Identifying the Squash Vine Borer and Squash Vine Borer Damage
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How to Identify Squash Vine Borers
- Eggs: The eggs are tiny, flat, oval, and brown. The eggs are laid around the bases of squash plants.
- Larvae: If you slit open a stem lengthwise with a fine, sharp knife, you will see the borer larva, which has a fat, white, wrinkled body and brown head; it can grow to about an inch long.
- Moth: The adult squash vine borer is a moth about 1/2 inch long. It has a gray or black body, marked with orange-red on its abdomen, legs, and head. The hind wings are transparent, and the front wings are metallic green.
Identifying Squash Vine Borer Damage
- First, the leaves of the plant will likely start to wilt inexplicably.
- Look for holes at the base of the plant and green or orange-yellow sawdust-like “frass,” which is fecal matter (poop!)
- Squash vine borer larvae feed on the material inside the stems of the plants. The stem will start to rot at the site of the feeding first.
How to Prevent Squash Vine Borers
As with most pests, prevention is key.
- Sometimes, the best solution is to start your squash as early as possible. This way, plants will be strong enough to withstand any mid-summer attacks, and you may even be harvesting before squash vine borers become active. If you plant early, you may need to be prepared to cover your plants in case of late frost.
- Do not plant squash in the same area two years in a row. Squash vine borers overwinter in cocoons in the soil. Also, clean up and dispose of ALL plant debris in the fall.
- Dispose of the squash plants as soon as they are finished for the season. In the fall and spring, till the soil to get rid of overwintering pupae.
- Physical barriers can be an effective means of keeping squash vine borers at bay:
- Cover the plants’ stems with a barrier, such as strips of nylon stockings or aluminum foil, to prevent egg laying.
- Before flowers appear on the plants, use row covers to keep squash vine borers away. The covers will need to be removed for pollinators, eventually. This will not only give you a head start over pests, but protect your plants from strong heat and frost.
- Adding beneficial insects such as parasitic wasps to your garden prior to the vine borer’s egg stage can be helpful, as these wasps are the borers’ natural enemies.
- If you give up on zucchini, which is susceptible to vine borers, try growing a squash that’s more resistant. Butternut squash and Cucuzzi (Lagenaria siceraria)—also known as the snake gourd—tend to be resistant to squash vine borer attacks.
- Plant extra squash for the pests! This pest is around for only 6 to 8 weeks and can only eat so much (or so we think!), so making sure you have plenty of plants to spare can help you avoid a total loss for the season.
How to Get Rid of Squash Vine Borers
If you’re already seeing signs of squash vine borers, use these methods to get rid of them or at least minimize their damage to your crops.
- If you catch them VERY early, you can manually remove the squash vine borer. Locate the entry point of the larvae, then slit the stem lengthwise with a fine, sharp knife to remove the larva by hand. One plant can house several larvae. Carefully remove the larvae without doing more damage to the plant. After removal, cover the slit stem section with moist soil above the point of injury to promote the formation of secondary roots. Also, extra rich soil near the vines helps to reroot.
- If you can find the entrance holes and “sawdust,” try inserting a wire and threading it through the stem for some distance to kill the larvae inside.
- Sprinkle diatomaceous earth around the stalks when the squash vines are small, or the threat of squash vine borers is high (early to mid-summer). Reapply after rain. Also, build up the soil around the vines. Or, sprinkle black pepper around the plants as a defense.
- If possible, catch and destroy the moths at twilight or in the early morning when they are resting on the upper leaves of the plants.
- There are insecticides that work, too, but timing is critical; they are only truly effective when applied at the time when eggs are hatching.
- The bacteria Bacillus thuringiensis v. kurstaki (“Bt”) is a natural insecticide that can be injected into and applied to the squash stems.
- Insecticides containing the ingredients carbaryl (Sevin) or permethrin will work on squash vine borers, too. Always be sure to read labels and warnings carefully before application of any insecticide.
- Consult your local cooperative extension service for advice on appropriate chemical controls.
- Trap the adult orange moths with yellow sticky traps and yellow-colored bowls of soapy water.
- A trap crop of very early-planted Hubbard squash can be used to alleviate pest pressure on other squash.
- An old folk remedy from The 1963 Old Farmer’s Almanac says that wood ashes were effective against the squash vine borer.
Learn about another main squash and zucchini predator: the squash bug.
Do you have any tips for controlling these pests? Let us know in the comments below!
Catherine Boeckmann
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I suggest to plant 1 or 2 radish plants about 2 inches by the base of the squash. Radish plant naturally repels the moths along with other common pests such as aphids and others. Just don't harvest these radish and collect the radish seeds for next season.
Last year I tried an experiment with DE and its effects on the larvae. It had zero effect, unfortunately. Those things are too tough skinned for DE to work. But, if spinosad is sprayed into the holes where they are, it kills them within seconds. Also, the moths here in Nw Florida are bright orange like the color of a safety vest. Thanks for this article.
Most times I let the beneficial insects get the worms, wasps of all types in my garden are welcome. Every day they patrol my tomato plants and grab the tender little caterpillars feasting on my tomato leaves. But, I don’t have space for a lot of squash plants bush or vines, so I have to be a bit more aggressive with the SVB’s.
Hopefully this information will encourage others to let wasps live around their garden as long as they’re not hurting anyone. They’re absolutely one of the best beneficial bugs in the garden.
We gave up growing zucchini because of this pest. Then it was suggested to plant your seeds later. We have not had a problem for 2 years in a row since we have done this. For us in Baltimore City we plant on June 21. Plants grow really fast when planted this late and the ten foot bed full of zucchini have been borer free.
Can you use fine mosquito nets over the wooden planters?
Hi, thanks for reading this! Help, please! Imagine my surprise seeing this critter, squash-borer, when searching for the whitish, small grub-like/maggot-like bug that has about destroyed the bulb/roots of all types/sizes of our iris. First time I have ever seen this happen. Could it be the same critter? I do not use pesticides, FYI, we build and make use of ingredients in the mix we create using equal parts of organic topsoil, mushroom compost, composted black Kow/or other cow manure, and peat moss. It’s always a success, and is as organic as I can establish. Part of the reason is because for 3 years now, I have devoted our former-horse farm’s pastures to an organic pollinators’ paradise, after observing how well the Monarch Butterflies’ native Common Milkweed was growing wild here each year; we now allow it grow as need-be before mowing it down after the MB migration in October. I have been wild-rearing them from eggs, a few dozen at a time, May-October, to contribute to their welfare, since as we know they are almost extinct, and our farm’s location, and all of N. C., is part of the great annual fall migration to Mexico. Thanks again, will keep reading into your files for another answer but they look just like them. Best regards, stay safe, from the Piedmont, of N. C.
Hi Debbie,
It sounds like you are dealing with a similar insect pest, the iris borer. They are a common iris pest and their life cycle is much like the squash vine borer: an adult moth lays eggs on or nearby iris foliage, then these eggs eventually hatch and the larvae tunnel down through the leaves to feed on the iris rhizomes. The eggs are laid in late summer and overwinter until late spring, when they hatch. Therefore, late spring and early summer are the times to look out for these pests and to take action against them.
One thing you can do is to always clean up around your iris bed in the fall. Remove any dying plants, dead leaves, or other debris that borer eggs could overwinter on. This won’t prevent borer issues outright, but will help. In the late spring, look for signs of tiny, 1/4-inch larvae boring through the iris leaves. If you spot them, you can easily squish them with your fingers. Additionally, look into organic products that contain parasitic nematodes (Heterohabditis, Steinernema), which will infect and kill the larvae but won’t be bad for beneficial bugs.
I planted my squash in virgin soil this year. It is only my second year dealing with these pests since This is my second year in NC being from the northwest. I have found that once I’ve removed the infected plants and disposed of, (burned, etc.) that after planting new seeds any seedlings that did emerge were weak and very unhealthy. One had a seed pod attached to its leaves and I carefully squeezed slightly to help it remove the pod and a larvae dropped out from the pod. And yes the plant died before the leaves could open. I have had the cocoons from the moths emerging from the soil early morning. I truly believe that once they kill off the host plant the move into the soil and kill any available seeds or seedlings. I want to know how to kill these pests once they have gotten into the soil. I know the Tomato Horned worm can overwinter in the soil and create problems for the following growing season. So there must be a way to kill these pests without removing and replacing soil. As others have stated I planted in soil that never had anything planted in. But I’m finding these pests are destroying my seeds before they can emerge from the soil. And I’m finding their cocoons coming out of the soil even when all plants have been removed and destroyed.
The clear-wing moth that lays the eggs on the stem has a large range- so it likely came from your neighbours garden.
I have always had problems with borers. I plan to try some other tricks this summer. However, I have recently grown large quantities of butternut squash, and harvested many of them green and early. You can eat them just like zucchini. They are a little tastier and a little less watery.
Do you leave the wire and string in the squash plant to get rid of the larvae or u take it out once you have run it down the stem?
