Squash Vine Borer

Lynne Forbragd, UM Extension Master Gardener in Anoka County, June 10, 2015

Growing zucchini can be one of the easiest vegetables to grow if you have the right growing conditions. You can get so much produce that neighbors avoid making eye contact because they don’t want to be given any more zucchinis. Don’t forget about the zucchini that gets hidden under the leaves. Virtually overnight a zucchini can grow to a foot long.

Larva of squash vine borer

Larva of squash vine borer

But what if you don’t get the production from your zucchinis that you’ve been hoping for? If the plants have been healthy and they start to look like they are wilting, this is a sign that it is being infected by the squash vine borer. The squash vine borer can inhibit getting a high yield from your vining plants. The plants that are more susceptible to it are zucchini, summer, Hubbard, Acorn, Buttercup squashes and pumpkins. Vining plants less likely to be affected are Butternut squash, melons and cucumber. There are natural and chemical methods that can prevent getting the squash vine borer.

In late June to early July, daily inspection is required to see the signs before wilting occurs. The squash vine borer is a black and orange moth that flies like a bee and is about 1”-1 1/2” long. The moths are attracted to the blossoms and will lay its eggs at the base of the vine which look like reddish brown specs. When you see these, gently brush them off and drop them onto a paper towel. If you see little holes and a saw dust like substance at the base of the plant; the larvae has hatched and eaten its way into the vine and will start the destruction of the plant. At this point, take a needle and pierce the vine at ½” intervals to kill the larvae or a fine blade and make a slit near the entrance point. Mound up moist soil around the plant to help the plant recover. This process can be labor intensive depending on how many plants have been infected. If this method is unsuccessful, pull and toss the plant to minimize infestations the following year.

Another successful method is to time your planting. The moth lays its eggs from late June to early July so by waiting to plant in early July, you will miss the egg laying stage. This works for vining plants that have a shorter length of time to harvest.

Row covers is another method. Cover the plants late June to early July ensuring that the covers are tight to the ground to prevent the moth from entering the protected area. It is necessary to rotate your crops as the eggs come from out of the soil from the previous year.

If these other methods have not worked, insecticides can be applied. Spray at the base of the plant when the moth is active and reapply two times every 7-10 days. Effective insecticides are carbaryl, permethrin, bifenthrin and esfenvalerate. Always read the label when using insecticides to ensure proper applications and to minimize residual effects in the soil.

For more information, see: http://www.vegedge.umn.edu/pest-profiles/pests/squash-vine-borer .