Squash bugs are a common pest of cucurbits, preferring squash and pumpkin, then gourds and melons, and sometimes cucumbers. Among the squashes, the winter varieties, such as hubbards and marrows, are most severely effected. Both the adults and nymphs feed on plant leaves and stems by sucking sap from the plant tissues. While feeding, they inject a toxic substance into the plant, which causes yellowing of the leaf foliage and eventually wilting and death of the plant. This condition is called Anasa wilt of cucurbits.
Squash bugs are also the vector for a recently recognized wilt of cucurbits called Yellow Vine Decline. Plants are infected with the bacteria through feeding of squash bugs. Symptoms usually begin with the plant turning yellow. When cut, affected stems show a brown ring of discoloration in the phloem cells. Eventually affected plants wilt and die.
Adult squash bugs are 5/8 inches long and approximately 1/3 inch wide. The adults are winged, brownish black insects, sometimes mottled with gray or light brown on the back, and have a flat back. The insects have an unpleasant odor when crushed. They overwinter as adults in leaf litter and debris, emerging in spring as the cucurbit vines begin to grow. Clusters of brick-red eggs are laid in the angles between leaf veins on the underside of the leaves. Hatching occurs in 7-14 days. Young nymphs have a green abdomen, and crimson head, thorax and legs. Older nymphs are light gray with black legs. One generation of insect occurs each year, but the extended egg-laying period of the females results in all life stages occur throughout the summer months.
Squash bug adults and nymphs hide on the undersides of leaves, near the crown of the plant, under clods of dirt or any other protective cover. They are gregarious, feeding in groups, and quickly move away when disturbed.
Early detection of squash bugs is vital to effective control. Adults are very difficult to kill and can cause considerable damage. Plant varieties of squash and pumpkin that are resistant, including Butternut, Royal Acorn and Sweet Cheese. Handpick adults and egg masses to reduce insect numbers in the garden. Spray or dust the plants with an insecticide, such as Sevin (carbaryl) as soon as the vines begin to run. Reapply the insecticide as directed on the label. Remove and bury or burn all garden debris in the fall to eliminate overwintering sites.
Always read and follow all directions and precautions on the insecticide label.
Sarah Browning is a Horticulture Extension Educator with the University of Nebraska Cooperative Extension in Dodge and Saunders Counties. She can be contacted by phone at 727-2775: by mail at 1206 W. 23rd Street, Fremont, NE 68025: or by e-mail at sbrowning2@unl.edu
