Perhaps among the most nefarious of squash pests is the squash vine borer. Identifying and preventing squash vine borer can save your squash plants from a sudden and disappointing death.
Identifying Squash Vine Borer
These squash pests are, unfortunately, tricky to discover before they do damage to your squash plants. The squash vine borer is both a winter and summer squash pest and will affect both types in a similar way.
A squash vine borer is a small, cream-colored caterpillar that inserts itself into the inside of a squash stem. They are difficult to see, as they are normally found inside the plant.
Is Your Squash Plant Infested with These Squash Pests?
If a squash vine borer has infested your plants, the result will be a rapid, sometimes overnight, decline of the plant’s health. Leaves will wilt and fruit will fall off the plant before it is mature.
Checking the base of the plant will confirm their presence. If it is squash vine borer, there will be a small hole and some sawdust-like residue at the base of the plant.
Removing Squash Vine Borer
Typically, by the time you discover that your plant has been infested with squash vine borers, it’s too late to save the plant. But, if you have been diligently checking the plant and see the distinctive holes at the base of the plant before the tell-tale wilt sets it, you may be able to save the plant by removing the squash vine borer.
The easiest way to do this is to wait until dark and examine the plant with a flashlight. The light will shine through the stem except where the squash vine borer is sitting. When you find the squash pests, either carefully slit the stem lengthwise and remove the vine borer caterpillar or use a toothpick or other skewer to pierce through the stem and into the vine borer. After either treatment, bury the vine at the damaged spot.
Pesticides — organic or non-organic — will not work after the plants are infested as the stem itself prevents squash vine borers from coming in contact with the pesticide.
Preventing Squash Vine Borer
The best way to control squash vine borers is to make sure you never have them in your garden. As with most pests, good garden maintenance is the key. Be sure to clean up your garden at the end of the year and dispose of any squash plants. If you have had a known infestation of squash vine borers, destroy all plants that were infected. Do not compost them.
Rotating squash plants is important as well. The squash vine borer will overwinter in the soil. This will help with preventing squash vine borer, as it will eliminate the host plants in that bed for next year.
Pesticides can be applied to the soil at the start of the season to try to kill the squash vine borer in the ground.
You can also try to use a squash vine borer barrier. This can be done by wrapping the base of the plant in a light, stretch material, such as nylon. This will prevent the squash pest from getting into the plant.
Preventing squash vine borer pests is the best control that you have when it comes to these annoying squash pests.
How to Inject a Squash Plant for Vine Borers
Squash vine borers infect and devastate a variety of plants from the cucurbit family, including squash, gourds, cucumbers, pumpkins and melons. These winged, red and black pests lay eggs that develop into tiny worms. The worms burrow into a plant's vine, suck out the juices and inject a toxin that causes the plant to wilt and eventually die. If you catch a squash vine borer problem early enough, you may be able to rid your garden of the pests and save your squash plants. Bacillus thuringiensis (Bt) is a strain of bacteria that is used to harm squash vine borers and other pests. Injecting Bt directly into a squash plant's vine is the fastest way to control the problem.
Watch for the first flowers to appear on the squash plant. Plan to inject the plant with Bt just after the first flowers bloom to obtain the treatment's maximum effectiveness.
Insert the tip of a disposable, 3cc hypodermic syringe into the opening of a bottle of liquid Bt. Pull back the syringe's plunger to fill the syringe with 1cc of liquid Bt. The syringe has a "1cc" marking on it.
Insert the syringe's needle tip into the squash vine stem about 1 1/2 inches above the soil line.
Push down on the syringe's plunger to inject the Bt into the vine. Push slowly so that the Bt doesn't leak back out of the injection hole.
Combine a mixture that is 1/2 water and 1/2 chlorine bleach in a bowl. Insert the syringe's needle tip into the water-bleach mixture, and pull back on the plunger. Push the plunger down to squirt out the water-bleach solution. Repeat the procedure, inserting the needle tip into the mixture, pulling back the plunger and pushing the plunger down to expel the solution. The water-bleach mixture sterilizes the needle and prevents the spread of disease. Clean the needle this way after each injection.
Repeat the injection with 1cc of Bt in about one week to 10 days.
- If your squash plant has an advanced vine borer infestation, inject Bt about 1 inch above each borer hole.
- It's also possible to remove the borers by hand. Make a vertical slice through a stem, but don't cut through the stem completely. Extract the borer worms with the knife, and throw them into a bowl of soapy water to kill them.
Melissa King began writing in 2001. She spent three years writing for her local newspaper, "The Colt," writing editorials, news stories, product reviews and entertainment pieces. She is also the owner and operator of Howbert Freelance Writing. King holds an Associate of Arts in communications from Tarrant County College.
Squash Vine Borer Management is Critical
Squash Vine Borer Management Strategies
This insect overwinters as a pupa, typically emerging as adults in mid-to-late June. The black and orange to red moths will lay eggs throughout July and August. The eggs are oviposited individually or in small groups on the stem of the host plant just above the ground surface. The eggs can take up to a week to 10 days to hatch. After hatching, the larvae enter the stem of the host plant, leaving a small hole surrounded by frass – a telltale sign. The larvae will feed while tunneling through the plant stems for about one month. This injury will cause wilting or sudden collapse of the leaves where the feeding occurs. Once the feeding is complete and they are ready to pupate, the larvae will burrow into the soil and spin a cocoon. They will remain in the soil until the following June.
Squash vine borers are challenging to prevent or manage. Once the larvae invade the stem, it is difficult to treat squash vine borers. Check your squash for the presence of adult borers starting the last week of June.
There are two methods for detecting squash vine borer adults. Watch for their activity in the garden. These moths are easily noticed as well as heard (buzzing noise) when they fly.
Use a container (e.g. pan, pail, bowl) colored yellow and filled with water. Squash vine borer adults are attracted to yellow. They will fly to the container and be trapped when they fall into the water. Place traps by late June, checking your traps at least once a day. Promptly pull and destroy any plants killed by squash vine borers.
Once the presence of squash vine borers is confirmed, pick one of the methods to control their population. Plan your planting schedule carefully. Plant vine crops that are usually not attacked by squash vine borers, such as butternut squash, cucumbers, melons and watermelons, as trap crops. Plant a second planting of summer squash in early July. These plants will mature after adult borers have finished laying eggs and will not suffer any damage.
Use a physical barrier by placing floating row covers over your vine crops when they start to vine (or for non-vining varieties, starting late June or early July) or when you first detect squash vine borer adults.Keep the barriers in place for about two weeks after the first adult borer has been seen.Secure the row covers in a way that prevents adults from moving underneath it. Caution: Do not use floating row covers anytime crops are flowering. This prevents bees from pollinating your vegetables.
If your crop is still successfully attacked by borers, you can try to kill the borer inside the vine. Keep in mind that you may not be able to save the plant. As soon as wilting is noticed, use a sharp knife to cut a slit in the affected stem. Slice carefully up the vine until you locate the borer (or borers).
Once you have killed any borers with the tip of the knife, mound moist soil over the cut area and keep this spot well watered. New roots may grow along the cut stem, allowing the plant to survive. Practice rotation to minimize this issue by planting cucurbits in different areas of your garden (if possible) or alternate seasons when you grow cucurbits.
If pesticides are needed, spray or dust the stems at their base.Start treatments when vines begin to run (or the last week of June or early July for non-vining varieties) or when the first adult borers are detected. Repeat in 7-10 days. Two applications help manage most squash vine borer adults. For more thorough coverage, continue treatments at 7-10 day intervals until the end of July. Common names of active ingredients effective against squash vine borers are: carbaryl, permethrin, bifenthrin and esfenvalerate.
Be sure that the fruit/vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.
Lack of water or vine borers?
What you may initially think is a plant drooping for lack of water, may be these pesky plant eaters. Typically squash and zucchini are affected and once robust leaves will suddenly be dropping.
How you can tell if what you’re seeing is lack of water or actually vine borers? Well, unlike a droopy under-watered plant, you may see a small hole at the base of your plant. Frass, or poop, from the vine borer will be crusted around this tiny hole around the base of the plant.
If you notice this crusty deposit, then chances are, you’re dealing with vine borers. But all is not lost! It’s still possible to save your plant from these spring and summer pests. But let’s first talk about prevention.
If you’re looking for natural pest control methods, then be sure to check out my book Natural Pest Control Methods for the Home Garden. It’s a great reference for treating all kinds of garden pests without harsh poisons!
Hole where vine borer entered the stem.
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I’m a part of a few local Facebook gardening groups, and as of recent, many people are posting about wanting to give up on growing squash altogether. They feel completely defeated by the squash vine borer after losing 50-100% of their crop. Squash vine borers can be quite the nuisance, but hey, they’re just trying to survive too…
I understand the struggle my fellow Facebook-users feel, as I myself have battled with squash vine borers since I began growing vegetables several years ago. I have tried so many methods to get rid of them! I’ve wrapped the bases of the plants with aluminum foil, sprayed with neem constantly, and dug out larvae from stems. My efforts have so far not been successful, but I’m far from giving up. I challenge you to also keep growing squash!! Every year is different, and in the worst-case scenario you rule out another method of controlling the squash bug that doesn’t work. Even “failure” is still progress!
What do you think? Have you dealt with the squash vine borer before? What tactics did you use to prevent/control them? Let us know in the comments!
Now for the Good News
The good news has two parts.
1. Do not despair! You can plant again.
In most regions, you can plant a second round of zucchini in early July and still get a good harvest later in the growing season. Act quickly if planting from seed. Better yet, check your local nurseries for leftover squash transplants.
From what I understand of the vine borer’s life cycle, squash planted later in the growing season like this (early July) should not be affected by this pest. By the time these plants mature, adult vine borers will be finished laying their eggs. Hooray!
2. Here’s the best part: vine borers are 100% preventable.
I’ll show you how we have successfully warded off vine borers in our garden for the past several years. It’s so easy!
If you lost some plants to vine borers, don’t beat yourself up. It happens to most gardeners at least once! Just don’t let it happen to you again. Be smarter than the vine borer, friends.
Are you ready for this? Here is the solution to vine borer trouble: Dixie cups.
Yep, all you need is one 5 oz. paper cup per plant. I’ll show you my simple method in the video below, or you can simply follow these instructions:
- We follow this method for all vining crops. Zucchini usually takes the hardest hit, but we play it safe by protecting melons, cucumbers, pumpkins, and winter squash too.
- Timing is important. Wait until seedlings are a few inches tall, but still small enough to fit through the cup. It’s also best if the ground is soft and wet, like after a rain.
- Remove the bottom of each paper cup. I like to make a slit with a sharp utility knife, then use my fingers to pull the round bottom out of the cup.
- Gently push one hollow cup around each seedling, carefully wiggling it down into the ground.
- That’s it! Leave the cup there all throughout the growing season.
UPDATE: Just yesterday, the very day before this blog post was scheduled to be published, we discovered vine borer damage to two of our otherwise healthy zucchini plants. Noooooo!
It’s ironic, because I had just asked Mr. Native Texan, What is it about the cups that keeps the moths from laying eggs on the stem? Couldn’t they still get down inside the cups? We weren’t sure, but for some reason, we’ve had very little trouble with vine borers since we started using the cups. So we shrugged it off. If it ain’t broke, don’t fix it.
Special thanks to my friend Rachel for snapping this picture of her dying zucchini plant. The very last picture below is also hers.
Well. Now that we’ve lost a few plants to vine borers, even with the cups, here are a few observations, preliminary conclusions, and a game plan for moving forward.
1. Peppermint Oil Garden Spray
We’re now pretty confident that our Garden Spray with Peppermint oil was making a much bigger difference than we realized. This year our zucchini crop is planted in an entirely different area of the garden. Because of the new location, it’s harder to access the base of the plants. In previous years, our squash was planted in raised beds, with a garden walkway directly behind the plants. That made it much easier to spray the entire plant, including the base of the stems. This year we also haven’t sprayed as proactively as we did over the past several years. You’d better believe we’ll be spraying future squash plants like it’s our job.
I don’t have high hopes, because we’ve tried it before with little success. But we’re a little smarter this time, with more experience under our belts, and really, what do we have to lose? We plan to slit the stems of any affected vines, locate and destroy those blasted little worms, and cover the surgery sites as best we can.
It’s still the first half of July, so we plan to plant another crop of zucchini if necessary. As I mentioned above, we hope to get around the vine borer’s life cycle by planting later in the season.
4. Stem Wiping
In my research to find effective, organic methods for vine borer control, I’ve come across a few intriguing ideas. Going forward, and especially beginning today with our Pumpkin, Spaghetti Squash, and Blue Hubbard Squash seedlings, I plan to wipe down each stem with a rag soaked in water and Peppermint & Thyme essential oils. According to my research, this should be done at least every five days but I plan to do it daily-ish.
5. Stem Wrapping
The Dixie cups were a good start, but we plan to take it a step further by wrapping the stem itself with a material like gauze bandage rolls.
6. Yellow Bowls
Apparently the adult moth is attracted to the color yellow (hello, squash blossoms). Much anecdotal evidence online shows some success in using yellow bowls of water to trap adult vine borer moths. Simply set out yellow bowls of water in the garden and the moths will fly to the bowls and then drown.
7. Tilling Under
According to Abby Seaman at Cornell University’s New York State Integrated Pest Management Program, affected crops should be tilled under immediately after harvest. Somehow this helps to prevent buildup of potentially damaging populations like the vine borer. I definitely don’t want these little buggers overwintering in the soil, so we’ll be following Abby’s advice.
You’d better believe we’ll be releasing the chickens in that area this fall and next spring. I hope they find and destroy every single larvae and pupae in the soil.
We gardeners are a resilient bunch, and now I am more determined than ever to outsmart these nasty vine borers with completely organic methods. Hopefully we won’t lose any more zucchini plants to the dreaded borers, but with two plants lost already, I’m not holding my breath. Time will tell. Stay tuned for updates on our battle against the vine borers!