Special Edition - Squash Vine Borer

For this special edition episode/article of This Week in the Garden, I’ll cover something I’ve seen pop up in the garden this past week: squash vine borer. Squash vine borers will make quick work of your cucurbits, so make sure to get out and start scouting.

Squash vine borers are a moth that use mimicry and look similar to wasps. They’re relatively large in the insect world and have bright red colors. I’ve had the best luck scouting for adults in the evening, after dinner. At this time of day, the adults have slowed down and are often found on the leaves of squash, watermelons, pumpkins, and cucumbers. If you find one, make sure to squash it! Control of squash vine borers is difficult as getting insecticides into the plant stem when the larvae feed is not possible. For this reason, finding and removing adults is the best bet. Adults are most common in June and their numbers will decrease by the beginning of July.

If you notice adult moths, begin checking your plants for damage. Larvae bore into the stems and will slowly kill the plant. If you check your plant daily, you should be able to see where the larvae are feeding. One sign is wilting and yellowing leaves. If you notice this, check the stems for a brown area. That will be where the larvae are feeding and producing waste (frass). If you’re lucky, you might be able to see where the larvae bore into the plant, which will be apparent by frass under the stem, similar to when you see sawdust under a carpenter bee nest. If you find where a larvae has been feeding, remove the stem. Make sure to find the larvae and destroy the stem the larvae is in, don’t leave it in the garden.

Fortunately, squash vine borer only stays in the plants for 4 weeks. If you notice your plants are deteriorating, you have 4 weeks to remove them to break the cycle. Squash vine borers only have one life cycle per growing season, so if you can weather the storm your plants will be safe for the end of the summer. For that reason, if vine borers destroy your cucurbits, you still have time to replant in July.

That’s all for this special edition article from This Week in the Garden. Here’s a helpful link if you have any questions about squash vine borer. If you’ve missed any articles check out our website where we keep them archived and fill out our form if you have any comments or questions. And of course, stay tuned until next time from This Week in the Garden.

-Adam