Wildflower plantings near crop fields are a common tool for attracting pollinators, but a new study shows pesticide applications to crops are likely to drift as far as 100 feet into these wildflower zones, potentially harming the very pollinators they’re meant to attract. (Photo by Kirsten Strough, U.S. Department of Agriculture, public domain)

By Andrew Porterfield

Andrew Porterfield

Pesticides have been linked to population declines in hundreds of wild bee species in the United States, as well as to bumble bee activity in Europe. While efforts like integrated pest management have aimed to reduce pesticide use, pesticide applications have increased worldwide, threatening pollinator populations.

One part of a typical integrated pest management program is to reduce pesticide drift into non-targeted plants. These efforts include more targeted spray nozzles, adjustable spray pressure, reduced active ingredient volumes, slower tractor speed, and field buffer zones. Buffer zones separate crop fields from areas planted with wildflowers that support pollinators and other beneficial insects. But do they work? And how wide a buffer zone will prevent drifted pesticides from entering such a non-crop field?

A new study by researchers at the USDA Agricultural Research Service and Cornell and Michigan State universities found no significant reduction in pesticide active ingredients in buffer zones that extended between zero and 105 feet (32 meters) from the edge of a sprayed crop field. Their study, published in June in Environmental Entomology, recommends other types of drift reduction measures instead, such as windbreaks and more precise application methods.

Looking at fields of highbush blueberry plants in Michigan, the researchers invented a method to measure pesticide deposition using silicone wristbands. The bands were attached to 48-inch-high fence posts and spaced at regular intervals (zero, two, four, eight, 16, 24 and 32 meters) from a blueberry field. They tested for exposure at 15 blueberry farms. However, due to funding restrictions, the researchers could only test one band per distance, per site. The researchers were still able to analyze 104 samples.

Looking at fields of highbush blueberry plants in Michigan, researchers invented a method to measure pesticide deposition using silicone wristbands. The bands were attached to 48-inch-high fence posts (close-up in inset) and spaced at regular intervals from the edge of a blueberry field, as shown here. (Image originally published supplemental to Graham et al 2025, Environmental Entomology)

The researchers analyzed the samples for pesticides using ultrahigh performance liquid chromatography and mass spectrometry. They found 42 pesticides across all samples, primarily herbicides and fungicides. The team did detect insecticides as well, including carbaryl, phosmet, and methoxyfenozide.

“There was no decline in the average number of active ingredients across all distances tested,” the researchers write. While the study did record a significant decline in pesticide concentration as distance from the crop field increased, this was largely due to reduced concentrations of fungicides between 24 and 32 meters away from the crop. “Insecticides and herbicides had no significant decline in concentration across the tested distances,” they write.

This finding also is significant, because the wildflower fields planted to support pollinators at blueberry farms in the study were about 1.2 acres each and had a typical width of just 16 to 20 meters. This means that the farthest edge of wildflower plantings were just 26 meters from blueberries. Thus, “the entire planting is likely to be within the area where we found no significant reduction in pesticide concentrations with distance from the field edge,” they write.

Of the pesticides found, the insecticide phosmet was of particular concern, because it is a major factor behind bee declines during fruit ripening. The median lethal dose (i.e., sufficient to kill half of a tested population) of phosmet for honey bees is 0.22 micrograms per bee. Phosmet concentrations, which did not vary according to distance, were detected at 55.8 parts per billion (ppb) at the blueberry row and 44.6 ppb at 24 meters.

Other mitigation measures are available to reduce drift, “but their adoption is low in most farms,” the researchers note. These other options include windbreaks, spray nozzle technology improvements, sprayer calibration, and drift control adjuvants included in the pesticide formulation. “Further research is needed to test the effectiveness of these drift reduction methods, as well as understanding how far drift goes at concentrations that are relevant for beneficial insect health,” they write.

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He is based in Camarillo, California. Connect with him via LinkedIn or via email at [email protected].