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Organic pesticides not always the “greener” choice

Study shows some organic pesticides have a greater impact than conventional controls

David Kuack | July 6, 2010

A product that is labeled organic doesn’t necessarily mean it’s environmentally friendly. A study conducted by researchers at the Univ. of Guelph showed that some organic pesticides can have a greater environmental impact than conventional pesticides because the organic product may require larger doses. The study has been published in PloS One.
Researchers compared the effectiveness and environmental impact of organic pesticides with those of conventional and reduced-risk synthetic products on soybean crops. The study involved testing synthetic pesticides (2 commonly-used conventional products and 2 new reduced-risk pesticides), a mineral oil-based organic pesticide and a product containing Beauveria bassiana fungus that infects and kills insects. These 6 products were compared for their environmental impact and effectiveness in killing soybean aphids. Field tests were also conducted on how well each pesticide targeted aphids while leaving lady beetles and insidious flower bug predators unharmed.
“We found the mineral oil organic pesticide had the most impact on the environment because it works by smothering the aphids and therefore requires large amounts to be applied to the plants,” said environmental sciences professor Rebecca Hallett.
The mineral oil-based and fungal products were less effective than the synthetic pesticides because they also killed aphid predators, which are important regulators of aphid population and growth. Hallett said the predators reduce the environmental impact because they naturally protect the crop, reducing the amount of pesticides that are needed.
“In terms of making pest-management decisions and trying to do what is best for the environment, it’s important to look at every compound and make a selection based on the environmental impact quotient rather than if it’s simply natural or synthetic,” Hallett said. “It’s a simplification that just doesn’t work when it comes to minimizing environmental impact.” 
 
Pictured: A study of conventional and organic pesticides showed that product selection should be based on the environmental impact quotient rather than whether the product is natural or synthetic.
Photo by Michael Potter, Univ. of Kentucky
 

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