Squash bugs (Anasa tristis) are a frequent pest of squash and pumpkins, particularly winter squash. They do not bother summer squash as much. Young plants and flowering plants are most at risk.
Description
Adult squash bugs are about 5/8 inch long and gray to brown. The abdomens have alternating orange and brown stripes. The eggs are oval, about 1/16th inch long, and orange to bronze. The nymphs are from 1/10-1/2 inches long. They start out with a green abdomen and black head. As they go through the instars, or molts, they turn first light grey, then brownish gray with black legs.
Life Cycle of Squash Bugs
Adults overwinter under plant debris, beside buildings, or in other places that are out of the cold and rain. They emerge as temperatures warm up enough for squash to grow.
The female last about 20 eggs on the underside of the squash leaf. The eggs are visible to the naked eye. They hatch in about ten days. The nymphs mature in four to six weeks. Depending on how long the warm season is, there may be multiple generations each year.
Damage Caused by Squash Bugs
Squash bugs pierce the leaves of the squash and suck the sap out of them, leaving behind yellow spots that then turn brown. Since this removal of sap also affects the movement of nutrients and water, severe infestations may kill a young plant. Older plants have more foliage, so they are not as badly affected. Squash bugs will eat squash and cucumbers as well as the plants.
Management of Squash Bugs
Adult squash bugs are tough to kill. You will have the best luck targeting the eggs and nymphs.
Cultural Management
Inspect your squash plants every other day. Look on the underside of the leaves as well as the tops. Dropping squash bugs into a jar of soapy water will kill them. Crush the eggs you find.
Trap squash bugs by laying a board or newspaper on the ground near the squash plants. The squash bugs will go under it at night. Go out early in the morning and crush or drown the squash bugs you find.
Keep your garden clean of plant debris, especially squash, pumpkins, and cucumbers. Remove as much plant matter as possible in the fall so the squash bugs do not have anywhere to hide over the winter.
Chemical Management
Applying a mix of diatomaceous earth and pyrethrins around the base of the plant when you first detect the eggs will control the squash bug nymphs. Reapply the treatment a week later. If you see more eggs, repeat the two treatment applications. Both diatomaceous earth and pyrethrins are allowed in organic gardens. Use horticultural diatomaceous earth, not the diatomaceous earth for pools.
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