This June 2005 essay was written by Amanda Cather, Farm Manager at Waltham Fields Community Farm. In it, she talks to CSA shareholders about organic pest management.
Not a big fan of pesticides, even organic pesticides, A. Cather, 2005
It will come as no surprise to any of you, I’m sure, when I tell you that this has been a cool, wet spring. Our crops are growing slowly (but many early season weeds are not!). Farmers, despite our reputation as conservatives, are actually some of the greatest risk-takers around; we tend to push the envelope from year to year on getting things in the ground early whenever we can. The nor’easter that tore through therefore, put a crimp in the planting of some of our warm-weather crops, including wiping out our first cucumber planting and many of our pumpkins. Waltham Butternut squash, a variety developed at the field station, was one of the major casualties, with 100% losses in the field. While we were re-planting the pumpkins and winter squash on the steamy Sunday of Memorial Day weekend with some extra plants that we were fortunate enough to have in the cold frame, Marian Friedman and Chrissy Kellogg noticed a pretty yellow-and-black striped beetle sitting happily on one of the leaves of the few remaining plants. Then they noticed another one . . . and another . . . and five more . . . and twenty more.
The striped cucumber beetles, woken from their winter slumbers, had arrived in the field. Striped cucumber beetles overwinter in the dense vegetation that borders our fields. Members of the first generation emerge when the weather moderates in the spring (conveniently, right around the time that we risk-taking farmers plant our first cucurbits), mate, and lay their eggs in moist soil at the base of the plants in the cucurbit family—pumpkins, winter and summer squash, watermelons, cantaloupes, and cucumbers. When the larvae hatch, they munch on the roots of these plants until they become adults, emerge from the soil, eat the leaves of the plants, often finding a younger planting in the field to decimate, lay more eggs, and begin the cycle again. Of course, one beautiful yellow-and-black beetle in the first generation means many, many larvae and beetles in succeeding generations.
This by itself would be a challenge, but the first generation of cucumber beetles also carry a disease called bacterial wilt, a tricky sickness which causes cucumbers and cantaloupes to wilt, collapse and die—but not until they appear just about ready to produce. Because of this, although as organic farmers we tolerate and even expect a certain level of pests in our crops, the level of this first generation of cucumber beetles that we can take is extremely low, less than one beetle per plant. Even though we rotate our crops, and even though last year was a fairly mild season as cucumber beetles go, the numbers that Marian and Chrissy were seeing in our already-stressed plants was more like 10-20 per plant.
As many of you know, I’m not a big fan of pesticides, even organic pesticides, and certainly not as a first resort—and there are many other techniques that we can use to “hide” our cucurbit family crops from the beetles, like reemay, the white floating row cover that we use for many other pests (including woodchucks) and a non-toxic spray-on white clay coating that disguises the plants and confuses the beetles. But these beetles had emerged immediately following the storm, we hadn’t had a chance to spray the clay on the plants, and all our reemay is currently protecting other crops—and the beetles had already found the squash and pumpkins. Striped cucumber beetles, particularly in the huge first-generation numbers that we were seeing in the field, are nothing to be trifled with. I knew that the combination of beetles and nor’easter would mean no pumpkins if I didn’t do something very quickly. So I put on a head-to- toe rainsuit, shouldered the backpack sprayer, mixed up an emulsion of fish oil and Pyganic, an organic pyrethrin that kills beetles on contact, and spent the rest of that day and some of the next spraying cucumber beetles. The night between the two sprays, I was up for two hours alternating between picturing cucumber beetles swarming over the pumpkin plants (unlikely at 2:00 in the morning), regretting the fact that Pyganic is toxic to beneficial insects as well as harmful ones, and being grateful that the pumpkin and winter squash plants had not yet flowered, meaning that very few honey bees, if any, were in the path of the backpack sprayer.
Small worries in the context of world events, to be sure, and at least we aren’t spraying toxic synthetic chemicals on our food plants—Pyganic breaks down very quickly in the environment, and is even considered safe to spray on the day of harvest (you should know, however, that we do not spray any pesticide on the day of harvest, ever). When I returned on Tuesday morning, the number of beetles on the plants had decreased dramatically, but it felt like a mixed blessing nonetheless. Meanwhile, the potato beetles have emerged at the same time as the slow-growing potatoes and the cold-stressed tomatoes, the woodchucks are eating huge quantities of lettuce and broccoli, and our weeds are outgrowing the carrots. But the double rainbow over the farm on Saturday night was one of the most beautiful I’ve ever seen, and the combination of blue skies and thunderheads all weekend long was enough to lift my spirits above the mundane. I slept well on Monday night. Such is the life of the organic farmer.