Wilting Zucchini

Over the summer so far I've lost a couple zucchini plants to pest attacks. Not knowing at first what was going on I did some searching for other gardeners that might have this problem.

Apparently, there are 2 possible causes for wilting zucchini (and other squash related plants). One is the squash vine borer, Melittia cucurbitae, and the other is simply known as the squash bug, Anasa tristis. Both will cause wilting and eventual death of the plant.

Initially, the plants look like they're seriously lacking water. Your first thought might be to water your garden extra well. I had even tried putting up a sun shade over a few of my zucchini plants - an old door suspended on saw horses. Adding some shade for the plants in the 99+ degree heat did help a little at first. But, when the temperatures would drop at night the plants wouldn't rebound, even with a lot of watering.

Another sure sign you have a sick plant(s) is that there are other, healthy plants around it. Here you can see my wilting zucchini right next to healthy, vigorous plants. Something is definitely wrong:

After seeing that the stems were rotting I decided to just pull them out. Away from the garden I dissected them a little more and found the offending bug, a grub of the squash vine borer:

I skewered the grub and put the whole plant into the trash can. I generally like to compost all the left over vegetation from the garden, but I didn't want any left over eggs to get back into the garden. Sadly, I decided to landfill this plant material.

The Offending Insects

The squash vine borer spends its adult life as a moth. Image from U. of MN Extension.

After hatching the grub chews its way into the stem near the ground and burrows into the plant.

The adult squash bug, Anasa tristis. Image from U. of Minnesota. (Click image for closeup.)

Squash bugs in various stages of development. (Click image for closeup.)

The Solution

If you can catch and treat your zucchini quick enough you might be able to save it. Usually, by the time most people notice the plant is wilting it's too far gone. The treatment for squash vine borer it to kill the grub, usually by carefully splitting the stem open lengthwise with a knife, and killing the insect. Dirt can then be mounded up around the stem to encourage new root growth. I did not try this myself as my plants were too far gone. But, next summer I'll definitely keep a closer eye on things and jump into action sooner.

As for squash bugs the U. of Minnesota advises to hand pick the insects off as early as possible. Have a jar of slightly soapy water next to you to plunk them into. Boards can also be placed on the ground next to the plants. The bugs will shelter under the boards at night. Pick up the boards in the early morning and squash them. Then in the Fall make sure to remove all vegetation from the garden so they don't have a place to overwinter under.

If you're ok with using chemicals then Sevin might be an answer for you. Please do thorough research before applying poisons to the vegetables you and your family are going to eat. Personally, I'd rather forgo eating zucchini for a year than have any pesticide in my garden. If you're feeding these veggies to kids I would definitely not use any pesticide or herbicide in your garden.