Squash Bug

• Gray-brown shield-shaped bugs, about 5/8 inch, clustered on squash plants
• Bronze or tan patches on leaves that yellow and die — called anasa wilt
• Shiny, copper-colored egg clusters on the underside of leaves between veins
• Wilting that starts in one part of the vine and spreads
• Black, tarry spots on leaves and stems from feeding damage

Adults overwinter under garden debris and leaf litter, emerging in late spring. They lay egg clusters in late May through July, typically on the underside of squash leaves. Nymphs hatch in one to two weeks and go through five instars before reaching adulthood. There is generally one generation per year. Adults hide under boards, mulch, and plant canopy — making them hard to find during the day.

1. 01Check leaf undersides weekly starting in late May for bronze egg clusters — crush them immediately
2. 02Hand-pick nymphs and adults in the early morning when they cluster and move slowly
3. 03Place boards near plants as traps — bugs hide under them overnight. Check and destroy each morning
4. 04Maintain good garden sanitation: remove spent vines promptly after harvest to eliminate overwintering sites
5. 05Neem oil or insecticidal soap can suppress nymphs but are less effective on adults
6. 06Avoid thick mulch directly around squash stems — it provides hiding cover

If you're losing plants to anasa wilt every year despite diligent egg removal, an extension office can advise on whether trap crops (like blue hubbard squash planted as a border) might be effective for your scale.

• Squash Bug— University of Maryland Extension
• Squash Bug Management— Colorado State University Extension