By now your winter squash and pumpkins are probably in full growth, producing flowers and fruit. However, other creatures are also impressed with your squash’s growth. Squash bugs are one of the toughest home garden pests to control safely. These brown- or gray-colored insects seem to move in hoards and can quickly decimate a patch of cucurbits.
First, it’s important to know thy enemy. Squash bugs overwinter in your garden in plant debris, on logs, and under rocks. Once the warm spring weather hits, the adults emerge to feed and mate. The females then lay copper-colored eggs on the undersides of leaves. Often these eggs are laid in clusters in between leaf veins. In a week or so, the young green nymphs hatch and start feeding on the leaves. They look like miniature versions of the adults, only in a different color. The nymphs and adults suck plant juices from the leaves and stems, causing the plant to collapse. When these insects gather in large numbers, they also attack the fruits, especially pumpkins, causing rotten areas where they have fed. A second generation of nymphs and adults can occur in warm-summer areas. This allows more nymphs to evolve into adults to overwinter, creating more squash bugs the next year.
To control squash bugs, remove mulch from around the plant, where they can hide. You can also use their propensity to hide in dark places to catch them. Place boards around the base of squash plants, and “harvest” and kill the squash bugs you find under the boards in the morning. Check regularly for the copper-colored eggs on the leaf undersides, and squish them without harming the leaf. In small plantings, handpick the adults and nymphs, and drop them into a pale of soapy water. Using spinosad and pyrethrum sprays when the nymphs are young helps reduce the population. Sprinkling diatomaceous earth around the base of plants also wards the insects off.