Encouraging Good Insects And Limiting The Bad Ones

No-till and biodiversity can preserve beneficial insect populations that naturally control crop pests, and possibly reduce insecticide usage, says a USDA expert.

The prevalent attitude that the only good bug is a dead bug is leading agriculture down a perilous road, says Jonathan Lundgren, an entomologist at the USDA-ARS laboratory in Brookings, S.D.

Lundgren is focused on preserving and promoting the beneficial insects that prey on the pests that chew into crop yields.

Just as some weed species have developed herbicide resistance, insects can develop insecticide resistance, he says. In fact, the world’s most expensive pest to manage, the western corn borer, has developed field-evolved resistance to Bt corn in some areas, he says.

The prevalence of Bt crops, along with rising insecticide usage — especially in the form of seed treatments — has placed tremendous pressure on both target and nontarget insect populations, Lundgren adds.

Dropping Pest Levels. Ironically, the chemical insect onslaught continues, even when problem pest populations fall well below economic thresholds.

In 2009 and 2010, Lundgren and his team sampled 53 farms in eastern South Dakota. The fields were more than 10 acres in size, planted to non-Bt corn and had no insecticides applied.

What he found was a very low density of target pests — 0.2 to 0.7 western corn rootworm adults and 0.04 to 0.12 European corn borers per plant. Even when all caterpillars were included in the count, only about 1 caterpillar per 5 plants was found.

“Because Bt corn is so incredibly effective at killing these target pests, we’re experiencing what entomologists call area-wide suppression,” Lundgren says. “We have driven the population of target…

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Mark Parker

Contributing Editor

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