How to spot it

The adult is a day-flying moth with an orange-red body and dark wings; it looks like a wasp. The damage comes from its caterpillar, white with a brown head and up to 1 inch long, inside the stem. Look for holes near the base of the stem with yellow-green crumbly sawdust.

What it does

The caterpillars tunnel through the stem, so a healthy-looking plant suddenly wilts and often dies within days.

What to do now

• Slit the stem lengthwise above the hole, pull out the borer, then bury that part of the stem in moist soil so it roots again.
• Or inject Bt (Bacillus thuringiensis) into the stem where you see the sawdust.
• Pull and throw away plants that die; don't compost them.

Keep it away next time

• Cover plants with row cover from planting until they flower; the moths lay eggs in early summer.
• Wrap the lower stem in a strip of foil or nylon stocking.
• Sow a second crop in midsummer, after the moths are gone.
• Grow butternut or other moschata squash, which resist borers.
• Turn the soil in fall to expose cocoons.

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Plants it affects