Click for larger image Squash bug (Hemiptera) on yellow squash (Cucurbita)

Squash bugs, Anasa tristis, are sometimes mistakenly called stink bugs because they may give off a foul odor when squashed. Stink bugs have wider shieldshaped bodies than squash bugs. Squash bugs are pests on all cucurbits including cucumbers, muskmelons, pumpkins, squash, and watermelon. Squash and pumpkins are the most susceptible to squash bug attack.

Symptoms and Diagnosis

Squash bugs destroy plant tissue by sucking out the sap from leaves and stems and depleting nutrients from the plant. This feeding causes leaves to wilt and dry out. They eventually turn black and fall off the vine. Adult pests can be seen feeding on main stems. Nymphs are more likely to be found feeding on the undersides of leaves.

Life Cycle

Adult squash bugs are brown or black, flat-backed, and 1/2 to 3/4 inch long. In the spring when plants begin to develop runners, elliptical, yellow or brown eggs are laid in groups on the undersides of the leaves. Immature stages (nymphs) have gray-green bodies and red or black legs. Adults overwinter in garden debris and emerge the following spring. There is only one generation per year.

Integrated Pest Management Strategies

1. The key to management is early detection and control. There are two critical times when plants are most vulnerable to damage. First is when plants are seedlings with undeveloped root systems and vulnerable to damage from overwintering adults. The second critical time is as plants begin to flower and eggs first begin to hatch.

Handpick bugs and eggs and destroy them by dropping them in a bucket of soapy water. Egg masses are either orange-yellow or bronze in color and can usually be found on the undersides of leaves.

2. Cover young plants with row covers of nylon netting or cheesecloth to deter bugs from feeding on them.

3. Plant resistant squash varieties like ‘Butternut’, ‘Royal Acorn’, ‘Sweet Cheese’, and ‘Black Zucchini’.

4. Do a thorough garden cleanup in the fall in order to remove overwintering sites. Tilling plants into the ground after the growing season helps to expose the overwintering stage of the squash bug and reduce their populations.

5. Use an insecticidal soap every 3 days for the first 2 weeks after squash bugs first emerge in the spring. Insecticidal soaps are contact insecticides, so take care to make sure that all plant surfaces are covered, especially the undersides.

6. Dust plants with permethrin or sabadilla.

Organic Strategies

Strategies 1, 2, 3, and 4 are strictly organic approaches. For an organic approach to Strategy 5, consult the Organic Materials Review Institute (OMRI™) for appropriate insecticidal soap products.

More images:

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Adult squash bug and dead nymphs (Hemiptera) on squash (Cucurbita)
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Adult squash bug (Hemiptera) on squash (Cucurbita)
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Adult squash bug (Hemiptera), nymphs, and eggs on squash (Cucurbita)
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Squash bug adult (Hemiptera) on squash (Cucurbita)
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Adult leaf-footed bug (Hemiptera); Note, flattened tibias on hind legs
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Squash bug (Hemiptera ) eggs on squash (Cucurbita) leaf
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Close-up of squash bug (Hemiptera ) eggs on squash (Cucurbita) leaf
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Squash bugs (Hemiptera ) are in the leaf-footed bug familly but they do not have the characteristic "leaf foot" like these leaf-footed bug nymphs on a pumpkin (Cucurbita)