Squash Vine Borer

How to Prevent and Get Rid of Squash Vine Borers

Squash Vine Borer larvae
Wikimedia Commons

Are your squash plants suddenly struggling? It could be the work of a squash vine borer. Here are tips on how to identify, control, and get rid of the squash vine borer!

What Are Squash Vine Borers?

It can be so disappointing when your squash is thriving and suddenly starts to wilt. This may be the result of a squash vine borer (SVB), which is a type of moth that lays its eggs at the base of squash plants. When the eggs hatch, the larvae burrow (or “bore”) into the lower stems, weakening or killing the plant outright.

Found throughout the eastern United States, squash vine borers typically attack squash, zucchini, pumpkins, and various types of gourds. They prefer Hubbard squash and are not as fond of butternut squash. Other cucurbits, like cucumbers and melons, are not usually targeted.

The borers overwinter in soil as pupae in cocoons. When the adult moths emerge in early to mid-summer, they lay eggs singly or in small groups at the base of plant stems. The eggs will hatch within 1 to 2 weeks of being laid. The larvae will then bore into stems to feed for about 2 to 4 weeks; sometimes they may also bore into the fruit. In northern areas of North America, there is usually only one generation per year; in southern areas, there may be 2 generations.

If caught early, it’s possible to save the plant. If caught after the eggs hatch, it may be too late. Controlling the squash vine borer is mainly about prevention.

Identification

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 ½ 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.

Squash vine borer moth. Photo credit: Judy Gallagher/Wikimedia Commons
Photo credit: Judy Gallagher/Wikimedia Commons

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 the chewed up stem that the larvae produces as it burrows into the plant.
  • 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.

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Squash vine borer larvae can cause major damage to the inside of your squash plant stem. Photo Credit: Donn Cooper, University of Georgia.

Control and Prevention

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.
  • As soon as the squash plants are finished for the season, dispose of them. Till the soil in the fall and spring 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 parasitic wasps to your garden prior to the vine borer’s egg stage can be helpful, as these wasps are the borers’ natural enemy.
  • If you give up on zucchini, which is susceptable 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.

get-rid-of-squash-vine-borer.jpg
Larvae of the squash vine borer can destroy cucurbit stems if not controlled and prevented. Photo Credit: Lee Jenkins, University of Missouri Extension.

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 formation of secondary roots. Also, extra rich soil near the vines helps rerooting.
  • If you can find the entrance holes and “sawdust,” try inserting a wire and thread 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 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. kustaki (“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!

Plants Affected

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Reader Comments

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My solution for Vine borers and Squash bugs

I have been gardening since I was 22 and I am now 59, never have I seen this problem like this before. Last year was the worst yet so far. My friend slit the stem and found two huge ones. I on the other hand have no patience and just uprooted and started over again. I did read if you take a rhubarb leaf and wrap it around the base of the plant, well that worked but I also think it worked because I killed most of the ones in my garden already. But I got some zucchini, not much but I did. No cucumbers at all. How did I kill them, eggs too, your going to think I'm nuts but I got a propane torch used for plumbing. I go out there and if I find anything that resembles a stink bug, wasp, even ants I burn the suckers. Eggs that are on the back of a leaf I break it off and burn the eggs. My neighbor and I bought nematodes about 30 million of them and let them loose, we couldn't really tell if it worked, not really with the gnats. The gnats and the vine borers killed my honeydew melon and they were beautifully plants. So, this year, we have many gnat traps, more nematodes, will try again the rhubarb leaves and the foil and I have some netting too when the seedlings are young. I will always use my trusty propane torch to burn beetles, June bugs, ants, leaf hoppers, you name it. The ants actually run from me anymore, lol... I light the torch as soon as I get into the garden early in the morning and I have burned a few while they were sitting on a leaf. They can't lay eggs if they are fried, they can't fly. I then pick them up and put them in the garbage and that's it. Oh, and this year we are tilling the garden. My neighbor likes to leave old dead plants from last year in the garden, but we got rid of them. No more big flat rocks or boards either. Don't know what happened that these bugs are just out of control and where did they come from. We need to have an immigration law against this bugs from hell, our food is at risk.

You made me laugh, its "Just" what I needed dealing with this

Thank You!
Its odd though~Years ago when we grew zucchini we had so much we couldn't give it away. And now~ Most of us are lucky if we even get any. I wonder why???

I started my pumpkins in the

I started my pumpkins in the greenhouse until July 14th. Thought I was safe here in south Jersey. But no, I just caught two moths today, August 5th. Obviously, we have a second hatch here. Yuk....

I'm from Central NJ and

I'm from Central NJ and planted yellow crookneck squash in mid-July. I saw three adult squash borer moths on the plant in late July (managed to kill one). Today, I saw evidence that squash voter beetles have been damaging my squash plants. I pulled one out so far and am debating what to do with the other one. My garden has been a disaster this year, from downy mildew to wilt to being overrun with cucumber beetles to something killing all my pepper plants and now this. It is enough to make me think about giving up.

This is the first year that I

This is the first year that I didn't see a sign of Squash Vine Borers in my zucchini or acorn squash. I tried something different this year.
After they started to vine out pretty good I injected the stems with a Thuricide mixture. Then I started spraying the stems with Liquid Sevin, especially the lower stem where it comes out of the ground. As the vines got longer, I sprayed the main stem further away from the ground too. I sprayed every time after a good rain as well as once a week.
I figured, when the egg hatches and it starts to bore into the stem, it had to go through the Sevin, therefore, it would die before it got in the stem. Maybe it was just coincidence but I never saw a sign of borers. After the end of August I stopped spraying.
Don't spray the flowers with Sevin! It will kill the bees and other pollinators. I use Thuricide if I want to spray the whole plant to prevent bugs from eating the leaves.

Have you thought what all

Have you thought what all this spraying and injecting might do to what you eat?

I do not like to introduce

I do not like to introduce poisons into my soil as it kills beneficial organisms, and earthworms. You can wrap the stems with foil when the plant is young. I tried hilling the soil around the stem to prevent the moth from laying eggs there and so far it has worked on my winter squash. Then comes the squash bugs.

My pumpkin leaves began

My pumpkin leaves began wilting and fruit stopped growing. I saw the orange stuff coming out at the base of the stems, by the roots and saw holes so I figured bores. I took a blade to them this morning and cut out long, vertical sections out and found bores in every vine. All but one looks like it has been infected. I covered them with soil and watered heavily. We'll see what happens. I figured I either saved the plants or more likely killed them faster than they were already dying.

Well, we are going to get a

Well, we are going to get a total of 9 pumpkins from our 8 seeds planted. The borers definitely hurt our crop. After I cut them out, the vines kept growing for a while, producing a female here-and-there. They eventually starting dying, turning yellow and brown. They don't look pretty right now, but we did get some results. Most are pretty small though. I also had to deal with cucumber beetles and a lot of mildew due to the wet summer. All three problems occurred for our first year of growing. Hopefully next year will be easier.

this year I decided to try

this year I decided to try giant pumpkins again, not for competition just local fun. but when I was looking for something to spray or drench the pumpkins, they miss informed me about their product killing vine borers. wiped out one plant, finally tried some Malathion 57%. it actually says it kills vine borer. I had some success with injecting the spray with cattle syringe and large needles, it does kill the worm fore sure, but no way on knowing how many I missed. I will try the nematodes next spring. I use to use this professional spray called WARRIOR T OR Z, but unless u know a commercial friend sprayer its almost impossible to buy. its deadly and all the giant pumpkin growers use this. very pricy, but hey it works. just have to be carefull when u spray. in my area , we've had no bees for a few years because of aerial crop sprayers, this is the first year I've seen some in my patch. after my pumpkins are set that I want to keep, I cut off all the flowers to help keep the bees away.

IS there one source of

IS there one source of nematodes better than another? this will be a new and hopefully have great results using nematodes.

I have not had any problems

I have not had any problems with squash vine borers since I started using beneficial nematodes in the spring. Garden's Alive is the source I've used. They are called 'Grub Away Nematodes' - they are pricey but they work & should control the cornworms too. Unfortunately they do nothing for cucumber beetles!

Any good solid total kill

Any good solid total kill methods would be great to know, even if I need to wait till next year to replant. These pests (all 3 together) are killing everything I have growing!

The article is inaccurate.

The article is inaccurate. The eggs are laid on the OUTSIDE of the stem, singly, by the adult moth. They then hatch and burrow into the stem, where the larva grows. There are no egg masses in the stem, as larvae don't lay eggs. The larva later crawls out of the plant and into the ground where it builds a cocoon and emerges the following year as an adult moth.

VERY well put Pete Walrath! I

VERY well put Pete Walrath! I am having a bugger of a time and my whole crop is being taken down from 3 directions at once. Flea Beetles, Vine Borer, and Armyworms/cornworms. They took my greens, took my squash, and are working on my tomatoes and peas now. About the only thing unaffected is my strawberry crop which was extra small because of a large Spring seedling crop of tomatoes.

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