IL Researcher Tracks Bt Trait Overuse

High corn prices are leading many growers to plant corn every year and to overuse pesticides and other bug-killing technology to maximize yields, researchers report.

In many instances, pesticides are applied without scouting fields to see if they are needed, violating a bedrock principle of integrated pest management. The result is a biological diversity desert in many corn and soybean fields in the agricultural Midwest, and signs that the surviving insects are becoming resistant to several key bug-fighting tools now available to farmers.

University of Illinois crop sciences professor Michael Gray and his colleagues conducted a survey of corn and soybean pests in 47 counties in Illinois from late July to early August in 2011, and found densities of some key insect pests to be at zero or near zero in many counties.

“I’ve never seen anything like it in 22 years of doing this kind of research,” Gray said. “From an insect diversity perspective, it’s a biological desert in many of those fields.” Even western corn rootworm adults (which normally lay their eggs in cornfields in late summer) were difficult to find in many counties, he said.

In part, these low numbers are the result of environmental conditions – particularly wet springs – the past few years, Gray said. However, the widespread use of Bt-corn hybrids, which produce one or more insecticidal proteins, and the common practice of broadcasting mixes of insecticide and fungicide on corn and soybean fields also plays a role, he said.

And yet, when Gray asks farmers at growers’ meetings if they plan to use Bt corn again this year, a huge majority says yes.“Many producers indicate that in order to have access to high yielding germplasm, the use of Bt hybrids is essential,” Gray said. “It is likely that many growers also will use a soil insecticide at planting, even though a Bt hybrid will be used.” This goes against decades of advice from researchers like Gray who argue for integrated pest management – the careful assessment of bug populations to determine what, if any, treatments are needed, and the use of changing tactics against adaptable pests such as the western corn rootworm and the European corn borer, either of which could devastate corn yields.

“We ask them to consider rotation with soybeans, to spray only when insects are present at levels that are likely to affect yield, and to not use Bt every season, or if they do, to get a different type of Bt corn, one that expresses a different Bt protein,” Gray said.

But instead of using integrated pest management, growers are relying on what he calls “insurance pest management,” throwing everything in their arsenal at the bugs to protect their crop, year after year.

“For corn in Central Illinois, the average non-land costs – things like fertilizer, seed, crop insurance and machinery – come to about $513 an acre,” Gray said. Cash rent can add another $325 an acre for high-yield ground, he said. “So I think a lot of the growers see $20 to $25 dollars to apply a soil insecticide as pretty cheap insurance to protect that $850 investment.”

Landowners are raising rents in this competitive arena, some lenders encourage growers to do everything in their power to protect their yields, and federal incentives have lowered the cost of crop insurance for growers who use Bt corn, Gray said. So there are a lot of reasons for farmers to keep doing what they have been doing.

Most growers are not likely to be alarmed by the low number of bugs, but will instead see it as proof that their strategy works, Gray said. Other evidence, however, suggests that the short-term benefits will lead to unanticipated – and undesirable – consequences.

Researchers are already finding failures of Bt corn against the western corn rootworm in Iowa, Illinois, Minnesota and Nebraska, for example. In a study published in 2011 in the journal PLoS ONE, Aaron Gassmann and his colleagues at Iowa State University demonstrated that the offspring of western corn rootworms from rootworm-damaged cornfields in Iowa were less susceptible to a particular Bt toxin (Cry3Bb1, the type of Bt in use in the damaged fields) than the control population.

Gray has seen the same kind of severe rootworm damage in Illinois fields planted with the Cry3Bb1 variety of Bt corn, and he is collaborating with Gassmann on a new study of the Bt failures in Illinois. As yet, the researchers have not confirmed the cause of these Bt failures and are working to determine the mechanism.

“Like the fields Gassmann studied in Iowa, the failures here in Illinois are in fields planted in continuous corn for many years with no crop rotation, using that same Cry3Bb1 Bt protein over and over again,” Gray said.

Growers’ confidence in Bt corn probably stems from its great success against the European corn borer, a pest accidentally brought to the U.S. in the early 1900s. The insect arrived in Illinois in the late 1930s.

“It was a devastating pest,” Gray said. “It was a major yield robber.”

In a 2010 paper in Science, Gray and colleagues from several Midwestern universities reported that the introduction of Bt corn in 1996 led to a profound and lasting reduction of the European corn borer across the upper Midwest.

This success was in large part due to two factors, Gray said. First, it was relatively easy to get high levels of the Bt proteins in above-ground corn tissues, on which corn borers feed. And second, regulators required farmers who used Bt corn to provide large buffer zones, called refuges, planted with non-Bt corn. The refuges would supply a lot of Bt-susceptible insects to mate with those that survived exposure to Bt and were thus resistant to the toxin, to reduce the development of Bt-resistant strains.

Western corn rootworm larvae do the most damage to roots, however, and expression of Bt toxins in roots is much lower than in above-ground tissues. This means that the rootworms are getting a much lower dose of specific Cry toxins than the corn borers do, Gray said. Add to that the fact that some growers are ignoring the buffer requirement while also planting Bt corn year after year, he said, and you’ve got a recipe for resistance.

“We might not be having this conversation if corn was $3 a bushel and growers were asking us where to put their limited resources,” he said. “But with these high commodity prices the notion of adding inputs to squeeze out a couple of more bushels seems like cheap insurance.”

Gray will present his latest findings at the International Integrated Pest Management Symposium on March 27-29, 2012, in Memphis, TN.

Leave a Reply

Seed/Biotech Stories

Seed/BiotechSyngenta Delivers Two New Winter Wheat Varieties To Eastern Corn Belt
August 6, 2014
Adding to its portfolio of AgriPro brand wheat varieties, Syngenta introduces SY 007 and SY 474 soft red winter wheat varieties. Read More
Seed/BiotechWater Optimized Seed Flowing Freely
April 1, 2014
As the demand for ag to diminish its water use while maintaining high yields and crop quality increases, three companies are leading the movement to grow more with less water. Read More
Seed/BiotechBayer Applies For Seed Treatment That Protects Against Sudden Death Syndrome
February 26, 2014
If approved, ILeVO seed treatment would be the first product to provide breakthrough protection for soybean seedlings from the soil borne pathogen Fusarium virguliforme, the fungus that causes SDS. Read More
Seed/BiotechSeed Still Central
November 1, 2013
Advancing genetics continue to make seed the crop variable that calls the shots for the season. Read More

Trending Articles

Crop InputsPlatform Specialty Products To Acquire Arysta LifeScience
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More
Seed/BiotechMonsanto Offers New Support For Ferguson, Area Communities
October 8, 2014
Monsanto Co. has committed $1 million in new support for several collaborative efforts in Ferguson, MO, and surrounding communities in North St. Louis County. Read More
Seed/BiotechUnapproved Genetically Modified Wheat Found In Montana
October 3, 2014
USDA reports that one year after discovery of Monsanto's unapproved wheat in a single Oregon field disrupted U.S. wheat export sales, the GMO wheat has again been found in Montana. Read More
Equipment2014 Product Of The Year Voting
September 19, 2014
The deadline to vote for the 2014 CropLife IRON Product of the Year is October 31. Please cast your vote today to help us determine the winner. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More

Latest News

InsecticidesValent U.S.A., MGK Form Marketing Agreement
October 24, 2014
Valent has formed an agreement with Minneapolis-based MGK to manage the marketing and sales of MGK’s crop protection line of insect control products within the U.S. beginning April 1, 2015. Read More
StewardshipFlorida’s 4R Advocate Keeps Improving
October 24, 2014
Florida farmer Alan Jones uses the 4R principles of nutrient stewardship as the core of his fertility program, which allows him to maximize production and keep costs in check. Read More
Seed/BiotechMonsanto Named One Of The World’s Best Multinational …
October 23, 2014
Monsanto ranked No. 8 in the world’s largest annual study of workplace excellence that identifies the top 25 best multinational companies in terms of workplace culture. Read More
Crop InputsArysta Hires Former Agri-Chem, CPS Employee For Delta S…
October 23, 2014
New Territory Sales Manager Mark Peel’s primary role will focus on working with growers regarding fungicides in Louisiana, Mississippi, Arkansas and Tennessee. Read More
CropLife 100GROWMARK Announces Appointments In Plant Food Division
October 22, 2014
GROWMARK, Inc. has announced the three key staff changes in its Plant Food Division. Read More
CropLife 100GROWMARK Appoints New VP Of Finance And Risk Management
October 22, 2014
Wade Mittelstadt has been named GROWMARK Vice President, Financial and Risk Mangement, effective December 1, 2014. Read More
FungicidesEPA Approves BASF In-Furrow Corn Fungicide
October 22, 2014
Field trials show Xanthion In-furrow fungicide provides more rapid emergence, extended residual control and improved seedling health than untreated crops. Read More
EquipmentAgraScout App Available At No Cost To Universities
October 21, 2014
AgraScout, a fast and easy to use mobile crop scouting app, is now available at no cost to University students, Read More
LegislationNew Farm Bill Program To Provide Relief To Farmers Affe…
October 21, 2014
The USDA has implemented a new Farm Bill initiative that will provide relief to farmers affected by severe weather, including drought. Read More
ManagementGreenfield Scholars Program Aims To Sustain Agronomy Wo…
October 21, 2014
The program encourages talented students to study agronomy, crop and soil sciences while cultivating networks to develop the necessary workforce to sustain the profession. Read More
Paul SchrimpfPrecision Ag: Taking It To The Hill
October 21, 2014
A new coalition took the good news message of precision agriculture to Washington, DC, last month. Read More
ManagementUSDA Awards $18 Million In Small Business Research Gran…
October 21, 2014
The grants will provide high quality, advanced research and development that will lead to technological innovations and solutions for American agriculture. Read More
FertilizerCF Industries Terminates Merger Discussions With Yara I…
October 21, 2014
CF Industries Holdings and Yara International have terminated their discussions regarding a potential merger of equals transaction. Read More
Seed/BiotechSyngenta Ranked A Top 10 Biotech Employer For Third tim…
October 20, 2014
Syngenta ranked in the top 10 among the world’s top biotech employers, according to an annual survey conducted by Science magazine. Read More
CropLife 100Wheat Growers Break Ground For New Facility At Kennebec
October 20, 2014
Wheat Growers has broke ground for a state-of-the-art shuttle loader grain handling, fertilizer and agronomy facility in Kennebec, SD. Read More
FertilizerVerdesian Life Sciences Signs Agreement With Los Alamos…
October 20, 2014
Verdesian Life Sciences has signed a licensing agreement with Los Alamos National Laboratory to develop and market LANL’s latest nitrogen enhancement technology for plants. Read More
MicronutrientsStoller Group Announces Groundbreaking At New Office Bu…
October 20, 2014
Jerry Stoller, founder and president of Stoller Group, announced the groundbreaking at the site of the company’s future headquarters in Read More
Crop InputsBioSafe Systems Opens New Production Facility In Nevada
October 20, 2014
BioSafe Systems has completed construction of a state-of-art production facility in Sparks, NV, for its line of activated peroxygen products. Read More