Squash Vine Borer: A Squash Nemesis
Adult Squash Vine Borer. We all hate them.
If you’ve grown a garden in Houston and were hoping to get beautiful summer squashes, you likely know the frustration and sadness of dealing with the dreaded Squash Vine Borer.
This is a little moth that is active in April/May in the South, when they lay tiny brown eggs at the base of squash plants. After hatching, the larvae bore into the stems of the plants, feeding inside the vines. This causes the plant to wilt suddenly, even though it may look healthy otherwise. But if left unchecked, it can kill the plant within days.
How to Prevent Squash Vine Borers
A good way to postpone Borer damage is to plant your squash seeds early. We’re talking Late February/Early March to avoid peak moth activity in late May–June.
Use Row Covers: You can cover young plants with floating row covers to prevent adult moths from laying eggs, but be sure to remove the covers when flowers appear so pollinators can get in. Otherwise you ‘ll have beautiful plants…but no fruits.
Monitor for Eggs: Check the base of stems and under the leaves daily. These moth eggs are tiny, flat, and brown—remove by hand and destroy.
Wrap Stems: You can try wrapping the lower stems with aluminum foil or nylon stockings to deter egg-laying. This works, but you have to stay on top of it and continue to wrap the plant as it grows.
Choose Resistant Varieties: Choosing resistant varieties might be your best option. The soft, summer varieties we’re used to, like yellow squash and zucchini, are Cucurbita pepo. These are the ones that Squash Vine Borer loves.
Some varieties of squash (like butternut and other Cucurbita moschata types) are less susceptible because of their tougher, thinner vines. The larvae have a hard time eating through them.
Companion Planting: I love the idea of companion planting as much as the next guy, but it rarely works to deter pests. My squash were virtually surrounded by nasturtiums, which supposedly deters the moth, but they still got it. This is not to say do not plant nasturtiums or dill, because it doesn’t hurt and pollinators love them, but you’ll still need to be vigilant and proactive against the Borer.
How to get rid of them
Borer damage to squash vine. Photo courtesy of Bonnie Plants.
Once you see the yellow, sawdust-like frass (bug poop) coming out of the stem or on the soil near the stem, there are a few things you can do. If you see wilting, cut a slit in the stem with a clean knife where you see frass. Remove the white grub, then bury the stem section with soil—it may re-root and recover.
You can also Inject BT directly into stems before eggs hatch. This organic treatment targets larvae. Neem oil may deter egg-laying, but is less effective once the borer is inside.
Once the larvae are inside and eating the plant, there’s really little you can do. Moths lay several eggs at a time which means several larvae could be working inside the plant, and they work fast. Try these methods, but usually, the plant will need to be pulled up and thrown away. I don’t like it, either, but that’s life in the garden.
We, as Garden Girls, have tried many things to keep this bug away, but it seems inevitable that Squash Vine Borer will get your squash plants. Remember to plant seeds very early in the Spring, wrap the base of the stem, and spray it often with Neem and BT. These activities should help deter the pest long enough to get you at least a few good squashes and zucchini. Good luck and happy gardening!
