Squash Bugs

Anasa tristis

Insect

Flat, gray-brown shield-shaped bugs that attack squash, pumpkins, and other cucurbits, sucking sap until leaves wilt and collapse. They hide fast and are tough to kill as adults, so the game is finding and crushing the egg clusters early.

🔎 How to spot it

Adults are about 2/3 inch, flat-backed and brownish-gray, almost black up close, with orange-and-brown striped edges along the abdomen. Nymphs hatch with a green abdomen and dark legs and turn gray as they grow, often clustering together. The surest sign is the eggs: neat clusters of shiny, brick-red to bronze oval eggs laid in the vein angles on the undersides of leaves.

🥀 Damage it causes

Adults and nymphs suck sap, causing leaves to speckle, then yellow, brown, and wilt; under heavy feeding the point of attack turns black and brittle and whole vines can collapse, especially on younger plants. They prefer squash and pumpkins but feed on most cucurbits.

🛡️ Prevent it

Cover plants with row cover from planting until bloom, then remove it for pollination, in any bed with a squash bug history. Scout the leaf undersides twice a week and crush every egg cluster you find. Clear out old vines and debris at season end to remove the sheltered spots where adults overwinter, and rotate cucurbits to a new bed.

🧯 If it is already here

Handpick adults and nymphs into soapy water, and scrape off the egg clusters. Lay a board flat on the soil overnight; the bugs gather under it and can be collected and destroyed each morning. Sprays work poorly on the tough adults, so target the young nymphs if you treat, and put your effort into egg-crushing and trapping.

💡 Good to know

Squash bugs are hardest to kill once they are full-grown adults, which is why catching the egg masses and young nymphs is the heart of control. Adults overwinter in debris and emerge to lay eggs as the vines start to run, so a clean fall garden means fewer bugs the next year.

🌱 Plants it attacks

47 plants in the library can be attacked by this pest

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.