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Squash Bugs

Garden pest · Anasa tristis

Description​

Squash bugs are sap-feeding insects that attack squash, pumpkins, and other cucurbits. Adults and nymphs pierce plant tissue and suck out sap, especially from leaves and stems. Their feeding can leave pale speckles that turn yellow or brown; heavily infested leaves may wilt and die. Young plants can be stunted or killed, while established plants may lose enough foliage to reduce fruit production. Squash bugs can also feed on fruit. In parts of North America, they can spread cucurbit yellow vine disease, which causes rapid yellowing and wilting. The insects shelter around the base of plants and beneath leaves, making an infestation easy to miss until damage is substantial. Populations often build through the growing season, so a few bugs on a vigorous plant are less concerning than numerous bugs or egg clusters on young plants. Squash bugs are most often a problem on summer and winter squash and pumpkins.

Symptoms​

  • Yellowing leaves
  • Pale speckles or stippling
  • Wilting
  • Stunted growth
  • Leaves dropping
  • Insects visible on the plant

How to Identify​

Look beneath leaves, particularly near the veins, for tight clusters of shiny bronze or copper-colored eggs. Newly hatched nymphs are small and grayish, with dark legs; adults are flat, elongated, gray-brown insects about 5/8 inch (1.5 cm) long, often with alternating light and dark marks along the abdomen’s edge. They may hide at the plant base and give off an unpleasant odor when disturbed. Stink bugs are generally more shield-shaped. Squash vine borers can also cause wilting, but typically leave a hole and sawdust-like frass near the stem base. Finding squash bugs or their eggs alongside feeding damage supports the diagnosis.

Prevention​

Inspect the undersides of leaves at least weekly, starting when plants are young, and remove egg clusters before they hatch. Clear weeds and old crop debris that provide hiding places; remove and dispose of spent cucurbit vines promptly after harvest. Keep plants adequately watered so they can better withstand feeding, without assuming that water will cure bug-related wilt. Floating row covers can keep bugs off young plants, but remove the covers when flowers need insect pollination unless you pollinate by hand. Where squash bugs recur, consider less-preferred crops such as butternut squash, though no variety is completely protected. Check nearby cucurbit plantings too: adult squash bugs can fly in, so moving the crop to a new bed alone will not reliably prevent them.

Treatment​

Start by hand-picking adults and nymphs into a container of soapy water. Crush or scrape egg clusters from leaf undersides, checking repeatedly because new eggs may appear. Lay boards near infested plants overnight; bugs may gather beneath them and can be collected in the morning. If many young nymphs remain, an insecticidal soap or horticultural oil labeled for cucurbits and squash bugs may help when sprayed directly onto them, especially beneath leaves. Follow the label, test a small area first, and avoid spraying during hot weather or when plants are stressed. These products work poorly on eggs and sheltered adults, so repeat inspections matter. For severe infestations, consider a pesticide specifically labeled for squash bugs on your crop, targeting newly hatched nymphs rather than adults. Follow all label directions, keep sprays off open flowers, and avoid times when bees are active. Severely wilted plants may not recover, particularly if they have cucurbit yellow vine disease.

Plants Affected​

Acorn Squash, Butternut Squash, Delicata Squash, Kabocha Squash, Pattypan Squash, Pumpkin, Spaghetti Squash, Zucchini

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