Squash vine borer moths look and act like paper wasps and have a 1 to 1½ inch wingspan, with metallic green forewings. Females lay red eggs near the base of plant stems. The mature larva or caterpillar is a thick, white wrinkled worm with a brown head, and is about 1 inch in length. The eggs are dull red, 1/25th inch in diameter, and are found glued to the leafstalks and stems of squash vines. The eggs produce smooth, white caterpillars that bore into the center of the vine a few days after hatching. The pupa is dark brown, 5/8 inch long, and found in an earthen cell in the soil.
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| Squash Vine Borer Larvae (R. Bessin) |
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| Squash Bug Nymphs (R. Bessin) |
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| Adult Squash Vine Borer |
Most management options are limited to control the hatching larvae before they enter the plant.
A home gardener may have some success with deworming the vines. At the first signs of the sawdust like frass (fecal material from feeding larva), vines can be slit lengthwise near where the damage is found and the borers removed. The stems should be immediately covered with earth.
Sanitation is also important. After harvest is complete, vines should be removed from the garden and composted to prevent the remaining borers from completing larval 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.
To reduce the number of borers for the next year, destroy crop residue after harvest, and rotate planting sites.
If insecticides are needed, spray or dust the plant stems at their base. Start treatments when vines begin to run or when the first adult borers are detected. Repeat in 7-10 days. Two applications help manage most squash vine borer adults.
Additional Information
Squash Vine Borer - Penn State University
Squash Vine Borer - University of Kentucky
Clearwing Moths - University of California IPM
Squash Vine Borer - Insect Diagnostic Laboratory - Cornell University
