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Squash Vine Borer Pest Profile

About 3 weeks ago, while I was scouting my vegetable garden, I saw a precursor of the inevitable squash vine borer invasion. A strange, black and orange, wasp-like insect was relentlessly probing in and out of my squash and zucchini rows...

"Oh no! Is that what I think it is?

Already!? I haven't even picked my first squash yet!"

It was an adult squash vine borer. The nerve of this moth to dress up like a wasp and shamelessly lay her eggs all over my squash stems and in BROAD DAYLIGHT nonetheless! Fast-forward three weeks and now my squash plants are really starting to suffer.

(Small brown squash vine borer eggs on stems)

Why is the squash vine borer such a problem?

Approximately one week after they are laid, the eggs hatch and the resulting borers, which are a type of caterpillar, drill into stems to feed. The larvae feed through the center of the stems, blocking the flow of water to the rest of the plant. The developing squash vine borer larvae tunnel and eat their way through the larger stems, causing plants to wilt and eventually die. The larvae feed for four to six weeks, then exit the stems and burrow about one to two inches into the soil to pupate.

(Squash vine borer damage on stems)

(squash vine borer larva)
(squash leaves are turning yellow due to squash vine borer damage, next stage will be wilting)

How Can We Manage this Pest?

Control is difficult, but prevention is key. If this insect is detected early, it can be carefully cut out of the stem with a sharp knife. Soil should then be mounded over the plant wound to encourage rooting. A trap crop can be utilized to entice the borers away from your summer squash. Trap crops are sacrificial plants that draw damaging insects away from the desirable crop. University research suggests that if you plant Blue Hubbard Squash two weeks ahead of your favorite squash, it will lure the moths away from your table bound veggies. By planting the Blue Hubbard squash first, it ensures that the trap crop is larger and more desirable to the pests. When squash vine borers get established on a trap crop it makes chemical control an easier choice because you don't intend to eat any of the trap crop that is being treated with insecticide.

Squash vine borer infested plants should be disposed of by bagging and completely removing them from the property or by burning. Otherwise, the larvae that remain in the plant can still pupate in a trash pile and will likely mature into another generation of pests during your next squash growing season.

Another alternative is choosing to grow a squash variety that is less susceptible to borer feeding damage. Zucchini and yellow squash are a borers favorite, however, the hard squashes and winter squashes seem to fare better against this enemy. There is an heirloom variety of squash called Zucchino Rampicante that is rumored to be impervious to this pest because it's vines are so thick. This zucchini variety produces long slender 15-inch fruit that has a flat bulb at the bottom. It is a unique vegetable to behold and may be worth a try if you are ready to give up growing squash because of the borers.

(Zucchino Rampicante)

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Happy Growing!


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