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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I am in Texas, and we have several rounds of SVB assaults. This year, I have been more determined to defeat these suckers and check every day for eggs too. They have a satisfying pop when you crush them with tweezers. I don't get them all, so your method works great for the few that make it past me. I might try netting next year, but then I lose all pollinators.
This year I spent a fortune by building raised beds, filling them with grow bags and bagged organic raised bed soil so my squash won’t touch any dirt from the ground. It doesn’t work. It’s nicer and it’s easier on my back - when bending down to pick out all those borers and eggs. I want to stake them and so I’ll try the soil wrapped in burlap if I need to. GREAT ARTICLE! Thanks!
The post I read before this was your description of how to properly prune and stake zucchini plants. You say to put a stake in the ground at the time of planting and keep it staked up and lower leaves pruned as it grows. But then in this post you say to bury the stem along the ground to allow more roots to form to help fight off squash borer invasion. If the plant is pruned and staked from a young age it's not going to be possible to lay the stem across the ground once that stem is thick and mature and growing upright. If you try to bend it toward the ground it will break. I've been gardening for 45 years , ok, 46, and I don't prune or stake my zucchini plants and burying sections of the stem has been one of my go to remedies after finding squash borers. Also the idea of staking zucchini and removing the lower leaves would leave the most vulnerable section prone to attack - more open and easier accessed by squash vine borrowers. If they were spaced far apart it would be easy to check them but your recommendation of planting them only 1' apart What Would not leave enough room between the plants for a thorough inspection of each plant. Particularly with some of the heirloom varieties I grow that get massive in size.
You can either stake and prune zucchini at time of planting or you can let it sprawl so you have more horizontal stem along with the dirt to bury in the event of a vine bore invasion, but you can't do both, it's one of the other.
I live on the Eastern seaboard of the United States and vine borers are a very big problem and even with the most aggressive measures to avoid them and very thorough checking, it's going to happen it's just a matter of when. So I would much rather have my plants laying across the ground so I have that extra stem to bury in the event I need new roots after I remove a section of the plant that has been damaged or after taking out of vine borer. If it is staked and tied up that option is gone.
Yes, these are two different methods of growing them. So one you are staking and growing vertically (my preferred method) and one where if you're sprawling you bury the stem. There's no contradiction, it's just two different ways that's all. ~ karen!
Excellent article I too live in the coastal north east and these pests have actually discouraged me from growing one of my favorites zucchini. After reading this article I will attempt to grow them again thanks for the info.
I get 8in x 8in cardboard tubes left over from strapping rolls from work. They make it easy to hill up your plants to cover the base of vines. Excellent for tomatoes!
How on earth do organic farmers get rid of squash vine borers ? There has to be a better way to deal with the pest...sans individual extraction or chemicals...right?
This is the first time I am growing spaghetti squash and on a trellis to boot. They are growing great and today my bubble burst as I have extracted almost 10 squash vine borer larvae (and sadly, I still have 4 more spag squash and 4 zucchini vines to check). One vine was hit pretty hard. Originally, when I transplanted it from the pot into the ground, the vine split a bit and I put floral stem wrap on it, but I really should have just dug it up and thew it out. That vine was hit the hardest. I have at least 3 nice squash growing on it, but the lower vine where I did surgery is pretty mangled (I don't know how the squash were getting nourishment!). The problem that I face now is how to "fix" the most mangled part of the vine. Since they're growing vertically, I can't put the mangled vine in dirt. I'm toying with wrapping it in some moist gauze and put it in between two popsicle sticks and stem wrap it shut to see if it will regenerate or just die. Another part of me wants to come up with some sort of way to suspend a plastic pot with dirt on the trellis and hope that it heals itself/sprouts. I will NEVER grow spaghetti squash again!
Hmm. I'm pretty sure you cant' do this, otherwise you so would have, but if it's possible, I would pull the vine down off the trellis and lay it on the ground, burying the broken part of the stem under soil. If you can't do that then I'd just tape it up and hope for the best. ~ karen!
Maybe a thin tube of burlap filled with a nutritious compost soil mix wrapped at the most mangled areas.??? Lighter than a plastic pot, can still be supported by the trellis and allow for water and air. Just trying to think outside the box.....JW
i hate borers. they've killed my zucchini, squash, cinderella pumpkins, watermelon. i'm obviously stubborn but they're more cunning. i read once that the best defense against borers is to just buy your squash at the store.
This year I'm trying again with zucchini and spaghetti squash. We'll see...
This method works great. You just have to remember to keep an eye out for them. ~ karen!
Thanks for the article, it's nice to commiserate with others about these lil' effers. They have been the bane of my squash growing for several years. I read that one way to control them is to try injecting either BT or neem into the vines, which resulting in me spraying my face with BT, and swearing off blue hubbards for life. This year, I found a resistant variety (Seminole Pumpkin) that seems to be doing really, really well, with no maintenance from me whatsoever. We'll see how they taste!
I feel like I'm the only one at my garden who struggles with these things! But I think I just grow more squash than anyone else. :/ However, they're all still alive and vines are all still doing well! So cutting them out really does work. It's just a pain and gross. ~ karen!
Those little twat waffles! I went away for 4 days and came back to an almost completely dead pumpkin patch.
I had 2 pumpkins that were ready to harvest, one that had been bored completely through, and one that’s still on the vine that I, hopefully, saved.
I really appreciate your garden tips and especially how you demonstrate what you are talking about.
Luckily the day I did this particular vine I got what was the best example (huge) of a vine borer I've ever seen! ~ karen
I followed your instructions last evening...my zucchini plant stem looks exactly like your photo. Worked like a charm. Didn’t have camera out there to take a picture. But, out popped the icky, ugly borer. 40yrs. of gardening & I never knew to do this. Thanks... big thanks!
Oh! That's great! I mean, it's gross, ... but great! I'm glad you found one and it worked. :) ~ karen!
Karen, this year my pumpkins had a gray bug that looked like a stink bug. It coated the posts that I had trained the pumpkin vine with their ugly bodies and left thousands of eggs on the leaves. I finally gave up and pulled up the vine hoping it doesn't spread. Have you ever had those?
Hi Peggy. Those are squash bugs. To deal with them you squish them. I also remove any parts of leaves that have the eggs underneath. I just tear that portion of the leaf off, fold it in half and smash it. It sounds like yours were officially out of control! ~ karen
I got the squash bugs! I have heard they stay in your soil and you can’t plant squash there again. True or old wives tale?
You are supposed to rotate crops every year (or every 2-3 years if you don't have a particular problem with pests) exactly because of that reason. So you should move your squash to another part of the garden if you can for a couple of years before you rotate back to the squash infested portion. It's a garden though so there are always going to be pests and disease. Some years are worse than others for certain pests, they go in cycles. That's just the way it is. You'll never completely eliminate them, you just have to learn to live with them - which can be done! :) ~ karen!
Yikes!! I'll be out looking tonight. Thank goodness my faves are Honeynuts, but I have a zucc making beautiful golden fruits just ready to pick.
well damn and blast. I finally have a zucchino (yes, single...I'm the only person in the world who can't seem to grow the bleeping things) after the first one got eaten by something in infancy. This post reminded me to go out and check for the ickies. The zucchino was the perfect size so I picked it (cue: Snoopy dance!) and then I noticed the signs of....And lo! the 3 disgusting buggers in there had eaten through enough of the single stem that it broke off as I was extracting them. ONE ZUCCHINO today! Tomorrow...the farmer's market.
GREAT ADVICE! You really got it together, girl. (Even when you make me want to spit like when I see pictures of you like last post looking all fresh and very pretty and fit and well, that's just wrong!)
Will this wee beasty also attack my prized zucchini?? Horrors! I will check for them this morning. Also is it better to twist or slice the zucchini from the plant?
And yes the borers do have a certain resemblance....
As a veteran of the Borer Wars I have come up with the perfect battle plan. I run up a white flag and quit. The result of all the digging and squishing and swearing never seems to add up to more than a few extra squash and well.....it's freakin depressing. So now I go to the farmers market and PRETEND that next year I won't have this problem. (The river running through my garden is deNile.)
Lisa mc.... you are hilarious. Truly. Same humor as Karen. And, did I mention wise? You are very wise.
can that be the cause of my cantaloupe vines dying? I will have to go check that. Thanks Karen.
Aside from the dirt, now you know why I don't have a garden.
I wrap the stems in duct tape after I find and kill the worms. Thanks for the reminder to check my squash!
White, maggoty creatures boring into...
Look around for orangey gunk...
This seems like you created a post specifically about metaphorical warning signs of the so-called ruler of the United States (scrotus). You did that on purpose didn't you? You slick fox, I love you... biodegradable glitter-bombs in the garden !!
Almost caused expelling of coffee onto monitor!
twould be funny if it twern't so true.
Have to go check my one and only zuke plant for signs of the dts. ugh
Subhuman commie faggot