Watch: Squash-Vine Borer
You can tell squash-vine borers are present when you see frass (excrement) on the outside of the stem. It looks a bit like sawdust.
Squash vine borers are fat white caterpillars with brown heads. When they tunnel inside stems to feed, it causes healthy-looking plants to suddenly wilt and eventually die.
In late spring or early summer, squash-vine borer moths lay their eggs on squash and pumpkin vines, usually near the base of the plant. Their presence doesn't become apparent until weeks later, when the eggs hatch and the larvae have tunneled into the vines. Squash vine borers may also target cucumber and melon vines. They are found in all areas east of the Rocky Mountains.
Prevention and Control
- If borers are consistently a problem in your area, consider planting butternut squash, which is less susceptible to borer damage.
- Protect young plants from egg-laying adults by covering them with garden fabric. Flowers can be hand-pollinated if necessary.
- Wrap the base of each squash vine (about a 1-foot stretch) with aluminum foil or panty hose to prevent egg laying.
- Check the base of squash vines periodically and destroy borer egg clusters.
- Make a second planting of summer squash in early July after adults have finished laying eggs.
- Slit open infested vines to remove and destroy borers; cover cut vines with moist soil to encourage the formation of new roots. See the technique demonstrated in the video, below.