Organic pesticides not always ‘greener’ choiceJune 23rd, 2010 - 7:02 pm ICT by IANS
Washington, June 23 (IANS) Organic pesticides can have a higher environmental impact than conventional pesticides as the organic product may require larger doses, says a University of Guelph (UG) study.
Rebecca Hallett, UG environmental sciences professor and doctoral candidate Christine Bahlai compared the effectiveness and environmental impact of organic pesticides to those of conventional synthetic products on soybean crops.
“The consumer demand for organic products is increasing partly because of a concern for the environment. But it’s too simplistic to say that just because it’s organic, it will be better for the environment,” Hallett said.
The study involved testing six pesticides and comparing their environmental impact and effectiveness in killing soybean aphids - the main pest of soybean crops across North America.
The scientists examined four synthetic pesticides: two conventional pesticides commonly used by soybean farmers and two new, reduced-risk pesticides. They also examined a mineral oil-based organic pesticide and another product containing a fungus that infects and kills insects.
The researchers used the environmental impact quotient, a database indicating impact of active ingredients based on such factors as leaching rate into 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 conducted field tests on how well each pesticide targeted aphids while leaving their 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,” Hallett said.
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.
These predator insects reduce environmental impact because they naturally protect the crop, reducing the amount of pesticides that are needed, she added, said a university release.
“Ultimately, the organic products were much less effective than the novel and conventional pesticides at killing the aphids and they have a potentially higher environmental impact,” she said.
These findings were published in PloS One.
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