon cultivar and growth habit. Squash require at least six hours of direct sun each day in order to thrive and appreciate a site with good air circulation as well. The latter helps to prevent rots which tend to be problematic in periods of wet weather. Squash benefit from the application of a balanced fertilizer early in the year and again as fruits begin to add size. Supplemental irrigation during periods of hot, dry weather also is recommended.

If humans were slow to accept squash as a food source, insects certainly were not and squash is plagued by three major insect pests. These include the squash bug, the squash vine borer and the striped cucumber beetle. The squash vine borer is the least obvious and most damaging of the three. Typically plants will suddenly wilt and die for no apparent reason and usually at the time when fruit are first ready to harvest. The wilting is due to the action of the larvae of the squash vine borer. The adult borer (a moth) deposits its eggs at the base of the plant just at the soil line. Upon hatching from the eggs, the larva tunnel into the stem of the plant and live inside, consuming plant tissue as they develop. The appearance of a “sawdustlike” material at the base of the plant is strong evidence that infestation has occurred. When infestation is severe, plants wilt and die because the vascular (water conducting) tissue has been destroyed. To prevent borer damage, insecticides must be applied at the base of the plant before the larva enter the stem. Once inside, insecticides are of little control value. Some gardeners have reported successful control by wrapping the base of the plant with aluminum foil. This either confuses the adult or prevents larva from entering the stem after the eggs hatch.

Squash bug and striped cucumber beetle can be controlled through more conventional means. Squash bugs usually frequent the under sides of leaves and may go unnoticed until populations have built up to very large levels. Hand removal of egg clusters which appear shiny and look somewhat metallic is a good first step. Insecticides as sprays or dusts can also be used. Striped cucumber beetle is more noticeable than is the squash bug and usually less damaging. Many of the common garden insecticides that are stomach poisons are quite effective in their control.

Squash are subject to diseases common to vining crops including anthracnose, bacterial wilt, mildew (downy and powdery) mosaic virus and scab. Good sanitation practices and rotational planting can help reduce disease severity as can wide spacing of plants to improve air circulation. Fungicides are available to control many of the above but adequate coverage when spraying is somewhat of a challenge because of the dense nature of squash’s growth habit. Newer cultivars can be found with genetic resistance to certain squash diseases and they warrant a trial.

Frequently, the first fruit of squash (especially summer squash) turn black at the tips and die before attaining a useable size. This usually is due to poor pollination because of cool, damp weather and a lack of insect pollinator activity. Squash are monoecious plants meaning they bear both male and female flowers on the same plant and pollen must be transferred from male to female flower by an insect (usually a honey bee) in order for fruit to properly develop.

Harvesting of summer squash is especially critical since they are most palatable when immature. While older, more mature fruit is still edible summer squash is considered at its best when the fruit has enlarged but the rind can still easily can be penetrated with the nail of one’s thumb. This usually is when the fruit is between four and six inches long in the case of zucchini and six to eight inches long in the case of crooknecks or straightnecks. Patty pans should be picked when they are about three to five inches in diameter. Winter quash are harvested after the rind has turned a deep, solid color and is thoroughly hardened. In Missouri this usually does not occur until September or October.

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REVISED: December 5, 2011