Instead of Using Pesticides, Farmers Can Plant More Flowers

Planting flowers is no vanity. Not only does having a variety of blooms dotting the edges and uncultivated parts of a farm provide forage for bees and other pollinators, but it can reduce the amount of pesticides used on crops.

That’s the major finding of a study published last week in the journal Agriculture, Ecosystems, and the Environment. Researchers from the University of California Division of Agriculture and Natural Resources and UC Berkeley looked at how planting hedgerows of native California plants alongside farmland in Yolo County increased the population of predatory insects that eat crop pests such as aphids. The two-year study found that more parasitic wasps were in the hedgerows than in those fields where the borders were left to the weeds, which were studied as a control. While there were the same amount of arthropod predators—ladybugs and spiders and such—in the weedy edges, there was more diversity in and around the fields with planted edges.

“We found that small-scale restoration in intensive agricultural landscapes can enhance some natural enemies, both in edges and in adjacent crops, while decreasing pests in edges and adjacent crops,” the authors wrote. The reduction of crop pests such as aphids wrought by the predatory insects attracted by the hedgerows reached 200 meters into the fields, which, considering that the plantings observed in the study were approximately 400 meters by 400 meters, is dead center. Simply changing what grows along the edge of a field—which can also help control dust, erosion, and other issues—helped provide pest control for the entire crop.

The research was conducted in 2009 and 2010, before the current drought settled in. But many of the species used in the hedgerows studied—including ceanothus, California buckwheat, and Mexican elderberry—are highly drought-tolerant and can likely survive on rainfall and a small amount of summer irrigation after becoming established. While buying native shrubs costs more—a total of $4 a linear foot—than giving field edges over to weeds, the investment is a good one, according to a press release. Thanks to decreased pesticide use, a farmer can break even in 15 years and even more quickly if the hedgerows, which also provide pollinator habitat, help to reduce the amount of money spent on renting honeybee hives. Federal programs, including the Natural Resources Conservation Services, help farmers cover costs.

Materials on hedgerows from local cooperative extension programs and conservation groups always mention rodents, which like the extra cover, and there has been widespread concern that having anything alongside fields other than bare dirt could present a public health threat by allowing wildlife to transmit bacteria such as E. coli to crops. But a recent study found that clearing field edges had no food-safety benefit and destroyed habitat for beneficial insects.

Outside California, the introduction of native wildlife habitat in the midst of crop plantings has been found to help reduce runoff and curb erosion on corn belt farms.