Managing squash vine borers

Admiring my pumpkin growing in the garden, I noticed a problem.

Among the series of vines, some leaves were suddenly wilting while others were fine. A classic sign of squash vine borers. Squash vine borers are one of the most serious pests of zucchini, squash, and pumpkins.

The adult insect is a type of clear-winged moth that resembles a brightly colored orange and metallic green bee or wasp. The adult lays eggs singly at the base of the host plant. The moth’s larva cause damage by burrowing into the vine near the crown of the plant, where it feeds, girdling and killing the leaf. Infestation along the main stem can eventually kill the plant by blocking the flow of water.

Upon further inspection was a small hole about the size of a pencil eraser with fine, sawdust-like frass being pushed out of the hole. This is where the offending larva is found.

Using a utility knife and tweezers, the stem can be sliced lengthwise near entrance hole, and the larva removed and destroyed. The caterpillar resembles a white, segmented grub with a brown head. They may grow up to one inch in length. The vine can be covered with soil to promote rooting and healing.

Insecticide is less effective once the larva is already safely feeding, protected, inside the plant.

Healthy vines can be protected through August with a liquid insecticide containing carbaryl, permethrin, bifenthrin, Spinosad, or esfenvalerate. After final harvest, cultivation will help break the cycle and destroy many pupae trying to overwinter.

As for resistant varieties, butternut squash, green striped cushaw squash, and “cheese” pumpkins (Cucurbita moschata) are resistant to this pest. Good management, variety selection, and continued scouting will enable your family to enjoy fresh your garden further into the season.