Squash bugs gather, mate, and lay eggs as soon as the weather warms in late spring. Because you grow squash bugs' favorite foods-summer squash and pumpkins-you'll need to plant defensively. The best thing you can do is to protect your plants with a row cover. Install the cover at planting time, and leave it on until the plants begin to bloom. Once flowers appear, remove the cover so bees and other pollinators can get to the flowers. Squash bugs will move in, but by then your plants will be robust enough that they should produce well despite the insects. Meanwhile, reduce squash bug numbers by handpicking them off your plants and dropping them into a container of soapy water for easy disposal.
Examine plants for squash bug eggs (brick red clusters on leaves), and destroy them before they hatch into nymphs. Squash bugs will feed on the fruits of your plants, so as your plants decline, gather ripe pumpkins and store them indoors. Pull up failing plants a few at a time so any remaining squash bugs are forced to congregate on the plants left behind. As the last plants are pulled, shake them over a wheelbarrow filled with hot, soapy water. This reduces the number of adults that would otherwise spend the winter in your garden, ready to attack again next spring.