Keeping watch for the squash vine borer.

squash vine borer

This morning I took a garden tour with a mission. I was on the lookout for signs of the squash vine borer on my zucchini plants. Control is very difficult, let alone organic control. What starts as a small problem the first year can become unmanageable over the next few years. This little guy can destroy your entire zucchini, squash, melon, cucumber crop and more. Vine borers are a moth that flies during the day. The only moth that flies during the day. Here’s where my confusion started. These guys look nothing like your typical moth. They are orange and black with clear wings. At first glance, you might think they are a bee or wasp. Truthfully, I have only ever seen one a couple of times. They are pretty sneaky and I think watchdog is pursuing a lost cause.

Squash vine borer damage

Vine borers lay their eggs on the plant near the base. When the eggs hatch, the worms bore into the plant. The signs of vine borer damage come on slowly. You might not notice you have a problem until it’s too late. The lower leaves will start to wilt and turn yellow. Crusty, dusty, white stuff collects around the base of the vine. If your zucchini or squash plants are large it might be slightly hidden under the leaves.

Cut the vine and remove the worm

There are three options I have tried that work and several that don’t. Cutting out the worms, covering the plants with tulle, and dusting with DE. In an effort to keep my garden organic, the first step I took when I discovered the problem was to cut out the worms. A sharp knife and quick fingers solved my problem. Slice the vine, pull the little guy out. More bugs and too many slices? No problem, just bury the vine and it will grow new roots. This was a really great solution for about three years.

Bury the vine so it can re-root

Then, one year, I cut open a vine and found 25-30 worms. I just couldn’t get them all. If this is your problem, I feel your pain. My little man didn’t get his chocolate zucchini birthday cake that year.

Cover plants with tulle

The next thing I tried, (remember I’m leaving out all the useless things I tried first) was to cover the plants with tulle. I use this technique often to keep away birds, rabbits, and insects in other areas of my garden. You can buy a whole bolt of tulle at the fabric store or Wal-Mart. It isn’t that expensive and I’m still using the one I bought three years ago. Tulle is that stuff wedding veils and tutus are made of. It comes in practically every color, but I just use white.

DE hurts bees and other helpful insects.

Covering the plants with tulle worked well for one growing season. But why won’t that always prevent the moth from reaching your plants? The moths can’t land on plants covered in tulle. However, vine borers hibernate in the dirt. The babies hatch under the tulle.

I decided it was time to bring out the big guns. DE or diatomaceous earth is an organic product I use sparingly. Without getting super technical, DE is basically crushed fossils/rocks. It has an incredible drying effect on an insect’s exoskeleton (and your skin). Wear gloves and cover up. If you don’t wear a mask, stand up wind when dusting. You should never inhale any product, organic or not.

Diatomaceous Earth for vine borer prevention

By dusting plants with DE, any eggs that have been laid on the vines won’t make it. Neither will the moths or bugs that crawl through it. Which leads me to a very important point. Do not use DE once your plants have flowered. This stuff isn’t selective. Our bee population is declining so, don’t use DE unnecessarily. Besides, if you keep your tulle on after the plants flower you shouldn’t have a problem. Here, in West Fargo, I haven’t had problems with moths after the zucchini plants flower. Further south, moths are active longer into the summer. Check your local extension if you have more questions about that.

Another solution, that I have yet to try, is growing Hubbard squash. Vine borer moths really like Hubbard squash better than any other plants. They will lay eggs there first.

There are a few options for squash vine borer control. Cutting out the worm, tulle, and DE. Dusting with DE and covering the plants with tulle until they flower has worked the best for me. This is a frustrating problem to have in your garden, so I hope these methods will offer a solution for you. I would love to hear if anyone else uses another organic method that has proven effective. Happy gardening!

-Nicole

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