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Squash Bug

by William F. Lyon, Julie A. Neal    

The squash bug is one of the most common and troublesome pests attacking squash and pumpkin plants. Both nymphs and adults suck sap from the leaves and stems, apparently at the same time injecting a toxic substance into the plant causing a wilting known as Anasa wilt of cucurbits. This closely resembles bacterial wilt, a true disease. After wilting, vines and leaves turn black and crisp, and become brittle. Small plants are killed entirely, while larger plants have several runners affected. Squash bugs are often found in large populations, congregated in dense clusters on vines and unripe fruits. Sometimes no fruits are formed.

Identification

Adult squash bugs are rather large, about 5/8 inch long and approximately 1/3 as wide. Adults are winged, brownish black, sometimes mottled with gray or light brown, flat-backed, and give off a disagreeable odor when crushed. Young, called nymphs, are whitish to greenish-gray, with black legs. Bugs vary in size from tiny, spider-like individuals when first hatched, to maturing nymphs, which are nearly as large as adults. Young nymphs have red legs and antennae with a green abdomen. A few hours later, red parts become black. Late instars are of a dark, greenish-gray color. Eggs are yellowishbrown to brick red laid in groups or clusters.

Life Cycle and Habits

Unmated adult squash bugs overwinter in the shelter of dead leaves, vines, boards or buildings and fly to cucurbits when vines start to grow. Following feeding and mating, egg laying soon begins. Masses of eggs, each containing about a dozen or more, are usually deposited on the undersides of leaves in angles formed by the veins. Egg laying by the overwintering females continues until midsummer. Eggs hatch in about 10 days or more, and the nymphs pass through 5 instars requiring 4-6 weeks to reach adulthood. Only one generation develops each year and new adults do not mate until the following spring. Squash bugs are secretive in habit. Both adults and nymphs are found clustered near the plant crown, beneath damaged leaves, under clods or in any protective groundcover. They all scamper quickly for cover when disturbed. Because of the protracted egglaying period, all life stages occur throughout the summer months.

Control Measures

Early detection of adult squash bugs is very important since they are difficult to kill and can cause considerable damage.

Prevention

If only a few vines are involved, it is best to collect and destroy the bugs and crush their egg masses. Some people place pieces of board or shingles on the ground near the plants to concentrate the number of individuals in an accessible area. Plant remnants may be buried or burned at the end of the year. It is a good idea to select varieties of squash and pumpkin resistant to the squash bug. Since there is only one generation per year, damage can be greatly reduced by keeping vines covered until blossoming begins. Remove the cover for pollination purposes.

Insecticides

Apply carbaryl (Sevin) according to label directions and safety precautions when bugs first appear. Rotenone is effective on younger bugs, but not the adults. Repeat applications as needed for best control.

NOTE: Disclaimer - This publication may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registrations, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author and Ohio State University Extension assume no liability resulting from the use of these recommendations.


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