Squash Vine Borer on Zucchini

Squash Vine Borer (Melittia cucurbitae) is a clear-winged moth in the Sesiidae family whose larvae tunnel into stems of cucurbits like zucchini, squash, pumpkin, and sometimes cucumber. Damage is seasonal in most of North America (zones 3-11) and centers on the stem base, where females lay eggs at or just above the soil line.

The adult moth looks like a small hornet with clear wings and is active during warm daylight hours; eggs hatch into larvae that bore immediately into the plant. Once inside the stem, larvae chew a tunnel and feed until they pupate - this internal feeding often causes rapid wilting and can kill individual vines within days.

Because the insect attacks inside the plant, visible damage is deceptive: leaves can look fine until larval feeding severs the water column. Early diagnosis and quick action save vines; late detection often means the vine must be removed to protect the bed and future plantings.