For all the promise of crops genetically modified to resist pests, the miracles of the laboratory are only good until the bugs outsmart them.
Mark Whalon, a Michigan State University entomology professor, says that farmers and those marketing genetically modified seeds shouldn't become complacent because so far there has been no documented evidence that insects have developed resistance to crops engineered to repel them.
Instead, in a presentation at the 222nd National Conference of the American Chemical Society (ACS) on Wednesday, Aug. 29, he 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 ACS presentation "Insect resistance to GMOs: What have we learned?" explores speculation on whether pests will evolve to defend themselves from crops that produce defenses against them. Insects and mites already have proven deft at developing resistance to applied insecticides, with 540 arthropods resistant to more than 310 insecticides and miticides.
These speculations and deductive 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. Otherwise, we will select a strain of resistant bugs to destroy or mitigate the value of a promising new technology."
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 happily 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."
Source: Michigan State University, August 29, 2001