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Take command of pestilence

You know what “pestilence” is, right? On today’s farms, it’s herbicide-resistant weeds, insecticide-resistant bugs and — for some farmers — GMO contamination. All of this was talked about at the recent GMO 101 research tour hosted by Penn State University’s College of Agricultural Sciences.

Take command of pestilence

You know what “pestilence” is, right? On today’s farms, it’s herbicide-resistant weeds, insecticide-resistant bugs and — for some farmers — GMO contamination. All of this was talked about at the recent GMO 101 research tour hosted by Penn State University’s College of Agricultural Sciences.

All three concerns arose, at least in part, due to farmers putting a higher priority on convenience. And that can be remedied for the most part by farmers themselves.

Eighty to 90% of today’s corn hybrids are transgenic — containing genetic traits inserted from other plants, bacteria or viruses. The traits are expressed via improved drought tolerance and control of insects, weeds and diseases.

With corn, for instance, the genetic engineering shrinks corn’s inbred development cycle from seven years to three, notes Greg Roth, Extension agronomist at Penn State. “This biotech tool is being used to solve some of today’s most difficult and costly crop production problems.”

Good news ... bad news

Bt hybrids helped solve developing European corn borer resistance problems with soil insecticides. “They’ve worked so well that corn borer populations were driven down to almost an endangered species,” says entomologist John Tooker.

Soil insecticide use was greatly reduced. Other crops — tomatoes, for instance — also benefited.

Bt toxins also helped reduce western corn rootworm populations. The transgenic trait allowed expansion of continuous corn across the Corn Belt. While it boosted grower flexibility, it was at the expense of crop rotation and Integrated Pest Management.

Then rootworm resistance to Bt hybrids targeting ECBs began developing due to weak gene expression. This year, damaging populations of rootworms suspected to be resistant to some Bt strains have been found in three Pennsylvania counties and threaten farmers growing continuous corn.

To complicate the situation, Tooker contends Bt hybrids targeting belowground pests indirectly increased use of neonicotinoid insecticide-treated seed. Evidence is growing that the nontarget influence of neonicotinoids and residue buildup in soils are contributing to the decline of pollinators.

Seed treatments also kill other beneficials, including brown beetles that control slugs — Pennsylvania’s biggest insect problem in corn and soybeans in conservation tillage, adds the entomologist.

“This isn’t a GMO problem,” stresses Tooker. “It’s a product-management problem.”

The herbicide resistance dilemma

Weeds evolved and naturally mutated on their own long before crop tolerance was genetically engineered into corn and soybeans. Concern over triazine- and ALS-resistant weeds predated glyphosate and GMO crops, points out Dwight Lingenfelter.

How herbicides are used “causes weeds to evolve,” explains the Penn State weed specialist. “Economics and convenience drive farmer decisions, and have led to the demise of integrated weed management.”

Most of today’s herbicides are 20 years old. Most new products are simply reformulations or premixes of existing active ingredients. “That’s why we strongly recommend integrated weed management strategies in addition to using herbicides with at least two modes of action,” adds the weed specialist. “We need new modes of action. But today, if a company comes up with one, it takes many millions of dollars and at least 10 years to get it to market.”

How farmers use GMO technology is the problem — not the technology itself, insists Lingenfelter. Because of the growing weed resistance problem to herbicides, he says there’s already industry talk of mandating management resistance via seed technology-use agreements.

Key Points

Rising insect and weed resistance isn’t a GMO problem.

Farmer convenience has “driven over” IPM stewardship.

The biotech industry may consider mandating resistance management.

Better manage your GMO corn

Seed technology use agreements spell out how GMO varieties can and can’t be used, says Ross Pifer, director of Penn State’s Ag Law Resource and Reference Center. But, he adds, enforcement is “iffy if a farmer doesn’t sign it. A lot of unintentional misuse and contamination issues haven’t yet been sorted out.”

He suggests the stewardship agreements can be improved, perhaps by limiting the number of years of continuous corn. Where pollination contamination concerns exist with neighboring fields, buffer zones between GMO crops and the property edge could be employed.

That’s tougher to do with refuge-in-a-bag seed. But as Penn State entomologist John Tooker points out: “With Bt corn hybrids at close to $400 a bag, growers have incentive to save $150 a bag with non-Bt seed, and use that corn as a refuge and a pollination contamination barrier.”

Guidelines have been established by seed certification agencies in some states to protect identity-preserved corn from cross-pollination. Some require non-GMO IP corn to be planted at least 660 feet from GMO corn. That’s to keep GMO contamination at no more than 0.5%, according to Peter Thomison, corn agronomist at Ohio State University.

Field size also has a bearing on contamination risks. But Ohio State and University of California studies suggest 150 feet is a reasonable isolation distance to limit cross-pollination of non-GMO corn by GMO pollen to less than 1%.


RESISTANCE CHEWED DOWN: Penn State’s John Tooker shows the evidence of severe western corn rootworm damage on Bt corn found in three Pennsylvania counties.

This article published in the November, 2014 edition of AMERICAN AGRICULTURIST.

All rights reserved. Copyright Farm Progress Cos. 2014.

Crop Management

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