Rootworms Show Resistance To Bt Corn

Isolated findings of resistant rootworms in Iowa emphasize that planting a refuge is more critical than ever for maintaining the durability of Bt corn, a Purdue Extension entomologist says.

Bt corn does not kill all larva that feed upon it, and very slight feeding damage from corn rootworm is typical, said Christian Krupke. But after researchers at Iowa State University were alerted to high levels of feeding damage in some fields, they began to test Bt corn hybrids that expressed the Cry3B1 toxin. They found that rootworms from those fields were able to survive exposure in the lab.

“This is not a cause for alarm for Indiana producers, and it was something that we suspected would occur eventually,” Krupke said. “Producers should keep doing what they are doing for now as the vast majority of Bt continues to perform well for producers. This is more of a warning to be vigilant.”

Currently, other Bt toxins appear to be effective against the pest.

He said growers in areas with histories of high rootworm pressure should scout fields in early to mid-July to look for lodged corn and adults, which are gold and black beetles. Farmers seeing anything unusual should dig up the plants and look for root damage. By August or later, roots can regrow and disguise damage.

If farmers see widespread damage, they should contact their seed representatives to determine if their corn was supposed to be protected by the Bt technology.

“Producers should only be more concerned if there is considerably more damage than usual,” Krupke said. “Also, it’s worth a second look to ensure they aren’t looking at refuge plants instead of the hybrid.”

Growers who think they have a potential problem should report it to their Purdue Extension county educators. All farmers should follow best management practices when using any hybrid varieties targeting pests.

The most important thing corn growers can do this season and in the future is follow refuge guidelines, Krupke said. Refuges develop a population of susceptible adults and allow mating between those and any potentially resistant beetles that emerge from Bt plants. Compliance with refuge recommendations has declined in recent years.

“The refuge is crucial as the Bt hybrids do not kill all larva; some will inevitably become adults. We don’t want those survivors to mate with one another and pass on the traits that helped them survive,” Krupke said. “By limiting the number of mating adults we have, we can hopefully dilute the genetics of these resistant individuals and prevent the population from becoming resistant.”

Rotating with soybeans, and diversity in cropping systems in general can also delay resistance. Fields with continuous Bt corn and high rootworm pressure should be closely monitored, as they provide the greatest pressure for resistance development.

For more information and a link to the Iowa State article, read the Aug. 5 issue of Purdue Pest and Crop Newsletter at http://extension.entm.purdue.edu/pestcrop/.

(Source: Ag Answers)

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
Top 100 Articles
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Match Made In Deviation
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
CropLife 100The Andersons Acquires South Dakota Plant Nutrient Manufacturer Kay-Flo
May 20, 2015
The Andersons, Inc., ranked No. 22 on the CropLife 100, has purchased Kay Flo Industries of North Sioux City, SD. “This Read More
CropLife 100North Central Farmers Elevator, Wheat Growers Unification Approved By Board, Still Awaits Member Approval
May 13, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have voted to approve the Unification Read More
CropLife 100AgGateway’s Barcoding Initiative Progressing Nicely
May 8, 2015
According to legend (or Wikipedia), the first step towards modern bar codes came back in 1948, when Bernard Silver, a Read More
CropLife 100Pinnacle Agriculture Acquires Minnesota Retailer
April 14, 2015
Pinnacle Agriculture Holdings, LLC, ranked No. 6 on the CropLife 100,  has successfully acquired Liebl Ag, LLC in Ada, MN.  Read More
Latest News
Crop InputsLand O’Lakes, United Suppliers To Merge Crop Inpu…
June 29, 2015
Land O’Lakes, Inc. and United Suppliers, Inc. of Ames, IA, today announced their intent to merge their crop inputs businesses. Read More
FungicidesHelena To Distribute Unique Summit Agro Fungicide
June 29, 2015
RANMAN 400 SC fungicide, the only fungicide with a FRAC group 21 designation, is now part of the innovative Summit Read More
Eric SfiligojIARC Targets 2,4-D In Latest Report
June 29, 2015
The International Agency for Research on Cancer (IARC) has struck again. Earlier this year in March, this agency of the Read More
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Ma…
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
EquipmentCase IH Launches New Precision Air 5 Series Carts
June 29, 2015
Case IH recently introduced its new Precision Air 5 series air carts, developed to get the most from every plant’s Read More
InsecticidesVestaron Biopesticide Approved In California
June 29, 2015
Vestaron Corporation, a developer of insect control products derived from naturally occurring peptides, today announced that its VST-006330-EP biopesticide has received Read More
InsecticidesValent’s Zeal SC Miticide Receives EPA Approval
June 29, 2015
Valent U.S.A. Corporation announced today that Zeal SC Miticide has been registered by EPA with a new liquid formulation that Read More
Retail FacilitiesUnited Prairie Increased Plant Productivity With Junge …
June 29, 2015
Since 1979, Junge Control continues to provide ag retailers with highly accurate fluid and dry ingredient measuring, mixing and tracking Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
ManagementAsmark Training Center Visit & A Merger No Go
June 25, 2015
CropLife Editor Eric Sfiligoj talks about a visit to the Ford B. West Training Center and the failure of the Read More
Crop InputsWinField: Here’s What We’re Seeing So Far T…
June 25, 2015
One of the most important things you can do throughout the season to help increase yield potential is to ensure Read More
Valent, Commodity Classic 2015
Industry NewsValent Garners FFA Honor
June 23, 2015
Valent U.S.A. Corporation today announced it has been named a 5-star member of the National FFA Foundation. This includes an Read More
Nester Ag intern Brad Nester
Crop InputsOhio NRCS’ New Conservation Practice Standard For Gypsu…
June 22, 2015
Ohio farmers wishing to use gypsum to improve soil quality now have access to technical information and possible financial assistance Read More
Industry NewsWest Central Creates New Executive Team
June 22, 2015
West Central Distribution, LLC officially announced the development of an executive team comprised of Dale Engan, chief executive officer; Michael Read More
MicronutrientsVerdesian Life Sciences Invests In People, Agricultural…
June 22, 2015
In mid-February, the USDA released its new 10-year agriculture projections. While the numbers are new, the theme was consistent. The Read More
Young corn plants
Crop InputsStudy: Crop Rotation Has Positive Impact On Soil Microb…
June 22, 2015
A study authored by Michigan State University (MSU) Department of Plant, Soil and Microbial Sciences assistant professor Lisa Tiemann is Read More
Crop InputsIndiana NRCS Unveils Interim Gypsum Practice Standard
June 22, 2015
Indiana farmers wishing to use gypsum to improve soil quality as part of on-farm conservation programs now have access to Read More
ManagementInside Monsanto’s Bid for Syngenta
June 18, 2015
Monsanto’s possible buyout of Syngenta could send ripples through the retail chain. Learn the latest developments with Retail Week guest Read More