Squash Bug—Anasa tristis
Squash bugs feed on cucurbits (vine crops) and prefer squash and pumpkin. They spend most of their time around the base and stems of the plants and on the undersides of leaves. When crushed, they give off an unpleasant odor.
Both nymphs and adults suck sap from the leaves and stems, apparently at the same time injecting a toxic substance into the plant causing wilting. After wilting, vines and leaves turn black and crisp, and become brittle. Under heavy feeding pressure, small plants can be killed; larger plants can have many affected leaves and vines.
More importantly, squash bugs are the vector of a newly recognized disease of cucurbit crops, Yellow Vine Decline. Melons, watermelon, and pumpkins are susceptible to this disease. The bacteria that causes this disease is injected into the plant while squash bugs feed. The disease results in yellowing, wilting and death of the plant.
Adult squash bugs are flattened in appearance and approximately ½ to ¾ inch long. Gray to black in color, adults are winged with orange and brown stripes visible on the edges of the abdomen.
The five nymphal instars range in length from 1/16 to 1/2 inch. The first instar is green with rose-colored legs, antennae, and head. These appendages darken in a few hours. Subsequent instars are grayish-white with dark heads, legs, and antennae. The last two instars have noticeable wing pads.
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Identification and Control Information
- Sucking Insects That Affect Vegetable Plants—University of Maine Cooperative Extension
- Squash Bugs in Home Gardens (PDF)—University of Minnesota Extension
- Squash Bug and Squash Vine Borer: Organic Controls (PDF)—ATTRA, United States Department of Agriculture
- Integrated Pest Management for Home Gardeners and Landscape Professionals: Squash Bug (PDF)—University of California
[Photos, left to right: Whitney Cranshaw, Colorado State University, Bugwood.org; Alton N. Sparks, Jr., University of Georgia, Bugwood.org; Whitney Cranshaw, Colorado State University, Bugwood.org]