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.

squash-vine-borer-damage.jpg
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!

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Reader Comments

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all iris in perennial garden are infested w/ similar borer!

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.

Iris Borer

The Editors's picture

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, ¼-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. 

Squash Vine Borers

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.

stem borers

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.

Squash borers

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?

Squash Vine borers

Seminole pumpkin are resistant.

SVB

Also, With Yellow Crookneck Squash if you can keep it alive long enough it will off-shoot another plant. Mound soil on the “vine” where it will root. If the first plant is killed the 2nd one can still live or 3rd, 4th, 5th, etc. One year I had a plant with 6.

Squash Vine Borer Defense

The best defense I have found is to mound soil up the main stems as the plant grows. Renew mound after a hard rain.

Squash Vine Borer Defense

The best defense I have found is to mound soil up the main stems as the plant grows. Renew mound after a hard rain.

Row covers!!!

We have both yellow squash and zucchini for the first time in years. In the past, both were attacked by squash bugs and then finished off with vine borers. This year, new locations were selected and an inexpensive bolt of tulle was purchased to create 'row covers'. The 54" width was not enough, so edges were stapled together around some string and left over stakes provided support. Then, duck tape was used to remove some early squash bug eggs. Hand pollination is required, but we finally have enough for ourselves and enough to share. I felt strangely happy when I found eggs deposited on the outside of the tulle! The bugs gave it a good try!

So frustrating

Every summer since I moved to Western Massachusetts, which has been the past 6, my squash plants have been destroyed by these pests. I got one zucchini out of 6 plants a couple of weeks ago, and not one since. The plants still look healthy and blossoming, but aren’t producing; and have the tell tale “frass” on the stems where the vine borers have entered the vine. I’m wondering if I should replace the soil in my garden? Or, should I make container garden beds? It’s so disappointing to watch all of your hard work and money and time get destroyed by these little jerks!

Adults still active in late July

Zone 7/ OKC. I am still finding adult moths on my plants as of tonight (July 24th 2019) I was under the impression that the life cycle was limited to early summer but I lost all of my summer squashes planted in April/May and 3/4 of my cantaloupes planted in early July are already infested. I'm going to try the yellow traps next.

Yellow water traps don't discriminate

I also am experiencing the borer moths in Late July, in Northeast Massachusetts. I tried the yellow water, but only found five dead bees. So I won't be doing that again as they are definitely not my target

Vine Borers

Don't give up! Slice open the base of the stem and pull those little jerks out! Place them in a mason jar of water with some dish detergent, they will die. Then press the two side of the stem back together and bury it with soil. Your plant will feel better and start producing within days!

Spray bottle with dishwashing liquid

I reused an empty Bonide blossom hormone spray bottle (the large one) for use as an emergency bug killer. The spray nozzle has 2 settings; wide and narrow spray. Any spray bottle with an adjustable spray nozzle would probably work but it helps if you find one that moves a bunch of liquid with one squeeze...like a powerful squirt gun.

Using 1 tsp of Dawn dish detertent into a quart of water, I filled the spray bottle and keep it hanging in a spot that enables me to grab it while I keep my eye on the borer moth. Like how you would mount a fire extinguisher...easy to grab and right where it's needed.

Using the narrow spray pattern, blast the moth as soon as it settles on the plant. I get them about half of the time. Using a strong surfactant like Dawn can burn the plant, so don't go nuts and spray the whole plant. Rinse the soap off of leaves if you can.

Update: Killed another borer

Update: Killed another borer moth today.

The circumstances went against everything I've read about finding squash vine borer moths.
It wasn't early morning or evening when I found the moth...it was early afternoon, mid-80s, humid and sunny.
It appeared to be oblivious or indifferent to my nearby movement so I was able to take careful aim and kill it with one blast and another as it lay in the dirt.
The eggs weren't so much near the soil line and on the main stem, but they were everywhere...tops and bottoms of leaves, leaf stems, adjacent blades of grass...very random, except that the eggs were indeed laid individually.

Shape of moth at rest.

P.S.:
The shape of the moth at rest was like this:
Its wings were tight against its body, giving it a stout, oval shape.
It was about 3/4" long and maybe a little more than 1/4" wide.
The black/orange colors made it easy to spot.

Good luck!

Thank you

The Editors's picture

Thank you for sharing your experiences to help the OFA community. Sincerely, your OFA editors 

squash bores

I put tinfoil around the base of the plant, supposedly the reflection confuses the bore of entrance. Don't know where I read this years ago, but it seems to work!

Vine Borers

Here's something I tried last year that seemed to work well, so I'm doing it again this year. I am using glass head pins, the ones with the ball at the top of the pin. I put the pin in the crook of the stem going down in the stem, sometimes it will go through, but mostly I try to get it in to the stem. I put 2 or 3 in each plant. This way, if the vine borer has/does invade the base of the squash it won't really be able to grow due to the pin.

Now, if I can figure out how to get rid of the squash bugs, I'd be happy, and have squash!

Squash vine borers

I’ve also had the displeasure of the destructive vine borers in Huntsville, Alabama. I did move my plant location last year and had great results from diatomaceous earth. I stayed on top of sprinkling the powder on the squash plants after it rained. It definitely helped a lot. I’ve used it this year too, but we’ve had a lot of rain the last several days so the diatomaceous earth was washed off. I was working in my garden today and spotted one of the evil little moths! I’ll be checking my plants better tomorrow.

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.

Borers

So sorry about your dad. Wish I heard of borers, but I see they have ruined my zucchini. This was my first attempt growing it. Well next time I will be on the lookout.

Borers

My condolences on losing your Dad. He was no doubt a wonderful father who enjoyed teaching you about the wonders of nature & love of seeing things grow. I still miss my Dad after 21 years.

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.

Your homemade garlic insecticide

Please send me the recipe for your homemade garlic insecticide to use in injecting into the stems. We are hoping to try to prolong the plants lives to get some squash this season. We have tried DE and soap sprayed on the plants and soil when plants were planted and through out but the borers still got them last yr as well as soap sprays with and without Neem, and with Kayolin clay. I was able to keep a few alive but they still died without producing as many squash as we hoped.
Thank you and I look forward to your reply.
Cassie

Squash that isn't bothered by SVB.

Try tatume squash which is a good variety and isn't a host for the dreaded squash vine borer. It is a vining type so give it room or train it up a trellis. In the south there is still time to grow it.

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