Are your squash plants wilting and dying for no apparent reason?? Yeah. There is an apparent reason for that. The dreaded squash vine borer. Here's how to get rid of it and save your squash plant from imminent death.
Skip right to the Squash saving steps.
Around the middle of July squash vines go nuts. They are vigorous, manic freaks that will take over and take hostage anything in their path. This includes rabbits, snakes, voles and tweens.
Actually more than taking them hostage the vines hide them. NOBODY wants to walk through a squash patch in full vigour because who KNOWS what's hiding under those leaves. However, if instead of shooting out new growth at an alarming rate, your squash vines are starting to wilt like they need water (even if they don't) you have a pest that's hidden itself INSIDE the plant.
Table of Contents
What are Squash Vine Borers?
Squash Vine borers are disgusting, white, maggoty creatures that burrow into the stem of squash vines. The pests overwinter in the soil and when the time is right in the spring they emerge, turn into moths and proceed to lay eggs at the base of their favourite plants; squash, zucchini and pumpkins.
The eggs are laid on or around the base of the plant and when they hatch, the squash borer eats its way into the squash stem, just above the soil line.
Once inside the stem, the squash vine borer continues to eat the inside of the stem hollowing it out until the plant eventually wilts and dies a surprisingly rapid death.
What the moth looks like
The vine borer doesn't start out as a digusting maggot (although it really is that whole what came first, the chicken or the egg conundrum). The squash vine borer is a black and orange moth that actually looks more like a fly or a wasp. Adult moths are active and emerging in early to midsummer so keep an eye out for them. Then squish them and kill them with all of your might.
You can try to trap them before they have a chance to lay eggs by using pheromone traps or yellow sticky cards. If you don't catch them and eggs hatch you have to move onto other control measures.
Will diatomaceous earth kill them?
Diatomaceous earth is the go-to for pest control among the organic crowd. If the gardener uses oak milk, there is a 100% likelihood they also use Diatomaceous earth.
But will it work? Diatomaceous earth is finely ground aquatic microorganisms. It's a fine powdery substance sort of like flour but because it's made out of ground up skeletons on a microscopic level it's very sharp. (the skeletons are made up of silica)
Because of the sharpness, when bugs walk or crawl or slide through DE the sharp silica slices through the pests. This results in not immediately but eventual death.
HOWEVER Diatomaceous earth is least effective on things like caterpillars, worms and slugs.
Therefore, sprinkling Diatomaceous earth around squash plants isn't likely to kill squash vine borers.
Also, DE is rendered useless once it gets wet so you can't water or expect rain for several days if you want to see any of its advantages against other pests in the garden.
ps I am a member of the organic crowd but I test methods to make sure they actually work rather than just assuming they will.
What insecticide to use
Just say no. Honestly. If you can just say no to drugs that'd be great.
However, if you want, you can try using Bacillus Thuringiensis (otherwise known as BT), a naturally occurring bacterium that kills caterpillars and maggot-like things.
I've never used this method but this is the year I'm going to do a trial run of it on one plant.
BT is normally sprayed on the leaves of plants to kill any caterpillars that feed on them. The problem with squash vine borers is that they live on the INSIDE of the plant. So how do you spray them? You don't.
You inject BT into the base of the vine where the squash vine borer lives.
To Kill Vine Borers with BT
Apply treatment just after flowers start to bloom on the squash vines.
Fill a 3cc needle syringe with 1 ml (cc) of liquid BT.
Slowly inject the BT into the squash vine 1 - 1.5" above the soil line.
Remove the needle and syringe from the vine and then flush it out with a 10% bleach solution to clean out the BT and kill any possible bacteria.
Shop for the stuff:
3cc syringes and needles are here and premixed liquid BT is here.
Identifying Damage
In the mess and tangle of squash vines, it's easy for vine borer damage to go unnoticed, so you have to make a point of looking for signs around the end of June and beginning of July.
I have the most problems with my winter squash, but summer squash, pumpkins, cucumbers, and melon scan also be affected.
Signs of squash vine borer activity are:
- Mushy main stem that feels hollow when you squeeze it, instead of firm.
- Holes or cracks in the stems of the squash plant, near the soil line.
- Evidence of yellow fluffy frass (squash vine borer poop) around the soil line and on the stem. It looks kind of like sawdust.
You can see the 3 spots on this one large squash vine that vine borers have gotten into it. Anything circled is a vine borer hole. Anything highlighted slightly in red is where the vine will die. Basically it'll die from the point of the hole straight out.
Since vine borers make their entry points at the start of the squash vine where it meets the soil that basically means the entire vine from that point out will die taking all the potential squash with it.
So what do you do?
You have to cut those suckers out. You have to lance the wound.
Just because you can't see the vine borer hole doesn't mean you don't have them. They're often on the underside of the stem so there's no visible evidence of a hole.
In that case look around the soil for orangey gunk. That's squash vine borer frass (poop). If you see it. You have squash vine borers.
And again, the easiest way to check for vine borers is to squeeze the stem near the soil line. If the stem feels hollow, you have a vine borer.
Yup. That's just how gross they are. So to reiterate:
Squash Vine Borer Prevention and Control
How to organically control Squash Vine Borers in your garden.
Tools
- knife
Instructions
- Look for evidence of wilted leaves or stems. If you have them chances are you have squash vine borer.
- Check all around the stems of each plant for holes or frass (orangey poop)
- Feel the stems near the soil. They should be firm not soft.
- Slice into the stem with a knife where it is hollow and look for the vine borer. Extract it.
- If you can’t see the vine borer, scrape your knife back and forth inside the vine until you’re sure nothing could have survived. You’re trying to squish/kill the vine borer inside the vine.
- Cover open wound of stem with soil.
Notes
- Check your vines even if your vines aren’t wilting. Catching the borers early is key to success.
- While your plant is growing earlier in the season, push your vines towards the soil and hold them in place with a mound of soil on top, or a U pin. This will allow the vine to root there, helping that portion of the vine survive a vine borer attack at the main stem.
- Grow vine borer resistant varieties of squash. Butternut and Honeynut are two that seem to be less vulnerable to vine borers.
- You can try to kill squash vine borer as soon as possible by injecting BT into the stem of the vine 1-1.5" above the soil with a 3cc syringe and needle. This needs to be done in late June, every 10 days until the end of July.
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TIPS
- Check your vines even if your vines aren't wilting. Catching the borers early is key to success.
- While your plant is growing earlier in the season, push your vines towards the soil and hold them in place with a mound of soil on top, or a U pin. This will allow the vine to root there, helping that portion of the vine survive a vine borer attack at the main stem.
- Grow vine borer resistant varieties of squash. Butternut and Honeynut are two that seem to be less vulnerable to vine borers.
Preventing Squash Vine Borer Damage
- Grow borer resistant varieties of squash like Butternut or Honeynut.
- Clean up all of your squash vines as soon as you pick your squash.
- Rotate zucchini, pumpkin and squash beds. The cocoons overwinter in the soil so moving to a new location should help eliminate chances of them being born right next to your plants.
- If you plant in a bed that you're fairly confident doesn't contain any cocoons you can cover your squash plants with row cover. This will prevent the Squash vine borer moth (Melitta curcurbitae) from laying eggs on the stems.
- Mound soil or mulch up high around the stem of your vine as it grows to prevent a moth from laying eggs there.
- Wrap the main stem with tin foil, a plastic bottle or anything else to cover up the stem and keep it safe from a moth laying eggs. (I personally find this method to be a bit iffy, but others swear by it)
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After finding a borer already in a zucchini stem and removing it, I covered all my squash plants with floating row cover to keep the moths out. About the second week of July, when there were blooms needing pollination, I removed the row cover. Kept out beetles as well.
I HATE squash vine borers and wine coolers! They killed my beautiful Harvest Moon winter squash last year. (Borers, not wine coolers.) I tried to remove them but my intervention was too late. This year I am trying the wrapping method. I have moved my squash to new beds and I dug down in the soil and started wrapping the stems with that stretchy athletic bandage material. (AKA vet wrap in the veterinary world.)
I am ashamed to write this. I also used Sevin dust. I applied a small amount around the stem on the soil. It was not a windy day, there were no flowers on my plants yet. The idea is it kills the larvae before they get into the stems of my plant. Or I could be killing half of the pollinators that visit my yard and I will have nothing grow in my garden this year but zucchini and some acorn squash. That will be my gardeners punishment for the Sevin dust...
You'll be lucky if that's your punishment - I mean it's better than the other possibility, a thumb growing out of your forehead. As long as you know when to check for the borers, and do it on time cutting them out really works, so even if you applied Sevin AND tape, still check to make sure. Good luck! ~ karen
What about covering the soil with remay,and making a slit into it for the zuccinni to grow up through. Then perhaps when the plant is well on its way but before the moths come, perhaps tape tinfoil down to the remay on the ground, and extend it up the stem until it hits the first branch. How far can those vine borers climb up? Can they chew holes through tin foil? If the remay goes out two feet in all directions from the zuccinni, will the moth still lay her eggs? Is that too far for the vine borers to travel? I think I would partially bury a strip of metal at the edge of the remay to prevent the borers from travelling under the remay to the plant. How about making a collar out of plastic bottles, and coating it with the sticky stuff that people paint on trees to prevent nasties from crawling up the trunk, or covering the outside of the bottle with the sticky traps you mentioned? I suppose the sticky goo can be painted on the tin foil instead, if the moth is smart and sneaky she could fly down the plastic collar and lay her eggs in the soil inside the collar! Although I suppose her way could be blocked with something stuffed inside the collar snugly up against the stem. Has anyone tried either covering the soil, or preventing the borers from climbing up using sticky goo painted on something they can't bore into? I have never grown zuccinni or cukes or melons before, but all are on my list for this summer. This article has me scared! My garden is so small it would be a tragedy to lose that amount of produce after all of my hard work.
Hi Neely! Yes, some people protect the stem by putting a tube of some sort around it like a collar. The only problem with that, is if a vine borer *does* get between the collar and stem you can't see when it's doing damage. Honestly, as long as you check for damage around the end of June/beginning of July you'll find the vine borer. :) ~ karen!
I need help with squash bugs, not borers. I’ve tried planting marigolds & nasturtiums, using DE & neem oil, and even grabbing the suckers and throwing them into a bucket of insecticidal soap. I’m at my wits end! Any tried and true remedies?
I’ve heard a shop vac will get them then just dump them into your burn barrel and light them up. I plan on trying it this year since nothing else I’ve tried has worked.
Planting radishes as a trap crop around cukes, squashes etc. really seems to keep the squash bugs away. I tried everything years ago including encasing my plants in row cover bags that I made myself.
The radishes do the trick. Plant a row a radishes inbetween every group of cuke/squash.
Good luck!
I just found a major infestation and had to rip the whole zucchini plant out. Any recommendation for something to do to the soil to prevent overwintering? Looking for an organic solution. Also, can I now plant something else in its place that isn't in the squash family?
I have this same question.
Answers?
No, there isn't anything organic that I know of that you can pour/spray on the soil the kill the overwintering larvae. BT will kill the larvae but they have to eat it and to do that you have to spray it on the host plant (the one that they're eating). ~ karen!
When injecting squash vines with bt, do you use concentrated or ready mixed?
Thank y’all for the comments and of course lessons. I’m ready to plant my Zucchini today so l will get a head start with my eagle eyes for those little varmints. Thank the Lord I’ve never had a problem before.
I dont have a comment box just a reply box I want to let this woman know I found the PERFECT FOOLPROOF prevention for vine borers. I used it last year & didnt loose 1 plant. You cut 6" wide strpis of tinfoil when your plant grows you put the strip around the base of the plant making sure you get about 3/4" under the soil and wrap the tin foil tight around the base/stalk of the plant. The vine borers can't get to the stalk also if you place a ring of it around your plant that helps to deter the critters. Pass the info on. I had a bumber crop last year with not a one borer!
Lucky you.. did this and the battle is still on for my plants!! Augh
I’m in North Central Texas and we get multiple broods of SVB every year. My approach to dealing with them is to just get squash growing as early as possible to harvest as much as possible before the borers destroy the plant. Most summer squash varieties seem to tolerate quite a bit of damage while still setting fruit. I avoid winter squash varieties that aren’t C. moschata (butternuts can produce even with svb damage). Lastly, I grow edible gourds (Lagenaria sp.) like Cucuzza that are every bit as tasty as summer squash that are SVB-proof. The borers don’t touch them.
Great article! I read that yellow bowls filled with soapy water and placed at base of plants will attract the beetles and they will drown. Have you tried this approach?
Nice article and thank you for sharing your experience.
Here is mine.
After fighting these bores for a few years I found this tip from an old and experienced gardener.
Grow your zucchinis after July. In most areas, the vine bore moth is gone after that date.
Plante my seeds 3 weeks ago and am growing them vertically and they do great.
Eddie
Yes! That works with a lot of things actually. Planting later than usual if you can. ~ karen!
Not an option if my growing period for squash is from June to September.
Hi Karen,
Thank You so much for this lesson! It wasn't until yesterday that my vines started wilting and I found frass in areas all over my Spaghetti Squash plants. I went after each borer using a straightened paper clip, which worked well to get each one out for the official and satisfying squish.
Excellent! ~ karen
Is there a way to kill any vine borers that might be overwintering in the fall/early winter, so that my prevention method next year isn't quashed by the ones that are in the soil?
Oh man! They got me....they got me bad!
They came in so fast. As soon as I saw wilting......
Just came inside from slicing and dicing and squashing cuke beetles!
Covered the vines with dirt but maybe I'll try the duct tape thing.
I have quite a few acorn squash growing. Hopefully this won't stop their growth. Guess I'll have to give this bed up next year.
Boy it makes me mad. If I wasn't such an avid gardener, I'd take a flame thrower to the whole area and eradicate those suckers!
These little buggers are going to make me seek anger management classes! Lol
Happy gardening all 😂
I was also trying to figure out how I can burn them out without setting the neighbors yard on fire too! Lol
I’ve had borers before, and started covering stems with foil when planting. This year, I had a summer squash plant start wilting at a few leaves, and found openings that look like borer holes at the stem right below the leaf (at the top). I pulled the whole stem apart & found nothing. The hole looked like a borer hole but at the top of the stem. Have you ever seen this? I pulled that plant out...hoping the other 4 are ok.
I haven't seen it, but I had another reader tell me the vine borers in her area were so bad that they did in fact enter from all over the plant. The stem at the base, and top. So it could be! ~ karen
In South Africe I suddenly found this "new" problem. They attack at any place on the plant, from the base to 3 foot up. Vitually no pumplins or cucumbers. I can not think that injecting the base will help?
Will it?
Hi Andre. You're right, it has to be injected where the larvae are feeding. But you can do the same thing anywhere on the vine (as long as you can find the entrance point or the area the vine is hollowed out. ~ karen!
Thank you Karin. I have only 6 plants to feed my family. One had 11 worms feeding and large parts died. Too much damage before we caught the buggers. Can I try and find or trap the orange moth that lays the eggs? When is it active?? Will the old fashioned paper glue fly hanger cois help??
Thanks Karen; I wish I had seen this last year. The little buggers killed my spaghetti squash plant before it had chance.