Squash Bugs in the Garden

Early detection of a squash bug problem is essential for preserving crops. Once an infestation is underway, management is difficult.

Squash Bug

Squash Bug

Squash bugs are among the most common and destructive pests affecting pumpkins and squash.

Photo by: Image courtesy of Bob Hammon

Image courtesy of Bob Hammon

Squash bugs are among the most common and destructive pests affecting pumpkins and squash and are difficult to control. They surface with only one generation each year, but through aggressive feeding and the spread of disease, squash crops are easily decimated. Smaller plants are lost quickly and the runners of established plants wilt before turning black, brittle and unable to bear fruit.

Bob Hammon, a master gardener with the Colorado State University extension program says the effects of a squash bug infestation are swift and devastating. “Squash bugs have a piercing and sucking mouthpart. They suck juices from the plant and transmit a bacterium to the plant. If left untreated, it can feel like you might leave for work in the morning with pumpkins and squash looking fine and when you come home in the evening you can rub the plants between your hands and they turn to dust. When they go down, they go down quick.”

Squash bugs, a large winged insect, roughly 5/8” long with brown coloring, overwinter in leaf piles or debris and emerge in the spring to mate and lay masses of eggs on the underside of squash, cucumber or melon leaves. Eggs will hatch in about 10 days. The feeding process of both nymphs and adults are particularly destructive, piercing leaves and stems repeatedly causing cell structures to collapse. Early detection of a squash bug problem is essential for the preservation of crops. Once an infestation is underway, management is difficult.

“A typical call I get is from someone saying their plants are covered with baby squash bugs asking what they can do. I might have to tell them they’ve lost the battle and they need to start planning next year,” laments Hammon. “Treatments have to start early. Squash bugs tend to congregate around the base of the plant, and any treatment, chemical or organic, has to be applied at the base of the plant before they develop. If you have to spray the underside of leaves to get at the eggs, that is very hard to do with a plant so low to the ground with ten foot vines.”

Manage squash bug problems at the end of the season. Once the last crops have been harvested, clear, bury or burn all leaves and other plant matter from the plot. Without this debris, squash bugs will be unable to overwinter, eradicating the population before it can develop.

Another strategy for avoiding squash bug damage lies in crop selection. A number of squash bug resistant varieties exist, including butternut, early summer crookneck and royal acorn. Rotate crops yearly, replacing prone varieties in a planting area with squash bug resistant varieties or other crops unaffected by this pest.

If a squash bug infestation is already active, insecticides can be employed, but should be applied as early as possible and plants inspected frequently to determine if subsequent treatments are necessary. In a small garden, damage can be minimized through regular inspection of plants and hand removal of eggs, nymphs and adults. Note that the squash bug is closely related to stink bugs and they will emit an unpleasant smell when crushed. 

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