Dear Carol: Is there a way to eliminate the possibility of squash vine borers next year that is environmentally safe? The garden looks gorgeous to begin with, and pumpkins, winter squash and zucchini get a great start. But the damage is done by the borers before I find them. I used to plant tomatoes in coffee cans--would something like that help? -- N.S., via email.
Dear N.S.: Good for thinking ahead. Many of next year's garden problems can be minimized by taking steps now.
The squash vine borer is the caterpillar of a clear wing moth. This insect is unmothlike, both because of the clear wings and because it flies in the daytime. Most moths are active at night.
In the northeastern United States, there is a single generation a year. That is key to managing them. When the caterpillars have finished destroying squash plants and are full grown, they burrow into the soil and pupate. That's where they are now.
The pupae remain in the soil all winter and spring. In late June, the adults emerge and mate. The females then lay eggs singly on the stems of squash plants. The moths prefer winter squash, summer squash and pumpkins, but can also attack watermelons, cucumbers and others in the family.
The eggs hatch and start to feed inside the stems. Often nobody notices until August, when the vine suddenly wilts and dies. Upon examination, the stems are chewed up and filled with greenish or orangish frass -- caterpillar excrement. The caterpillar is large and white, with a brown head.
Plan for better yields next year by cleaning up all squash plant debris after the final harvest. You can try turning over the soil to expose the pupae, in the hope that some bird or mammal will eat them. Rotate your crops. Plant the squash somewhere else next year, or take a break from squash altogether for a couple of years. That is what I did when the population got very high.
Plant resistant varieties. Waltham butternut winter squash is resistant because the plants have solid stems. Plant summer squash late, after June 30, when the moths have emerged and mated. If there aren't any zucchini plants yet, too bad for the moths.
Protect young plants with non-woven row covers. Reemay is one brand name. Be sure the cover is secured all around the edges. The covers must be removed for pollination once female flowers are being produced, but the moths are gone by then.
Surround WP (wettable powder) is a kaolin based insect repellent that is approved for organic growers. Kaolin is a type of white clay. Bugs don't like it on their bodies. Kaolin can be used to repel many garden pests, but has to be reapplied frequently, following label directions, because it washes off. It can be used until the day of harvest if needed.
Think about the pest and disease problems this season and learn about them. It's too late once the damage has occurred.