Squash vine borers are one of the most insidious insect pests in the garden. They attack many vine crops in the vegetable garden especially pumpkins, winter squash, summer squash such as zucchini and yellow crook neck, and gourds. Sometimes they will infest muskmelons, watermelons and cucumbers. I’ve had them many times in squash and only once in cucumbers.
Although the adult stage of the borer is a moth, it doesn’t look like or act like a moth. Unlike most moths it flies during the day. And instead of fluttering around like a moth, it flies quickly, like a wasp.
The female adult lays its eggs on the base of the main vine, the eggs hatch and the baby borer eats its way into the vine and keeps feeding and growing for about four weeks. It’s very possible that our squash and pumpkin vines have borers in them right now even though they are not exhibiting any visible symptoms.
At first it’s easy to confuse borer symptoms with drought. The plants wilt on hot, sunny days then recover overnight. If left alone, eventually the plants suddenly and completely collapse. The most startling symptom of a squash borer infestation is seeing healthy vigorous vines one day then seemingly the next day they are collapsed, wilted and dying.
You can help your vines minimize borer damage by taking advantage of vine growth habits. You’ve probably noticed that squash and other vines sometimes root themselves further away from the base of the plant. Those roots are actually functional and contribute to the vine’s growth.
By encouraging rooting along different places along the vine, you can minimize the damage the borers do since the vine can get still get water and nutrients from the soil because of the extended root system. If the plant had to depend only on the roots at the base, no water would be able to reach those parts of the vine past the area damaged by the borer.
Rooting takes place at the nodes of the vine; those swollen spots on the vine from where the leaves grow. To encourage rooting, cover several nodes with a shovelful of garden soil. The secondary roots that form will support the plant even if the primary vine is damaged by borers.