It’s like something out a horror movie…thousands of gray and brown, six-legged creatures pour out from under a leaf ready to devour. Meanwhile, deep inside the stem a fat, greasy sluggish creature eats the victim from the inside out. But this is no film, this is your garden. And these monsters are eating your squash.
Earlier this month my squash plants were kicking out dozens of gorgeous zukes, patty-pans and yellow summer squash. Also a gorgeous albeit misplaced pumpkin plant was crawling over my front lawn, covered in blossoms and little baby pumpkins. Meanwhile, a spaggetti-squash plant was climbing over my white picket fence and dropping large fruits while a bird-bottle squash wrapped itself around the garden and over my pole beans, dropping little ‘bottles’ along the way. Now the zucchini plants are turning brown, the tiny zukes are shriveling, the flowers dropping off. The pumpkin leaves are yellowed and the pumpkins themselves, which were on their way to jack-o-lantern size, are stunted and already turning orange. The spagetti-squash vines are dried and brown and falling down and the bird-bottle is starting to wither. Another scene from THE GARDEN OF HORROR? Sort of.
While I, their protector was otherwise engaged–playing with friends, entering the garden only to harvest and show off–the most hideous monsters were munching on my squash: the dreaded squash borer (caterpillar/moth) and the ubiquitous and rapidly-multiplying squash bug (‘beetle’).
So now you have identified the enemy–but how do you fight them?
The problem begins in late Spring, when a moth lays its eggs at the base of your squash plants. Each female lays about 200 eggs, but one at a time rather than in clusters, making the tiny eggs almost impossible to spot. They hatch in a week or two, and the evil little caterpillars that emerge quickly tunnel into the hollow plant stems where they feed, hidden from view, for a month or so and then drop down into the soil to pupate. In our area, they emerge as adults the following Spring.
One way to avoid the adult moth—which looks like a little red-bellied wasp—is to cover your squash plants withfloating row covers which allow water, light and air through, but prevent bugs of all kinds—including bees, which is a problem. If you go this route, make sure you plant where squash didn’t grow the previous year (or the moth may emerge inside the row covers—eeek!) and either grow self-pollinating varieties or lift the covers and pollinate the flowers yourself with a little paintbrush. In our area, you can remove the covers entirely by the Fourth of July; all the egg-laying action will be over.
Another prevention is to grow your squash out in the open and use vigilance to get the eggs. You may not be able to see them, but a weekly spray of the vine with insecticidal soap will smother them nonetheless. If you are really vigilant you can wipe the stems every five days vigorously with a damp cloth (or one wetted with the insecticidal soap) and wipe away the eggs.
Once the season is underway, carefully inspect each vine once a week; don’t wait for wilting! If you see a hole near the soil line and that distinctive greenish frass (bug poop) that the borers push back out of their comfy new home, slit the vine with a razor blade and find the caterpillar inside. Do with it what you will, o’ avenging angel. Then cover the damaged vine with compost-rich soil.
Or inject the attacked vine with beneficial nematodes; these microscopic garden helpers love to prey on tasty caterpillars, and the moist inside of the vine will protect the nematodes as they go a’ hunting.
If none of these work, in our area you can replant with new squash plants any time after mid-July; it will be too late for the new borers to do their evil work.