The squash vine borer is a key pest of summer and winter squash, gourds and pumpkins. It is also seen in cucumber, gourd, and melon in Ohio. Unfortunately, it is usually noticed only after it has done its damage. Symptoms appear in mid-summer when a long runner or an entire plant wilts suddenly. Infested vines usually die beyond the point of attack.
Squash Vine Borer Frass
Sawdust like frass near the base of the plant is the best evidence of squash vine borer activity. Careful examination will uncover yellow brown excrement pushed out through holes in the side of the stem at the point of wilting. If the stem is split open, one to several borers are usually present. The caterpillars reach a length of 1 inch and have a brown head and a cream-colored body.
The adult squash vine borer is a stout dark gray moth with ‘hairy’ red hind legs, opaque front wings, and clear hind wings with dark veins. Unlike most moths, they fly about the plants during the daytime, appearing more like a paper wasp than a moth.
This insect overwinters as a full-grown larva or a pupa one to two inches below the soil surface. Adult moths begin to emerge about the time the plants begin to run, and moth flight continues through mid-August.
The small brown eggs, laid individually on leaf stalks and vines, hatch in seven to 10 days. The newly hatched larva immediately bores into the stem. A larva feeds for 14 to 30 days before exiting the stem to pupate in the soil. There are 1 to 2 generations per year.
Management – The key to squash vine borer management is controlling the borers before they enter the stem. Once inside the vine, insecticidal control is ineffective. Poor timing of sprays is the usual cause of inadequate control. Very early signs of larval feeding indicate that other eggs will be hatching soon. Use two insecticide applications 7 days apart to control newly hatching larvae and continue to monitor for additional activity. Sprays need to penetrate the canopy to cover the vines to be effective.
Home gardeners may have some success with deworming the vines. At the first signs of the sawdust like frass on vines, slice lengthwise near where the damage is found and remove the borers. Cover stems immediately with earth. Sanitation is also important. Vines should be removed from the garden and composted after harvest is complete to prevent the remaining borers from completing development. Burying a few nodes along each vine will encourage rooting at these nodes. This will lessen the impact if squash vine borers girdle the base of the vine.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!