The Q&A Archives: squash plant malady

Question: For the last several years I haven't been successful with raising summer squash (zucchini and yellow straightnecks). I get very nice plants, they begin to bloom, and I may get one harvest, but then the stalks droop, they ooze at various places near the ground, and then they quickly die. I remember finding a potential cause in one of my books and was disappointed because no treatment was given.

Answer: What you describe sounds just like damage from squash vine borers. Just as squash is beginning to flower in your area, the adult moth lays eggs on the stems, usually within six inches of the ground. The eggs hatch and the larvae tunnel into the stems to feed for four weeks, which eventually causes the plants to wilt and die. There are two generations of moth/larvae a year and they overlap, which makes this a bigger problem throughout the summer. Prevent the moth from laying eggs by wrapping the stem with a barrier such as aluminum foil or covering the whole plant with a floating row cover until blossom time. If you use row covers, keep the plants well watered. Squash plants tend to dry out quickly under them. If the larvae get inside the stems and you see the sawdustlike frass begin to ooze out, inject Bt (Bacillus thuringiensis var.kurstaki) into the stems with a garden syringe about 1/2 inch above the soil line every two weeks, starting after first flowering. If you miss some of the borers, slit the stem, remove the larvae and replant the slit stem. In fall, remove and destroy the squash plant debris where the larvae overwinter. Be sure to rotate your crops so any overwintering pests won't have a ready meal when they emerge from the ground.

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