Squash Bugs by Stephanie Suesan Smith, Ph.D.
Squash bugs are some of the most frustrating pests in the home garden. They feast on a wide array of plants in the curcubit family and can do some pretty serious damage to them. They pierce the plants and suck out the sap, causing the plants to wilt or even die. They are also hard to kill. They can be controlled, though, with a little effort.
To control squash bugs, it helps to understand their life cycle. Adult squash bugs are tiny, 5/8ths of an inch long, and winged with a grayish brown color. The edges of the abdomen and the underside of the insect have orange to orange-brown stripes.
Squash bug eggs are really small but are laid in large groups or clusters that are easy to see. Eggs are reddish in color and are usually laid on the underside of the leaves in the spring. They hatch out into nymphs in about one to two weeks. Nymphs are wingless, spiderlike, and often covered by a white powder. They range in color from mottled white to greenish gray and have black legs. Later, they begin to turn dark brown and resemble adults. After molting several times into increasingly larger nymphs, they become adults. The whole process from egg to adult takes four to six weeks.
An important cultural control is sanitation in the garden. Remove old curcubit plants as soon as they stop producing and compost them. Remove garden debris that may allow squash bugs to hide under it, such as boards. At the end of the gardening season, remove all mulch and compost it or till it under in place to remove overwintering sites for the adult squash bugs. During the gardening season, regularly check under the leaves of curcubits and remove egg masses as soon as they are deposited.
If cultural controls do not suffice to keep squash bugs in check, then you will have to move to chemical controls. The first line of chemical control is horticultural oils such as neem oil. You must thoroughly spray the plant, reaching the undersides of each leaf and the crowns of each stem. The horticultural oils are most effective on nymphs. You can use more toxic chemicals such as permethrin or carbaryl, but these kill beneficial insects and bees and are not really more effective than using the horticultural oils and hand picking the adults off the plants. When you pick the adults off the plants, drop them in a jar of soapy water to kill them.