Squash Vine Borer

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Squash Vine Borer

Here are tips on how to identify, eliminate, and control 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 is the squash vine borer.

The plants wilt because larvae is boring within the lower part of the stems. Look for holes and green to orange-yellow sawdust-like frass (droppings).

They attack squash, zucchini, pumpkins, and gourds. They prefer Hubbard squash and are not as fond of butternut squash. Cucumbers and melons are not usually an issue.

The borers overwinter in soil as pupae in cocoons. When the adult clearwing moths emerge in early to midsummer, they lay eggs singly or in small groups at the base of stems. The eggs will hatch within 1 to 2 weeks after 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, there is 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.

How to Identify Squash Vine Borers

The eggs are tiny, flat, oval, and brown. 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.

The adult is a moth about ½ inch long that looks a bit like a wasp with a black body, marked with orange-red. The hind wings are transparent and the front wings are metallic green.

How to Control Squash Vine Borers

  • Sometimes the best solution is to start your squash as early as possible. This way you'll be harvesting before the summer time when vine borers become active. If you plant early, you may need to be prepared to cover your plants in case of frosts.
  • Do not plant squash in the same bed two years in a row. Squash vine borers overwinter in cocoons in the soil. Also, clean up ALL debris and clean up your soil in the fall.
  • If you catch them VERY early, you can manually remove the squash vine borer. Slit the lower stem lengthwise with a fine, sharp knife to remove the larva by hand. Gardeners can make a vertical slit in the stem with a sharp knife and manually remove the larvae. One plant can house several. Then cover the slit stem section with moist soil about the point of injury to promote formation of secondary roots. Also, extra rich soil near the vines helps rerooting.
  • Or, if you spot entrace holes and “sawdust,” try inserting a wire and thread through the stem for some distance to kill the inside larvae.
  • If possible, catch and destroy the moths at twilight or in early morning when they are resting on the upper side of leaf bases.
  • There are insecticides, too, but timing is critical; they are effective when applied at the time that eggs are hatching. The biological insecticide B.t. (Dipel) can be injected into the squash stems, however, it is not usually effective because the larvae are protected inside the plant. Many find carbaryl (Sevin) to work. See your local garden store for advice on appropriate chemical controls. 
  • Preventative measures include covering the stems with a barrier, such as strips of nylon stockings, to prevent egg laying. 
  • Trap the adult orange moths with yellow sticky traps and yellow-colored bowls of soapy water.
  • Importing parasitic wasps prior to the egg stage can be helpful as these wasps are the borers' natural enemy.
  • One of the better solutions is to cover crops with floating row covers to prevent egg laying (but only if you are sure there aren't pupae overwintering in the soil). You can also drape these row covers over frames. This will not only give you a head start over pests but protect your plants from strong heat and frost.
  • A trap crop of very early-planted Hubbard squash can be used to alleviate pest pressure on other squash.
  • As soon as the squash is harvested, get rid of the vines. Till the soil in the fall and spring to get rid of overwintering pupae.
  • If you give up on zucchini, which is susceptive to vine borers, try growing a squash that's less resistant such as Cucuzzi (Lagenaria siceraria), also known variously as the snake gourd; it's pale green and twists and spirals like a snake.
  • Plant extra squash for the pests! They are around for 6 to 8 weeks and can only eat so much (or, so we think!).

See our Squash & Zucchini page for more plant care tips.



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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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