More problems may lie ahead for engineered rootworm control genes. A second industry strategy is to develop new types of controls that do not rely on Bt toxins. For example, a recently discovered type of genetic material, called interfering RNA (or RNAi) is being touted, and Monsanto now has an application for approval at USDA. But some RNAi may harm important beneficial insects. And eventually, rootworms may develop resistance to RNAi too, if it is approved.
Some beneficial insects, called “natural pest enemies,” reduce pest levels and the need for insecticides. Harm to these helpful insects may be more likely to occur from transgenic rootworm controls than Bt toxins aimed at corn borers. This is because rootworms are beetles, and they’re related to many beneficial insects, such as ladybird beetles, which are then more likely to become collateral damage. In fact, in 2012, scientists at Cornell University found that rootworm Bt toxin is likely to be harming several important species of beneficial beetles in GMO corn. By contrast, corn borer is in the butterfly and moth group, and there are fewer beneficial insects in this group that protect row crops.
A better approach, and one recommended by the PNAS paper, is crop rotation—growing different crops on the same acreage in succession from year to year. This is a common practice of organic farmers and a common component of other agroecological farming methods. It is also incredibly effective for controlling rootworms in most places. In fact, where long rotations are used, no chemical insecticides or Bt toxins are needed to control these pests.
The Problem is Monoculture, and GMOs are Making it Worse
Of course, using agroecology has many other benefits, and can be as or more profitable than industrial monoculture, as I have written about before. These practices help farmers reduce water pollution from fertilizers and increase soil fertility and crop resilience, while maintaining or increasing productivity.
But GMO crops, along with ill-conceived crop subsidies and a skewed research agenda focused on industrial agriculture, have encouraged the opposite—more monoculture. Simply recommending that we change farming practices, without changing the policy and other infrastructure that encourages monoculture, will not foster the sustainable agriculture that we need.
Growing the same crops year after year in the same fields is a recipe for big pest problems, from weeds and insects to diseases. And using the same simple methods to kill pests and weeds on monoculture crops is merely a recipe for more pesticides. Monoculture promotes higher numbers of pests, because the pests adapt to a particular crop when they can find it in the same place from year to year.
More pests mean a higher number of rare, naturally-occurring pest genes that confer resistance to chemical pesticides or Bt toxins. When the same pesticide is used over and over, resistant pests survive and multiply quickly. This practice is also what has caused the epidemic of glyphosate- or “Roundup-resistant” weeds now plaguing US farmers. That is no coincidence.