How to Grow: Controlling Squash Vine Borer

Learn about the best organics controls for the squash vine borer insect.

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We’ve all seen this happen. Beautiful summer squash, pumpkin or winter squash plants are thriving in July, only to start wilting during the day, even if the soil is wet. After closer inspection you see holes in the plant base. Yes, it’s the squash vine borer. This destructive moth lays eggs in July at the base of these plants. The larvae burrows into the stem causing it to wilt. Severe infestations can kill your plant.


But all is not lost. If you catch the infestation early, you can physically remove the larvae and maybe save the plant. It’s time to play surgeon. With a sharp knife or razor slit the stem at the hole going away from the base of the plant. You’ll soon find the fat, white larvae. Remove it and feed it to your chickens. They’ll love it! Cover the slit with soil and water well. Hopefully the vine will reroot and survive. You can also inject B.t. organic pesticide into the stem with a syringe where you think the larvae is tunneling. The larvae will eat the B.t. and die without harming the plant or us.

Prevention, though, is probably the best cure. Plant resistant squashes, such as butternut. Cover young plants with a floating row cover until flowering. After flowering cover just the base of the plant with row cover to make a barrier to prevent egg laying. Delay planting zucchini and summer squash until early July to avoid the egg laying stage. Set out a small yellow pail with water in June to trap the day flying, moth. They’re attracted to the yellow color and drown in the water. Remove infested plants and rotate crops each year.

From the Vermont Garden Journal on Vermont Public Radio.