The squash bug, Anasa nistis, is a common pest for plants in the cucurbit
family such as watermelon, cucumbers, pumpkins and, of course, squash.
Both the adults and young bugs (nymphs) feed on the leaves and stems of
plants. As they draw the sap out, a toxin is left behind that causes the
plant to turn black and wilt. Referred to as anasa wilt, this condition
will kill young plants and cause stems to die back, and results in
malformed fruit or even no fruit on established plants.
Adult squash bugs are about ¾ of an inch long, with a flat,
brownish-black back, and wings. Sometimes there will be a tan or gray
mottling on the back as well. The nymphs begin life with red legs and a
green abdomen, turning darker as they mature.
Adult bugs hibernate during winter and emerge in spring to mate and lay
eggs. The eggs are produced until mid-summer. You will find them on the
underside of leaves clustered around the leaf veins. The adults and
nymphs are likely to be found beneath the cover of dead leaves, near the
crown of the plant or under mulch. Look under anything that offers them
Since squash bugs only produce one generation during the growing season,
early detection will give you the upper hand in dealing with this pest.
If you can break the life cycle this year, there will be less of a problem
Here are a few ways you can combat squash bugs.
- First, cover your plants with a floating row cover. Leave this on until blooms start appearing. At this point the protection should be removed so that pollinating insects can reach the flowers.
- Instead of straw use a dense mulch material around the plants such as grass clippings, compost or sawdust. This will eliminate at least one place where squash bugs like to hide.
- Hand-pick and destroy both the insects and the eggs. If you place a board on the ground near plants they will congregate under it. This makes it easier to get rid of a large number all at once.
- If your plants are infested, insecticides can be effective on the young bugs. Use something earth-friendly and safe for food crops such as an insecticidal soap. You may need to spray several times.
- To prevent squash bugs from overwintering and becoming a problem again next year, clean up your vegetable garden in fall, pull out and throw away the dead plants, and remove anything that they can hibernate under such as straw, plant debris or wood piles.