Squash Vine Borer

The squash vine borer is here. The infamous larvae of this moth burrow into squash vines eventually compromising the plants ability to transfer water to fruit and foliage. Each year we anticipate the arrival of the adult moth about the second week of June. This year we began scouting June 15th and sighted the first adult on June 18th.

These moths which look more like a wasp are best spotted in the morning on and around winter squash, zucchini, and pumpkins. We have also found they will hang out near the tops of potato plants. These moths will land on the underside of the plant, usually near the base, and lay small reddish/metallic colored eggs. Out of these eggs will emerge larvae that will burrow into the stem of the plant.

We began scouting plants for eggs on June 25th and found only a few. We scouted again on the 29th and found that eggs were on all above mentioned  plants. Our method of control is careful observation and removal of as may eggs as possible. Simply scrape them off with a fingernail.  Next year we do plan on placing a floating row cover over the plants to prevent the Squash Vine Borer from laying eggs.

We will continue to monitor the vines and look for symptoms of larval burrowing. Midday wilting of vines with nighttime recovery is often a good indicator of a borer.  At this point check vines for entry hole and frass. You may be able to use a paper clip to spear the unwanted larvae at or near this entry point. Please refer to the following UW Extension fact sheet for more information.