Guide + Action Plan for the LOATHED Squash Vine Borer Moth – With Additional Resources

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I Tried Everything. What worked and what didn’t, in my yard.

Bottom line. Cultivar, or the type of squash, matters most. The best strategy for limiting the damage of the squash vine borer -SVB- is to choose the types of squash most likely to survive their damage.

Squash vine borer moths are most likely to lay their eggs -and successfully bore into- a C.MAXIMA cultivar. Hubbard squash are the SVB babies absolute favorite squash to tunnel into and destroy. Next favorite cultivar is C.PEPO. In particular the yellow crookneck squash; borers hit it pretty hard every season. Which leaves my beloved C.MOSCHATA cultivar. The stems of these squash seem to be a bit thicker than other two types. So even when the SVB moth lays her eggs on a C.Moschata type squash (and she will), the newly hatched borers are far less likely to get into the stem and destroy the plant. Moschata squash types are also far more likely to survive a SVB attack. I recommend following the same strategies for C.Moschata that I set for the C.Pepo and C.Maxima varieties, just as an insurance policy and to ensure healthy plants.

My story had a happy ending. Although the Moschata cultivar plants were targeted and many eggs were laid on the stems, my Moschata type plants not only survived, but thrived. I raised a heavy crop, with Musquee de Provence squashes coming in double the listed weight.

C.Moschata for the win. And yes, I also had a lovely harvest of C.Pepo and C.Maxima type squash.

Let’s Discuss the Other Strategies and More About Cultivars

1. THE BEST DEFENSE AGAINST SVB IS TO PLANT C.MOSCHATA SQUASH.

How do you know the cultivar? Some seed companies will list the cultivar of the squash. Look for a note in parentheses or italics. Example below. For some rarer varieties, you may have to research.

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Great C.Elisabeth, but my favorite squash pumpkins are Maxima cultivars! What now?

2. TRAPS WON’T FIX PROBLEM, BUT THEY WILL HELP.

How does the trap work? The traps themselves are sticky traps, to hold the male SVB Moth. The traps come with a tiny lure in the same orange color of the moth. The tiny lure is placed inside the trap. The moths come to check out the lure, looking for a mate. Instead they get stuck and find death. YES! Can’t fertilize if you are dead. Additionally, the traps will tell you when the pests has arrived. Officially, the Squash Vine Borer moth will begin to emerge from the soil around 1000 Growing Degree Days. Last year the moths arrived at 850 degree days! The warmer your spring and summer, the earlier the moths will arrive. Every day counts when fighting a heavy infestation. While I follow Growing Degree Days, most gardeners do not, hence why traps are a good idea. Place them close on the ground, level with current squash blossoms, in your squash patch. Get um!

One note. While the traps do not bring additional SVB moths to my yard, it is technically possible they may attract more to yours even though I’ve never heard of anyone having that issue. I find they are only a help to me and those I know who use them. SVB moths find me easily without the traps and I notice fewer moths when I have the traps.

The traps I use. https://www.amazon.com/VivaGrow-VivaTrap-VT-100-Squash-Borer/dp/B0CNQDKSHC?ref_=ast_sto_dp

I know, terrible time to not have an affiliate program of any sort, I praise the @#*& out of these traps.

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3. FOIL HELPS A LITTLE BUT COMPARED TO THE PITA FACTOR…..?

The SVB moth will lay eggs on the foil. But foil protects, right? If the borers couldn’t crawl a very short distance, perhaps. I watched a video of an older gentleman that swore that only 2′ of foil from 1-2 inches under the soil to 2′ out prevents SVB eggs from reaching the stem of the target squash. Well, I have bad news for some of us. Alabama SVB moths are apparently far less motivated than the hard workers in my garden. I can haz lazy borer? I have found SVB eggs all the way at the end of 20 foot vines. I have also discovered SVB’s inside squash! Foiling all the vines isn’t practical and frankly doesn’t work that well, in my garden. It may very well work in yours.

Some eggs always seem to find their way under a loose section of foil, or the base of the plant gets exposed with watering. So I plan to just foil the base of the plant this year. Even though I find eggs throughout the length of the stem, the SVB moth does seem to prefer the base of the plant.

Consider time-cost with any method you choose. Plus regular old dollars spent.

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4. YELLOW BUCKETS OF SOAPY WATER DON’T WORK IN MY GARDEN

SVB are attracted to yellow! They’ll check it out and drown! If that works for you guys, I AM INSANE WITH JEALOUSY. But hey, try it. It must work for someone as I keep reading it as an effective strategy.

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5. APPLYING BT IS HELPFUL ONCE THE PLANT IS DAMAGED BUT OFTEN CANNOT SAVE THE PLANT, TIMING IS CRITICAL.

BT – Bacillus thuringiensis, is a natural insecticide that will degrade the borer from the inside once consumed.

BT generally needs to be applied more than once for an effective killing. I purchased industrial needles and injected the BT liquid into stems where borers were found. Then I buried the damaged stem if possible. Burying the stem may help save the plant. BT is messy. Healthy squash plants have many stems to treat. If you only have a few plants, this method may be more effective for you. The photo below shows small spots of yellow frass. You’ll find the SVB near those borer toilet spots. I inject the BT and coat the stems, to maximize potential benefit. Apply BT when the borers hatch and begin to tunnel into the stems, as the borer needs to consume the BT for it to be effective. BT does not kill the SVB eggs. BT is bee friendly as BT impacts the internal digestive system of a grub. BT is also injected into stem, and is not applied to flowers.

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6. COVERING THE STEM JOINTS WITH SOIL AND ENCOURAGING SECONDARY GROWTH DOES WORK!

NOTE: Not all squash are vining and produce roots/nodes. Most winter squash can, summer squash, less likely. Depends on variety and cultivar. This method can require strategic placement of soil, as the stem joints sprout the flowers and fruit to be pollinated. Leave the flowers and fruit exposed, mound soil over the rest. It can be time consuming and you will need a reserve of soil/compost handy for every applicable plant. Yet, I would say this is the most effective method of saving a plant from likely attack. Put soil over the stems as the plant grows, so if there is damage, there may already be rooting around the affected stem, allowing the plant to bounce back quicker. Waiting until you see the fat SVB, the frass and limp leaves is often too late for the plant. Bury the stems as they grow.

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7. CUTTING OUT THE BORER IS IFFY. ONCE BORER IS LARGE ENOUGH TO GET EASILY, IT’S DONE GREAT DAMAGE

That. Also, there is likely more than one. You’ll be doing a great deal of damage getting them all. That said, SVB population numbers differ between yards. This is a strategy worth trying if you don’t have a large SVB population, or only have one borer per stem.


Nothing to add but a photo.

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8. CHECK YOUR STEMS EVERY DAY OR SO FOR EGGS, AND DISPOSE OF THEM.

I actually plant my squash in a manner that allows room to sit and remove eggs. I like to be outside, thankfully. This a a tedious task, and in my case, keeps me mad because there are so many damn eggs!

Yet, thanks to being THAT meticulous means that I have collected a lot of data on these little beasts. I have a great deal of hands-on experience and am able to create, authoritatively, this guide for y’all.

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9. STAGGERED PLANTINGS WORK FOR SHORTER SEASON SQUASHES

Being a zone 4-5 gardener is limiting in this regard. Planting twice during the garden season of summer squash and perhaps a delicata or sweet dumpling winter squash might work in our zone. Unfortunately, those big pumpkins and winter squash? Either fall in love with Moschata types or take the advice I’ve given and godspeed for your fight.

I do plant summer squash in May and then again in August. This strategy keeps me in summer squash from July to October, and I can stress less about SVB prevention, leaving my resources to fight on the winter squash battlefield.

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10. ROW COVERS NOT EFFECTIVE HERE, BUT MAY WORK ELSEWHERE

Oviposition (egg lying) of the SVB coincides with emergence of the flowers and fruits. Bees love squash blossoms. I could cover the plant and hand pollinate. I tried this and the SVB moth still somehow found a way to lay eggs on my covered squash plants. The plant was in a pot, so no overwintered SVB in the soil, emerging under the covering. So I kept out the bees, but not the SVB moths. Perhaps you all will have better luck!

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11. NEEM DID NOT WORK

Neem was diluted, using the bottle instructions and applied every 1-2 weeks, depending on rain. Both neem with and without Azadirachtin was used.

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Can we prevent squash vine borers from emerging in the first place?

Fully? No. However, tilling in the fall and spring can expose the cocoon to death by drying or being eaten by predators. I have done this and still had a great deal of SVB’s the next spring. I am not anti-till, but I am anti-working my ass off doing something that results in nothing. So this year, no tilling for me. I DO encourage others to try it, if they feel it will help. As I repeat ad nauseum, my yard is not your yard. What works for me may not work for you, due to factors neither of us can fully explain. The variables number in the hundreds.

When you dispose of the affected plants, do not leave the plants in place to compost or save them, at all. Throw the plants away or burn them if you have a burn pile. The earlier you make the hard choice to pull the affected plant, the fewer borers will be left to overwinter and terrorize your garden next season.

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So you’d like to know more about the lifecycle of the Squash Vine Borer?

Me neither. But here we are.

The adult form of the Squash Vine Borer is the moth.

The adult SVB moths arrive from elsewhere or hatches from your yard where it overwintered in a small brown cocoon shell. Here in zone 4-5, begin keeping an eye in mid-June for the distinctive adult moth.

Unlike the squash bug, who lays her eggs in a symmetrical little group, the SVB moth will lay her eggs here, there and everywhere, one, two or a few per stem, in no apparent pattern. The eggs are copper colored.

In a week or so, the eggs will hatch and the very tiny borer will immediately begin to burrow into the stem of the plant. You can look for them while you are removing eggs from the stems, but they are hard to see.

Once burrowed into the stem, the borer will eat and eat and eat. About a month or so after the borers hatch, you will notice the telltale limp leaves of your squash plant. You’ll water, but it probably won’t help. You’ll take a closer look and notice the frass, the yellow/green excrement in little piles on the stem. You now know what this means. The squash vine borer is now a fat grub. It’s eaten away the vascular system that keeps the plant alive. Your plant stem is split and there it is. The plant’s death sentence has already been signed.

You’ll miss some borers as you do plant clean-up. They have already nestled into the soil, or they are hidden in the stems of the plant. They will settle into the soil, pupate over the winter, and start the fun all over again next season when they emerge from the soil as adult moths.

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So how did the 2021 garden season end for the C.Pepo and C.Maxima cultivars I grew?

AMAZING. They did produce! I lost a few plants, maybe three out of the 20-some squash plants I started. I was able to harvest multiple C.Maxima N. Georgia Candy Roaster squash. Also my C.Pepo winter squashes were plentiful!

Squash is delicious. I hope my experience helps narrow down some strategies that may work great for you.

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My Action Plan for 2022

• Try more C.Moschata squash. Musquee de Provence is already a favorite
• In mid June, wrap foil about a foot or less at the base of the stems of all winter squash plants
• Mound soil over the stems as they grow
• By mid-June, have the traps set in the garden, about a foot off the ground
• Make sure I have BT and a new industrial syringe ready to go by end of June
• Do recon and do nightly egg check and destroy by crushing or into soapy water, dispose elsewhere
• Stagger planting of all squash with shorter growing seasons
• Find inner peace or anger management techniques as the SVB moth lays eggs all over my favorite squash
  
  Loving squash less is not an option.

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Thank you!

https://www.buymeacoffee.com/CElisabeth

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Additional Resources

https://extension.umn.edu/yard-and-garden-insects/squash-vine-borers

https://www.thomas.k-state.edu/lawnandgarden/docs/squashbugs.pdf

https://entnemdept.ufl.edu/creatures/veg/leaf/squash_vine_borer.htm

https://extension.unh.edu/resource/managing-squash-vine-borer-problems-new-hampshire-fact-sheet

A LATE NOTE: It is possible, and even common down south for a second generation of SVB moths to emerge in later summer. Well, guess what happened last year, here. Up north.

Yup. I noticed SVB moths in September, after not seeing any in August. The good news is that firstly, there weren’t that many. Secondly, they likely did not have time to eat enough to pupate over the winter, before frost hit and the plants died anyway. That was a first for me.

The End