Bugs, fungi, and nematodes deployed to battle corn rootworm

Researchers are turning to natural solutions like nematodes, spiders, and cover crops to fight the notoriously destructive rootworm in corn crops. “Western corn rootworm has evolved resistance to nearly every chemical and biotech tool deployed against it in the past few decades,” including Monsanto’s genetically modified Bt corn, says The Progressive Farmer.

Originally developed by Monsanto in 2003, Bt corn was genetically modified to produce the soil bacteria Bacillus thuringiensis, which the company promised would kill key pests, including rootworm. However, almost from the very start, Monsanto had evidence that rootworm was developing resistance to the bacteria.

Stonewalling by Monsanto delayed what might have been an effective action to slow the spread of resistance, but would have likely come at the cost of reduced sales of Monsanto’s expensive seed,” says Civil Eats. In 2011, resistance was indeed confirmed. And scientists have struggled to defeat the insect ever since.

But now, researchers think Mother Nature may have a solution. Early tests by Cornell University entomologist Elson Shields have shown that nematodes—tiny worms in the soil— are just as effective as the bacterium in genetically-modified Bt corn at killing rootworm. Encouraged by nematode research, Monsanto is sponsoring its own research on them in the Midwest with the help of USDA scientists in Columbia Missouri. Meanwhile, Jonathan Lundgren, an independent agroecologist and entomologist, who has spent more than a decade on the rootworm problem, is experimenting with cover crops as a way to provide habitat for rootworm predators like spiders, ants and centipedes.

“Lundgren’s work revealed that rootworm blood has a repellent quality that keeps many biting insects at bay. However, sucking insects like spiders and ants appear to feast on the rootworm quite happily,” says Progressive Farmer, adding that covercrops offer these insects shelter and a place to breed — in addition to returning vital nutrients to the soil.

The Nebraska Corn Board is also funding research on fungal strains that may be strong enough to kill rootworm.

Some scientists have pointed out that rootworm is a symptom of a weak agricultural system based on monocultures. “We are creating our own rootworm problems by reducing biodiversity in our cornfields,” Lundgren said. “When you have a diverse insect community, then rootworms aren’t an issue anymore.” Defeating the pest could well depend on how well farmers can return that insect diversity to their crop fields.