A recent study conducted by researchers at the University of Guelph in Ontario, Canada, that found organic pesticides may have a higher environmental impact than conventional pesticides because they kill predator insects, may not tell the whole story, according to an organic industry professional.
The study, published in PLoS ONE journal on Tuesday, involved testing six pesticides and comparing their environmental impact and effectiveness in killing soybean aphids— the worst pest affecting soybean crops in the North America, according to the research. Environmental science professor Rebecca Hallett and Ph.D. candidate Christine Bahlai looked at four synthetic pesticides: two conventional products commonly used by soybean farmers and two new, reduced-risk pesticides. They also examined a mineral oil–based organic pesticide and a product containing a fungus that infects and kills insects.
“Compared to the synthetic pesticides, the mineral oil–based and fungal products were less effective, as they also killed ladybugs and flower bugs, which are important regulators of aphid population and growth,” Hallett said in a release. “These predator insects reduce environmental impact because they naturally protect the crop, reducing the amount of pesticides that are needed.”
Pam Marrone, on behalf of the Organic Farming Research Foundatin and CEO of Marrone Bio Innovations based in Davis, Calif., which specializes in biopesticide, found errors in the study design. First, mineral oil is not widely used for insects on this crop, nor is fungus. “This is very misleading,” she said. “If they were going to do a legitimate study they should pick a crop where biopesticides are widely used—a fruit or vegetable crop, for example—and and analyze more widely used biopesticides.”
The researchers determined the impact of the pesticides on such factors as leaching rate into the soil, runoff, toxicity from skin exposure, consumer risk, toxicity to birds and fish and duration of the chemical in the soil and on the plant. They also looked at how well each pesticide targeted aphids without harming their predators. However, Marrone points out, “direct contact tests against natural enemies in the lab is not the best way to see the effects of a pesticide on a natural enemy because it does not measure biodegradability or longer term effects in the field,” she said.
While Marrone agrees that just because something is natural does not mean it is safe, she suggests the study gives no reason for organic farmers or consumers to be concerned. “Biopesticides are highly regulated and must go through a series of ‘tox’ and ‘ecotox’ studies; this research is no cause for alarm.”