Taking an environmentally sensitive approach to pest management


David Trinklein
University of Missouri
Plant Science & Technology
(573) 882-9631

For the love of Squash

David Trinklein
University of Missouri
(573) 882-9631

May 21,2024

minute read

multi-colored squash

(Credit: Pixabay)

A versatile and nutritious vegetable with a rich history, squash has enchanted gardeners and gourmands for decades with its diversity in shape, color, and flavor. A native American, squash comes in several forms all of which perform well in the garden. Squash is rich in vitamins, minerals, and dietary fiber and low in calories making it a perfect choice for healthful eating. No doubt, its many virtues is what caused the National Garden Bureau to name squash the 'Vegetable of the Year' for 2024.

butternut squash cross-sections on grass

Squash is a nutritious vegetable filled with vitamins, minerals and dietary fiber. Pictured is butternut, a type of winter squash. (Credit: Pixabay)

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.

pile of zucchini

There are two main classifications of squash: summer and winter. Pictured is zucchini which is a very popular type of summer squash. (Credit: Pixabay)

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.

pile of pumpkins

The term "pumpkin" can refer to any member of three species of Cucurbita. The large light-colored squash in the rear of the picture is Curbita moshchata, commonly referred to as field pumpkin.

Squash requires at least six hours of direct sun each day in order to thrive and appreciates 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 benefits 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.

Squash prefers warm temperatures and should not be planted until the soil has warmed in the spring. It prefers a loose, well-drained soil and does poorly in heavy, clay-type soils. Poor soil 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.

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 deposits its eggs at the base of the plant just at the soil line.

wilted squash leaves

Gradual wilting followed by death of the plant is typical or squash viner borer attack or bacterial wilt infestation of squash. (Credit: University of Georgia)

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 "sawdust-like" 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 is 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 generous 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 straight necks. 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.

yellow squash

Several squash cultivars recently have been named All-American Selections award winners. Pictured is 'Sunburst' which is a patty pan type of squash. (Credit: Texas Master Gardener Association)

Popular types of squash include:

  • Sweet Jade F1, C.maxima. This AAS 2023 winner is a petite, single-serving sized kabocha type. Sweet, earthy and nutritious, the high yielding plants produce 1-2–pound fruits.
  • Sunburst F1, C pepo. A 1985 AAS winner, this pattypan or scalloped type known for its earliness and productivity. It can be harvested at 2-3 inches as a baby squash or grown larger. Its buttery flavor makes this one perfect for stir fry.
  • Bush Delicata, C. pepo. This 2002 winner also is known as sweet potato squash, Bush Delicata is so sweet butter and brown sugar are optional. Its sweet flesh is fine textured without coarse strings. Even the skin is edible.
  • Sugaretti F1, C. pepo. A 2017 AAS winner, this spaghetti winter squash is produced on semi-bush vines that spread only about two feet wide/long. This makes it perfect for small gardens. Its nutty, sweet flesh can be used as a pasta substitute. It stores well and has a long shelf life.
  • Honey Bear F1, C. pepo. An AAS winner in 2009, Honey Bear is a flavorful and sweet, high yielding acorn squash that tolerates cool, moist temperatures and continues to ripen fruits while other varieties succumb to mildew. It displays a compact, bush-type growth habit.
  • Goldilocks F1, C. pepo. A 2021 AAS winner, this golden orange acorn squash produces high yields, is disease tolerance and has a sweet, rich nutty flavor. Vigorous plants produce 10+ fruits each weighing about one pound.
  • Easy Pick Gold II, C. pepo. A parthenocarpic golden zucchini, this variety doesn't need bees for pollination. It has open growth habit and is nearly spineless which makes it easy to harvest with less scaring on the fruit.

Cultivar descriptions courtesy National Garden Bureau.

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