glinda30
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How to control Squash Vine Borers

I have tried unsuccessfully to grow zucchini and squash for 3 years. The plants do beautifully until the SVB's show up. I have read about slitting the vine and pulling out the bug, but there is still a good possibility of losing the plant anyway. I would like to try thuricide, but not sure when and how to apply it. Can I spray the soil around the plant to prevent them from coming near the plants? If I spray the whole plant will it prevent them from chewing into the vine. I would like to get rid of them before they have the opportunity to make their way into the vine. I am on a mission and determined to grow zucchini. Any help will be greatly appreciated. Thanks

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rainbowgardener
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Sorry, but:

The available forms of Bacillus thuringiensis (Bt) formulations are not effective against this pest; it is difficult to spray the internal parts of the stems where the larvae are eating
https://www.vegedge.umn.edu/vegpest/CUCS/vinebor.htm

They do say if you spot any signs of the larvae in the stem you can inject the thuricide into the stem, like with a syringe. I haven't tried it, so can't really comment.

I haven't really solved this problem myself yet. It helps to keep the plant under row cover as long as you can and to cover the stem with dirt, foil wrap or other barriers to the larvae entering.

But so far all I have been able to do is delay when they kill my zukes, not avoid it.

It does help if you grow one zuke plant in the middle of a bunch of flowers and herbs, makes it harder for the insects to find it.
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cyanidecotdpnuts
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Have you thought about trying beneficial nematodes? Less harmful than insecticides and probably alot cheaper too.

Although it doesn't say Vine Borers specifically, it DOES say it attacks over 200 species of soil pest including Vine Beetles and Borers.
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rainbowgardener
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Thuricide isn't really an insecticide. It is the commercial name for Bacillus thuringiensis, a bacterium that infects and kills only certain kinds of insects. It is otherwise totally harmless in the environment. It only works against insects that ingest it by eating leaves, mainly leaf eating larvae like hornworms, gypsy moth larvae, etc. This does include the larvae of some butterflies, so you need to be careful with it if you want butterflies in your garden.
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glinda30
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Thanks folks for all the input. Sounds like I have to wait until the borers are already in the the vines before anything can be done. I live near Clemson Extension so I had asked them about it and they recommended Bacillus thuringiensis (Thuricide). I was just hoping to spray it and take care of the problem before the borers had the chance to make it's way into the vine. I tried last year to remove the borers by slitting the vine, removing them and then covering the vine in dirt but it didn't work. I lost the plant anyway.

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rainbowgardener
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Another preventative I have seen recommended, but have not tried, is Surround, kaolin clay. It is sprayed on and I guess hardens into clay. It is another form of physical barrier to keep the larvae from being able to penetrate the stems.
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Kisal
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I don't grow squash, as I don't care for it, but I have read that wrapping the lower 4 to 6 inches of the main stem with aluminum foil will keep the borers out. Again, I haven't tried it, because it's a veggie I don't grow.

The wrap would have to be started as soon as the plant was large enough so the stem wouldn't break while being wrapped. More foil would have to be added as the plant grew.

Just something I read. Don't know if it would actually work, though.
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rainbowgardener
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I have tried it. You have to wrap the stem starting from a little below ground level and you have to keep wrapping new stem anywhere it is close to the ground. It's part of what I was referring to when I said that I was able to delay the death by SVB, long enough that I was actually able to eat a few zukes from my garden. But the foil tends to loosen up over time unless you are really vigilant, and I think I wasn't careful enough about keeping everything wrapped. Anyway eventually they found a way in....

The worst pest in my garden! I haven't tried the kaolin clay yet, maybe this year.
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nedwina
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If it's just zukes you're after, try growing Tatume. It's a tough, soild vined squash that tastes like zuke when picked early/small. Sandhill has it. It's a very suitable substitute. Trombocino ain't bad either, and the SVB don't seem to be interested in that either.

SVB are moth larva. So they fly in, lay the egg & take off. The worm hatches, drills in and munches the interior of the vine until it reaches maturity. Then it drills out, drops to the soil and wriggles in to pupate. They overwinter in their hard shelled pupas until the following late spring/early summer. Beneficial nematodes will help if you apply where last year's patch was. But that'll only kill off your locals, not the ones next door...

Do some searches on Melittia Cucurbitae.

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