Squash Vine Borer

How to Identify and Get Rid of Squash Vine Borers

Squash-vine-borer
Squash vine borer, by Massiv99: Wikimedia Commons

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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. The culprit is probably the squash vine borer. The plants wilt because larvae is boring within the lower part of the stems.

Squash vine borers 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.

Identification

How to Identify Squash Vine Borers

  • Eggs: The eggs are tiny, flat, oval, and brown. The eggs are laid scattered around the bases of squash and pumpkin 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 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.

identify-squash-vine-borer-moth.jpg

Photo Credit: University of Wisconsin-Extension. If you see the adult squash vine borer moth, beware that it is probably laying eggs!

Squash Vine Borer Damage

  • The leaves of the plant will probably start to wilt.
  • Look for holes at the base of the plant and green to orange-yellow sawdust-like frass (droppings).
  • Squash vine borers feed on the material inside the stems of the plants. The stem will rot at the site of the feeding.

squash-vine-borer-damage.jpg

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

Control and Prevention

How to Get Rid of Squash Vine Borers

  • 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 entrance holes and “sawdust,” try inserting a wire and thread through the stem for some distance to kill the inside larvae.
  • Sprinkle diatomaceous earth around the stalks when the squash vines are small. 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 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. 
  • 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.
  • Plant extra squash for the pests! They are around for 6 to 8 weeks and can only eat so much (or, so we think!).
  • An old folk remedy from The 1963 Old Farmer’s Almanac says that wood ashes were effective against the squash vine borer.

get-rid-of-squash-vine-borer.jpg

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

Prevent 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.
  • 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.
  • Preventative measures include covering the stems with a barrier, such as strips of nylon stockings or aluminum foil, to prevent egg laying. 
  • 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.
  • If you give up on zucchini, which is susceptive to vine borers, try growing a squash that’s more resistant such as Cucuzzi (Lagenaria siceraria), also known variously as the snake gourd; it’s pale green and twists and spirals like a snake.

Learn about the other main squash and zucchini predator: the squash bug.

Do you have any tips for controlling these pests? Let us know below!

Plants Affected

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Reader Comments

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SVB...Preventative Maintenance

So I’ve been on the lookout for these guys.
My Dad told me about them and his plight with the wilt they cause. While out in our garden, I spotted the little jerk, and sprayed it with wasp spray. After that I inspected all of my squash plants and removed around 40 reddish brown eggs. So I promptly put them in a bleach solution. I know there will be more. But I’m ready. This is my first year growing squash by the way. And sadly enough I’m doing it without my dad. He passed away 3 weeks ago today, before we could plant the garden. But it’s okay. His memory and guidance carries on. Good luck everybody.

squash borers

We had a severe outbreak of cankerworms 5 years ago and I used bacillus thuringiensis (A brand name is DIPEL) to kill the larvae on our plants. I also used it on my squash plants. Sprayed it on stems and leaves. My theory is that when the moth lays the eggs onto the squash vine, the egg hatches and has to eat thru the outside of the vine to get to the core. If the vine has well sprayed, then it ingests the bacillus and within hours stops eating and its gut explodes. Spraying my vines with bacillus thuringiensis works well if I am consistent with the spraying. Kept them going for 10 weeks one summer--until I missed spraying for 2 weeks and then the borers had their way. The bacillus is harmless to humans and pets and is a form of natural control of borers. By the way, control of cankerworms is only achieved with glue-covered strips around the trees on your property that host the female moths that crawl up them to lay eggs.

Vine Borer Madness

I've been gardening in Connecticut for over 40 years and for the last 20, the vine borers are a yearly battle. I have tried every method of prevention and treatment mentioned in this article and all the replies, but those dang worms win! This year I tried the "bait crop" method. Plant squash, wait until you see signs of vine Borer damage, i.e frass and/or sudden wilted leaves and then dig the entire plant out, getting some of the dirt around the roots and either immediately burn it, or put the affected plants in a heavy duty trash bag and tie it tightly at the top. The concept is that the borers will be eliminated in the larva stage and the life cycle is broken. Since we had snow and freezing temps into late April this year, I had to start my bait crop inside. I planted the seedlings (yellow crookneck squash) out the 3rd week of May and on June 15th I found frass at the base of several stems. Dug the plants out and before they got tossed into my fire pit, I did some investigating and slit open the stems from several plants. I was not prepared for the sheer number of borers each plant contained. My biggest plant, contained 56, yes 56 individual borers ranging from just barely visible in size to well over an inch. Every stem had borers, even those showing no signs of frass or wilting so apparently they enter in numbers through one hole then spread out into the various stems. Not only were they near the frass, but throughout the hollow stems and I even found some when I split open the thick veins on the underside of the leaves. No wonder my prevention methods didn't work, once hatched, these borers go into every root, stem and leaf vein the plant has..After carefully dissecting the first 5 plants, taking care to kill every Borer found, all the plants went into my fire pit. I planted a second crop, in a location I never grew squash before. The plants are just big enough to have blossoms now. I have been carefully watching for the moths and doing the best I can to inspect for eggs and of course it happened again..... Today there were wilted leaves so I slit the stems down to the soil level and sure enough, Borer larva , the*&@#!!!!! things!
So despite planting a sacrificial crop early in the year, burning the entire crop once larva were found, the second crop planted at least 100 feet from the first, and planted where squash had never been grown before, the 2nd crop got attacked by the same thing. This also confirms that the cold North East states get 2 hatches per year.. So despite my longing for home grown organic yellow squash, crop #2 went into the fire pit today. I'm going to plant a 3rd crop and hope our fall is mild enough that I get squash.
By the way, I've spent time every day looking for the moths and never seen a single one, so these pests are very hard to prevent and control. Not sure what I'll try next, but I refuse to use chemicals and I refuse to give up!

Squash Borers

Dear Lisa,

Your experience with the vine borers has to be most discouraging. I have been gardening for over 50 years but usually have not grown squash. Many years ago I had some excellent results with zucchini w/o any problems. So this summer (2018) decided to try Acorn squash. The plants were most robust and healthy but the next day they were totally wilted and dead as if something cut them off at the root.

After reading your impossible to win war against the borer and how the larva can winter over in the soil and how you tried to remove the borer by burning all the infected plants causes me to think why not burn the soil in which you are planting the vines.

Of course I realize you cannot burn an entire garden of say 30' x 40' (that is size of my garden). However, if you grow the squash in raised beds of say 4' x 4' (as I am also doing) or in large half barrels the amount of soil burning would be contained to a small area.

Start with a large gas (not gasoline) burner. Do the immediate soil surface first. Then turn over about 3 to 5 inches of soil and repeat the process. Do this about four or five times. This might burn (kill) all the larva in the soil.

You probably have been in contact with your local state agriculture office for info. If not check in with them.

Also saw a suggestion of placing diatomaceous earth around the immediate area the squash plants. In case you don't know diatomaceous earth is a very fine powder composed of the shells left by tiny marine creatures. It is often used in filters, especially swimming pool filters. The powder is so fine that it gets into the breathing system of insects cause irritation and subsequent death. In other words they seem to choke to death.

SVB solutions that have worked for me plus future options

I am not going to write too much because you never know if what you write is going to be published. First, there are many things to prolong the life of your plants that have been infected with squash vine borers. 1) Inject a homemade garlic insecticide into main stem of the plant with a syringe + needle. This worked for me when I injected every three days into zucchini plants that were infested. I do not think that the components of soap, garlic, and oil are going to poison me. They lived and produced fruit until the frost killed them. 2 ) For plants that spread out, such as pumpkin, cover each vine every two feet or less with soil and then water them heavily each time you cover a portion of the vine. Maybe do this once a week to correspond to your watering schedule. New roots will form at the locations where they were covered. The plant continues to thrive even if the plant dies at its original point of origin. This also helps if you have mildew emerging on the older leaves of the plant. Another option: How about breaking the cycle by planting only Cucurbita Moschata squash and pumpkins? If there are not many gardeners around you, this could be the trick. The squash vine borer can not survive inside the Moshcata family of squash because they have solid vines. I am trying this year Zucchini Rampicante (zucchini replacement), Waltham butternut squash, and Dickinson pumpkin (this a tan pumpkin like Waltham, but my kids will not care). All are Moschata and have solid vines. I do not know anyone else in my area that has a garden and plants squash. From experience, I do not believe any of the websites that say C. Maxima or some types of C. Pepo will survive the SVB onslaught. The only way they will flourish is by burying their vines every couple of feet or so and promote root growth at the buried vine. The following years I will plant different types so I can save their seeds.

squash borers

I've been told that planting nasturtiums and garlic in your garden will deter the squash bugs. I will give it a try this year. They get my zucchini every year before I do.

No on the garlic

My garlic was right by my zucchini and cucumbers, onions too. I will try nasturtiums.

Worse year ever for these disgusting things

I have been gardening for over 30 years and never ever had a bad zucchini crop. Well, I finally met the squash borer and boy did they go to town on my squash. First limiting the plants growth but I got one zucchini until I decided to look inside the stalk. I found one that was over an inch long and he feasted on inches of the stalk. Well I got so mad I pulled up all my plants and dug up the soil and found babies, look like little white worms and burned them with a blow torch. Also found tons of ants protecting their eggs and of course aphid eggs on the roots of my zucchini. The Northeast is getting a lot of heavy rain and I do believe this is the culprit also my friend leaving rotting and old plants in the garden from last year wasn't a good idea (no more of that). I also lost my cucumbers, honeydew melon and cantaloupe, so they do go after cucumbers. I have read a few articles and found the foil around the stem, but also using a rhubarb leave as a cover for the seedling (yes I am starting over) and will try this method too. We also got nematodes hoping they will kill the little ones as how can they get to the big ones in the stalk? We have Sevin too and will treat the soil with this as the little ones are the ones I am worried about now with the new seedlings I have. I like the picture of the moth, I thought it was just a regular white moth but now I know what to look for. The other comment from that man just didn't see the picture? Also there is a rhubarb tea that is poisonous that I will try in the soil. I will try anything now before the season is over, but next year I plan on turning the soil over, getting millions of nematodes not before I burn some wood right in the garden to add some wood ash to it and hopefully burn the little babies before they go hide for the winter. I will not let these little bas***ds ruin my garden. My advice is don't give up, get determined as home grown veggies vs. grocery store is well worth all the work and frustration. Don't let any pest ruin your fruit and veggies. Get a blow torch and burn them all, lol...

borer

Interesting Gloria, I live in the North East, Pennsylvania and lost my Zucchini and Gourd plants. What a disappointment. It happened so fast.

squash borers

We have lost several plants in years past to the dang borers!! Not anymore:) My husband is vigilant with his little shaker can of Sevin dust.
If it gets watered or washed away by rain, here he goes and sprinkles more. He keeps a little fine dusting around the stems (and up on the stems) of all our plants. NO borers. I am not usually so agreeable to using chemicals (in this case carbaryl 5%). But, we have tried everything else. This really works.

Hopeless

I did the manual "surgery" to remove the borers one year, and it was probably the most disgusting job I've ever had to do for my garden. Those worms wreaked havoc on my garden and even after painstakingly removing them they still kept coming back. I don't have the room to plant trap crops, nor do I feel they work as they just encourage more breeding of the bad insect.

This year I'm seeing the moths but I have no practical way of preventing them from laying eggs. Going to do what I did last time and use a systemic pesticide that both kills the borers and degrades into harmless compounds before harvest.

Try the Yellow Sticky Traps

I just found these on the web after hearing about them. The moth will fly onto the sticky side and get trapped. Also good for aphids and whiteflies. I just ordered some tonight and hopefully they will work. It said it attracts moths so I'm willing to give them a try. You can't give up.

squash vine borers

This is the second year I have had to deal with these monsters. This year I have been diligent picking the eggs off all my plants, (very time consuming) but yesterday I found 2 plants with evidence of the borers and had to pull the borers out - so I obviously missed at least 2, but probably more eggs. From my observations the moth lays the eggs on the top areas of the plant, I have found eggs on the tops and bottom of leaves, on the curly strings that catch the trellis netting, the leaf stems, bases of the flowers, and the plant stems, all mostly on the upper parts of the plants. Its extremely frustrating and heartbreaking to see the plants die after so much effort to protect them. In my search for a solution I did come across some netting for moths/butterflies - similar to deer netting in price and material, but it is NOT sold in the USA, at least not in a cost effective way. The UK and Europe sells the 'butterfly netting' for a similar price as deer netting $70/roll 7'x100'. Some companies here make something similar, but the price is triple or more; and to have it shipped from outside the US raises the price too high. This is the second time I have found solutions outside of this country that are available to other country's consumers - I can only think it has something to do with the chemical companies not wanting us to have organic options....very frustrated!!

Squash Vine Borers

Hi Vicki,

It sounds like you’re putting in a lot of effort into protecting your garden, and that’s unfortunate the butterfly netting is too expensive. Try going out with a butterfly catching net, or tennis or badminton racket in the evening. If you see any of the moths near or on your plants, capture and dispatch of them before they can lay the eggs. Each can lay over 150 eggs in its lifecycle, so stopping even one before it lays will do a lot of good. Also, next season try growing a more resistant variety of squash called Cucurbita maxima, which grows supplemental roots from its vines as it grows outward, allowing it to still produce squash even if the main stem were to die.

SVB

I know this is a year old so you may have come to some resolution by now, but I thought I would comment anyhow. I thought your comment was very observant. I live in north Texas and I have dealt with SVB for 4 years now. It is definitely a formidable pest for a home gardener. I grow organically and have tried all of the methods recommended by supposed agricultural specialists and internet advisers such as wrapping the base of the stem, manual removal of the larva by “surgical cutting”, hand picking the eggs, injecting BT into the stem, stringing a wire to impale larva, and row covering. Of all these methods, the only successful method by any means at all was row covering. Every other method fails for their respective reasons. Aside from row covering, planting early may be an option that would allow at lease some harvest before the arrival of the borer. I have done that before with a few zucchini coming off the vine before infestation, but in Texas, you have a much shorter time before temperatures warm up and the SVB arrives. Other than that, I have learned to grow varieties of cucumbers that they leave be. I am unable to grow pumpkins or winter squashes, gourds or anything of the sort. I do think there is some truth to what you say about some places making organic methods less pragmatic. Good luck to you in your garden.

What resistant varieties do you grow

What varieties do you grow that are more resistant?? Thanks! Kate

SVB

I'm in North Texas as well. Just realized all my acorn squash and pumpkins are goners. Sad. Thanks for sharing your experience.

inexpensive netting

I checked out my local craft store and toille is a very fine netting used mostly in wedding and party decorations. It costs only $1.25 a yard.

Netting

I've resumed my search again for a netting option. Last year I bought a bolt of inexpensive Tulle and covered all the squash. It was somewhat successful - the Tulle created other issues such as aphids and lack of air circulation because of the tight weave. The plants that did not get aphids were protected by the Tulle, but it started to disintegrate at the end of the season and rip easily. Its labor intensive to redo the Tulle each year as well as not very environmentally friendly to keep replacing it or economical for that matter. I still cannot find the 1/6" or 1/8" netting here in the states for a cost effective price - shipping doubles the cost from anywhere I have found it available. Does anyone have a connection in the USA for cost effective netting? China can deliver it, and its reasonably priced, but the minimum quantity is way too much for a non farmer!

netting

you can get 50 yards of the tulle wedding net 60 inches wide for about $20. Google for source

Squash borer.

According to the old farmer's almanac, what stage should we apply wood ashes and how do we apply it?

Wood Ash Ph

Yes, wood ash can affect soil Ph, sometimes for the better, sometimes not. It all depends on your soil so it is best to have it tested to determine if applying wood ash would be beneficial or harmful. We will try to get a pic up, but it is difficult to find any that are of the necessary size and quality. The eggs are tiny, flat, oval, and brown.

squash borer worms

I appreciated all the information and the way it was presented - both organic and inorganic.
Many options available. Next year I will try new soil (am a container gardener), laying down wood ash at the stem's base (anyone tried this yet since 1963? If so, what are the results?) wrapping vines with foil, hilling soil, then more wood ash. How will the addition of wood ash affect the ph of the soil? Any amendments to counter it necessary?
Thanks.

If possible - could you add a photograph of the eggs laid at the stems?

Wood ash

I don’t know about wood ash and it’s effectiveness for the borers, but here in Georgia a lot of people swear by it as a general way to keep away critters ( snakes, various pests and small animals)

I believe you meant " try

I believe you meant " try growing a squash that’s *more* resistant such as Cucuzzi" (not less) :)
Thanks for this article! Very helpful!

Resistant Squash

Oops, thanks for catching that, Hannah! We really appreciate it, and we’re glad you’ve found the article helpful!

successful and easy control of squash vine borrers

I have looked over many sites dealing with Controls for squash Vine borer. With a heavy infestation of these moths I have fought to protect squash using nearly all the suggested methods. Some work(complete netting of the plants) but are very labor intensive. Finally I watched the moths in the garden for many hours (letting them do their nasty work without disturbing them) and realized that they are extremely sensitive and careful when laying (THIS IS THE KEY TO CONTROL!!!!!). I then developed a much Less labor intensive method that seems to work Exceptionally well. Chopping hay in 2 to 4 inch lengths I let the hay lightly fall over the stalks, particularly the base, and even onto fruit to form a very open matrix. The moths will not land and lay, it appears to prevent landing of the moths. It's possible to walk through the garden and drop fluffy handfuls of chopped hay over any exposed vines every few days quickly and efficiently, apparently completely discouraging the egg laying. This is an organic method(Obviously) and takes relatively little time in a small home garden. If this approach is used Diligently it is nearly 100% effective. Anyone using the technique needs to make just a matrix of hay, Very open and loose, LIGHTLY ALLOWED TO DROP OPENLY, A HAND FULL AT A TIME (no need to put a lot) but with small enough gaps so that the moth is discouraged. The moths DO NOT LIKE CLOSED AREAS, THEY WANT OPEN ACCESS TO STALKS AND FRUIT - AGAIN, THIS ISTHE KEY). You don't have to pack in the chopped straw, just scatter it with most pieces looking like open "pick up sticks", that seems to be all that's needed. If you experiment with this method you will find it EXTREMELY effective and efficient. I've tried to spread the word on many garden sites but have not been successful, please share the idea. Call it the Mayo technique!

I am trying "The Mayo

I am trying "The Mayo Technique" next year on my pumpkin vines! These stinking pests are a real problem in WV, and after many approaches to deter them, my pumpkins are a complete loss this summer...just ripped my vines out and bagged 'em up. Grrrrr. I used to grow 100 lbs pumkins in NE Ohio with no sign of them. Here's hoping it will help me to grow that one big pumpkin I'm dreaming of for my little girl! Thanks for the tip! :)

The Mayo Technique

I am really excited to try this. It has been too long since I've had a home grown squash!! Is it possible to post a pic of your protected plants? This sounds really interesting!

Mayo Technique

Can you post a photo of this?

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