Engineered Pest Problems

, former senior scientist, Food and Environment | August 30, 2011, 5:13 pm EDT
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Genetically engineered crops contain combinations of two widely successful types of genes—glyphosate herbicide resistance that allows spraying the weed killer onto crops without harming them, and toxins, collectively called Bt, that kill some insect pests. Both are now facing problems that are threatening their usefulness. Weeds that have developed resistance to glyphosate are no longer controlled by the herbicide, and now infest millions of acres of cotton and soybeans in the U.S, causing substantial practical, economic, and environmental problems.

Adult corn rootworm

Adult corn rootworm. Photo: USDA

The GE industry’s solution is to engineer new types of herbicide-resistant crops. But because there are no widely-effective new herbicides, these new crops will be resistant to older, riskier herbicides like 2, 4-D and dicamba, that were some of the first commercial pesticides.

This does not strike me as a new and innovative approach to agriculture for the 21st century.

Now we have the first report of lost effectiveness of one of the two major types of Bt used in corn. This type of Bt, technically called Cry3Bb1, usually kills corn rootworm. Corn rootworm is one of the most destructive insect pests of corn, and more insecticide was used to control it than for any other corn insect pest in the U.S.

The rootworm report follows recent reports of other insects developing resistance to other Bts in cotton in India and corn in South Africa.

So far the resistant rootworms have been found at only a small number of sites in Iowa and Illinois. But unless strong measures are taken to reverse the practices that have led to it, these incidents will be only the beginning.

A recent article by Scott Kilman in the Wall Street Journal covers this issue well, but leaves out some important points.

One is that biotechnology does nothing to encourage ecologically sound agriculture that would address these problems in the innovative and effective ways that are needed. Instead, the industry and many of its supporters have been advocating actions—such as weakening an already limited regulatory system for GE—that could exacerbate these problems.

Regulatory Discretion—or Capitulation?

Not mentioned in Kilman’s article was that EPA invited a group of scientists to provide recommendations about how to prevent rootworm resistance to Bt corn. Instead of following the majority opinion to require strong measures to prevent resistance,  EPA instead listened to the minority of less-cautious scientists and the interests of the biotech industry, and went with a weaker approach. We may be seeing the results of this shortsighted action in the new resistant rootworms.

There are two other types of Bt that still control the new Cry3Bb1-resistant rootworm. But they all share a property that generally makes them vulnerable to resistance: none are effective enough to kill almost all rootworms. The surviving rootworms increase the chance that rare Bt resistance genes will be able to spread. So greater use of the other main Bt, called Cry34/35Ab1, to replace Cry3Bb1 will increase the chance of causing its own resistance crisis before too long. Cry34/35Ab1 was approved several years after Cry3Bb1, so it may take a little time to catch up!

And if entomologists think that farmers, en masse (which is what it takes) will give up products that work well in order to prevent resistance, they should look closely at what has happened with glyphosate resistant weeds. The kinds of practices that could have forestalled resistance have long been known, but instead of using them, we now have millions of infested acres.

If EPA does not use its regulatory authority to do what is needed, history tells us the resistance problem is likely to get much worse.

Kilman mentions a new type of GE called RNA interference (or RNAi for short) for killing pest insects, that may come to the rescue. RNAi shows some promise, but there are lots of hurdles for a new technology like this before it can be successful commercially. It will be years, at least, before it is available to farmers.

And there is no reason to believe that RNAi would not also face resistance problems.

Kilman is apparently not aware of several promising non-GE rootworm-resistant varieties of corn recently developed through conventional breeding by USDA and universities. Funny that we don’t hear about them–they are likely farther along than RNAi. If they are successful, they will be yet another example of conventional breeding matching or exceeding GE.

The issues surrounding pest resistance reveal an agriculture sector with serious problems, despite its high productivity, that need serious solutions.

A Fundamentally Different Agriculture is Needed

Relying on genetic approaches alone to control pests—even conventional breeding—leaves crops vulnerable to numerous problems. We also need to use ecologically sound farming practices that complement genetics.

Briefly mentioned in the WSJ article is the fact that rootworm is not much of a problem if sensible crop rotations are used. Crop rotation is the alternating of the types crops that are planted from year to year, and is a fundamental part of organic farming. Instead most farmers in the Midwest grow nothing but corn or soybeans year after year.

Put another way, rootworm probably would not even be an important pest if it were not for our unnecessary over-dependence on corn.

And long crop rotations reduce more than rootworm damage. They greatly reduce most pests, including other insects, diseases, and weeds, thereby greatly reducing pesticide use as well. Long crop rotations also improve soil fertility, and reduce fertilizer use, cost and pollution. And they can be just as productive as our current corn obsession.

So why aren’t we using them?  Part of the reason is that current policies such as ethanol supports and other subsidies favor corn and a few other crops, and exclude others that could be grown in rotation. And without better government policies—like shifting incentives to support good farming practices—farmers will usually  go for the easiest and cheapest ways to grow their crops. Who can blame them?

But isn’t this what we used to call shortsighted?


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