How do I prevent damage to my squash plants from the squash vine borer?
The squash vine borer is a common pest of squash and pumpkins in home gardens in Iowa. Damage first appears as wilting of the vines. Eventually affected plants may collapse and die.
The adult squash vine borer is a wasp-like moth. Adult borers emerge from the ground in late spring. Adult females lay eggs at the base of squash and pumpkin vines. Within a few days the eggs hatch and the larvae bore into the stems to feed. Larvae feeding in the center of the stems block the flow of water to the rest of the vine, causing it to wilt. Severely affected plants wilt and die. The larvae feed inside the vines for several weeks, then exit the stems and borrow into the soil to pupate. They remain in the soil until late spring of the following year.
Preventing squash vine borer damage usually requires treating the base of squash and pumpkin vines with a residual insecticide when the moths are flying (early to mid-June in Iowa). Home gardeners can apply carbaryl (Sevin), permethrin (Eight), bifenthrin, spinosad, or other labeled garden insecticides. Sprays are generally more effective than dusts.