University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Damage

Squash Vine Borer
Melittia cucurbitae

2 (1 = rare 5 = annual)
4 (1 = very little damage 5 = plants killed)

The squash vine borer (Melittia cucurbitae) tunnels in the vines of pumpkins and summer and winter squash; it rarely is found in cucumbers or melons and cannot complete its development except in squash or pumpkins.

Plants Affected

The larva is white, thick-bodied, legless, and 1 inch long when full grown. The adult is a red and black, wasplike moth with clear wings and tends to sit on host plants and beans in the early morning. Reddish brown eggs are laid at the base of the stem just above or below the soil line.

The larva tunnels in the stems of squash, pumpkin, and other vine crops, causing plants to wilt and die in mid- to late season.

Life Cycle

Squash vine borer adults emerge from cocoons in the ground in early summer. Eggs are laid at the base of susceptible plants. About seven days later, emerging larvae bore into the center of the stems to feed. The four to six weeks of feeding will causes the plant to wilt and die. The larvae pupate about 1 to 2 inches below the soil surface. In northern Illinois there is one generation per year, and pupae remain in the soil until the following growing season. In southern Illinois there may be a second generation each season.

Susceptibility varies greatly among varieties. Zucchini, blue hubbard, acorn, and delicata are very susceptible. Butternut squash is highly resistant to attack. When vines begin to run, scout twice weekly for the moths and for the entrance holes and frass. Treat as soon as early damage occurs and again five to seven days later. Then continue scouting and treat as soon as new damage is noted.

Related Resources
Home, Yard & Garden Pest Guide
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic