Squashing the vine borer
Chances are that if you have a garden, you have at least one squash plant producing flowers and fruit right now. At the Armstrong garden, we have zucchini, summer squash, acorn, butternut, hubbard, patty pan, giant pumpkin, mini-pumpkin, cukes, and melons, plus a few heirloom varieties that came to me without packaging. That's a lot of squash!
As an experienced organic gardener, I knew to expect the inevitable infestation of their vines by an insect known as the Squash vine borer. The vine borer has probably wreaked havoc in your own garden. Have you noticed a powdery orange-gold substance near holes at the base of your squash plants, along with wilting leaves? That is "frass," and it marks the entry hole for the borer. This complicated insect hatches from eggs that were laid at the base of young plants by a rather pretty looking moth that more resembles a beetle. The eggs hatch into grubs, which crawl within the vines and feed there, sucking the life from your plants. They will eventually metamorphose into the winged adult, which will then lay more eggs, either this year or next. Unless, of course, you stop them.
I found a number of tips to help you protect your plants from the vine borer, which I list below, but I find this method works best: wherever you see "frass," slit the vine along its length about an inch above and below the entry hole. Old-timers will tell you to then insert a crochet hook into the vine to pull the grub out. I use a piece of wire coat hanger with a bent tip (needle-nosed pliers work well to put a small curve at the end of your hanger). I generally find one or two grubs per vine. Sometimes there are multiple entry sites, and every one of them will have a grub or two hiding inside. To help the plant recover from this "surgery," I pack some nice rich dirt over the wound. The plants rebound nicely, continuing to yield tasty squash until the mildew takes over. There are few organic remedies for mildew, but I'll have to leave that for another blog post.
Here is what you can do to protect squash plants from the vine borer:
Discard plants that cannot be saved: Don't put them in your compost or leave them lying around, or the larvae may grow into an adult and re-infect your squash next year.
Use a floating row cover, or tin foil, or pantyhose. Covering plants will prevent the adult moth from laying eggs where you don't want them. Keep in mind that a row cover will also prevent bees, or any other pollinating insect, from reaching your plants. You might try covering just the vine with foil or panty hose.
Set traps to know when they have emerged. You can tell when the squash vine borers are emerging by looking for the adults, or by setting a yellow bowl full of water in your garden. The moths are attracted to the yellow, and get trapped in the water. When you find one in your trap, you know it is time to take action against them. It is also a sign to start looking for eggs on the stems.
Plant vine crops that are usually not attacked by squash vine borers. Thinner vines make unsatisfactory homes for vine borers. Try butternut squash, cucumbers, melons, and watermelons.
Hand pick and destroy eggs. You won't get every egg though, I'll bet
A second planting of summer squash made in early July will mature after adult borers have finished laying eggs. Areas with longer growing seasons might have two rounds of vine borers in a single season, but in New York this is a good method.
Till the soil in fall. Larvae that are brought close to the surface should freeze in winter. Make sure to kill any grubs that you find while tilling.