What can I spray to deter squash vine borers on my plants?

Asked June 15, 2020, 11:47 AM EDT

What can I spray to deter squash vine borers on my plants?

Harrison County West Virginia

1 Response

As far as I know, there's nothing that can be applied to plants to deter their attacks. Mitigating squash vine borer damage revolves around reducing the number of moths in the area, using planting dates to avoid damage, and dealing with larvae after they appear. Below is an email I wrote another client about controlling squash vine borers you may find helpful.

Squash vine borers are day-flying moths that borer into various squash, especially zucchini and pumpkin, as larvae. Most integrated pest management solutions for squash vine borers involve preventative measures and detection as once borers are inside the squash stem they are difficult, if not impossible, to control.

Squash vine borers overwinter as pupae in the soil, so tilling the garden in the fall after crops are harvested is an effective way to reduce the number of moths the following season. It won't eliminate the pressure from squash vine borers entirely as adults from other areas can fly in, but fewer moths should mean fewer vines infested.

You can monitor for adult moths by placing yellow bowls (e.g. plastic party bowls) filled with soapy water around the plants beginning in mid-June. When moth activity is noticed, you can use a two pesticide sprays spaced seven days apart to kill the eggs and newly hatched caterpillars.

Once caterpillars are in the stems and you notice the frass, you can remove the caterpillars by splitting the stem with a sterilized knife and pulling the caterpillars out. Squash vines will often send down additional roots when in contact with soil, so once the caterpillars are removed, you can move soil over and past the infested stem to encourage the vines to root beyond the damage.

For more information, please refer to the following resources:
PSU fact sheet
UK fact sheet