Insects May Need Refuges from Biotechnology

CHICAGO, Illinois, August 30, 2001 (ENS) - Crops which have been genetically modified to resist pests are only useful until the bugs outsmart them, developing their own protections against the toxins produced by the plants. A Michigan entomologist argues that some crop eating insects must be protected in order to keep them all from becoming resistant to engineered crops.


Genetically engineered Bt corn uses a gene from the toxic soil bacterium Bacillus thurigiensis to produce a substance toxic to the European corn borer, reducing crop damage like this (Photo courtesy Agricultural Research Service)
About one third of U.S. cornfields are now planted with genetically engineered varieties, and about half of the soybeans the U.S. grows are engineered. Many engineered crops are designed to produce their own pesticides: toxins that make the plants deadly to the insects that eat them.

The engineered crops are intended to save farmers money, by reducing crop damage from pests and reducing the amount of chemical pesticides they need to apply to their land.

But some biologists and agricultural experts warn that the rising popularity of engineered crops could have an expensive side effect. Just as insects and other crop pests can develop resistance to traditional pesticides, they may become resistant to engineered crops, producing so called "super pests" that will inflict severe damage on the nation's increasingly engineered food supply.


Entomologist Mark Whalon (Photo courtesy Michigan State University)
Mark Whalon, a Michigan State University entomology professor, says that farmers and those marketing genetically modified seeds should not become complacent just because there has been no documented evidence that insects have developed resistance to crops engineered to repel them.

Instead, in a presentation at the annual meeting of the American Chemical Society in Chicago this week, Whalon said precautions should be taken to explore ways to combat resistance to genetically modified organism (GMO) crops before the bugs develop it.

"We'd like to think that science could manage resistance, but in truth, historically we've been pretty ineffective," Whalon said. "I think what's going on in the big GMO crops - corn and cotton - is that growers haven't yet gotten a high enough percentage of GMO plants in the field such that sufficient selection pressure has been mounted against the pests for resistance to develop."

Whalon's presentation - "Insect resistance to GMOs: What have we learned?" - explored speculation on whether pests will evolve to defend themselves from crops that produce defenses against them. Insects and mites have already proven deft at developing resistance to applied insecticides, with 540 arthropods now resistant to more than 310 insecticides and miticides.


Half the soybeans planted in the U.S. in 2000 came from genetically modified seeds (Photo by Scott Bauer, four photos courtesy Agricultural Research Service)
These arguments have resulted in the first ever requirement by U.S. Environmental Protection Agency for resistance management plans as a part of the GMO registration process.

Whalon is a proponent of working now to head off resistance in the field by learning to live with some of the insects. He argues that a certain number of crop eating pests need to be treasured - protected for the susceptibility genes they pass on to the next generation.

"It has never been good just to kill everything you can," Whalon said. "We should be trying to preserve a sufficient number of insects that are susceptible to the GMO crops."

"These bugs that normally would be killed need to be allowed to survive so they can provide susceptible genes to the population pool," explained Whalon. "Otherwise, we will select a strain of resistant bugs to destroy or mitigate the value of a promising new technology."


This bioengineered barley carries a gene that may help the plants resist attack by barley yellow dwarf virus (By Jack Dykinga, two photos courtesy Agricultural Research Service)
The process of letting a few otherwise doomed bugs survive and pass their vulnerability or "susceptibility" on to future generations is called the "refugia strategy" - the practice of providing a GMO free refuge for the bugs to grow, develop and breed. Give the more fragile, yet genetically valuable pests a place to call their own - even if they munch away at the crops in a minor way - and they will pay farmers and society back for many, many years to come.

The practice of refugia is still experimental - and can be a tough sell to farmers skeptical of showing mercy to any crop eating pests.

"Susceptibility is a natural resource," Whalon said. "Just like there's only so much water and air, there's only so much susceptibility to be grabbed up and exploited. It's a natural resource that could be critical to the future of feeding generation of people to come."