The potato beetles are coming, and we’re ready for them.
Every garden has its nemesis, and ours is the Colorado striped potato beetle, a sly creature that tends to acquire resistance to whatever pesticides are used against it. According to one theory, the beetle’s co-evolution with toxin-containing host foods in the nightshade family - potatoes, tomatoes, eggplants, peppers - has made it able to adjust to toxins in general.
At our place, we’ve tried to avoid the pesticide issue altogether by evolving our own campaign against the pest with a bag of nontoxic tricks. We’ve found that in very wet summers, our potatoes are especially vigorous and able to ward off beetle attacks, so we mulch the crop heavily with decomposing hay to maintain moisture levels. The mulch also keeps the sun from warming up the soil too much, which would stress the plants and make them more susceptible to the beetles.
We encourage birds and pest-eating insects by keeping our farm poison-free. Sometimes we put a barrier of floating row cover over the potato crop at planting time. We rotate the potatoes to a new spot each year to make it harder for overwintering beetles to find. And we pick off any egg masses, larvae and adult beetles that appear, as these creatures are voracious and can entirely defoliate the plants. If we have postponed this depredation long enough by hand-picking, we’ll find a decent crop of potatoes waiting for us under the soil.
This year, we’re also trying a trap crop. It’s a time-honored garden practice by which you deliberately plant something as a decoy to lure a pest away. It could be a completely different plant, such as a row of radishes to distract flea beetles from the arugula. Or it could be the same crop you’re protecting but at a different time or place. For instance, we’ve sprouted some of our seed potatoes extra early and set them ahead of the main crop in the section of the garden where they grew last year, where the beetles are sure to find them. Potato beetles overwinter in the soil as pupae near the place where they have been feeding, then emerge in spring as adult insects, ready to walk or fly to the nearest nightshade-clan feast. When they do, we will start destroying any we find, before they have a chance to move on and discover where the main crop is growing.
This is important, of course. There’s no point in trying the trap crop maneuver unless you make every effort to eradicate what you attract. Look under the leaves for orange egg masses and rub them off with your fingers. Knock the round, striped adults into a quart yogurt container full of soapsuds before they can fly away. Drown the fat, bloated pink larvae, too, or squish them with your fingers. Disgusting? Yes. Tedious? Yes. But easier to do it with this small crop than with your larger one. At times it’s best to cut off the most affected leaves and plunge them into a bucket of water, a fate the pests will not survive.
Another trap crop you can try is eggplant, which potato beetles love most of all. And because the flea beetles do, too, your arugula will thank you as well.
Damrosch is the author of “The Four Season Farm Gardener’s Cookbook”; her website is www.fourseasonfarm.com.