More Corn Rootworm Resistance To Bt Corn Reported In Illinois

With the addition of three more counties, a total of five Illinois counties have now reported confirmed cases of field-evolved resistance to Bt corn (Cry3Bb1 protein) by Western corn rootworm, and a University of Illinois entomologist said now is the time to move forward aggressively with integrated pest management (IPM) strategies, according to the Illinois Ag Connection.

In August 2012, in cooperation with an Iowa State University lab, Mike Gray said he confirmed resistance in Henry and Whiteside counties in northwestern Illinois. Working with Joe Spencer of the Illinois Natural History Survey and utilizing single-plant bioassays with larvae collected last summer, Gray said resistance to the Cry3Bb1 protein has now also been confirmed in McDonough, Mercer, and Sangamon counties.

The suspected Bt-resistant larvae collected last summer were exposed to a hybrid expressing the Cry3Bb1 protein as well as its corresponding isoline (not expressing the Cry3Bb1 protein), Gray said. Larvae obtained from three control colonies of Western corn rootworms also were used in the bioassays. The control larvae had never been exposed to corn rootworm Bt protein and were provided by the USDA North Central Agricultural Research Laboratory in Brookings, SD.

Gray said there continues to be some controversy regarding the most appropriate procedures (plant-based vs. diet-based bioassays) that should be used to confirm whether or not resistance to a Bt protein has developed by an insect population. Citing a University of Arizona study that defines key terms regarding resistance to Bt crops and pesticides, Gray offered the following definitions that are useful in communicating with producers who have experienced greater than expected levels of damage to rootworm Bt hybrids in their fields.They include:

  • “Resistance: genetically based decrease in susceptibility to a pesticide”
  • “Field-evolved resistance (= field-selected resistance): genetically based decrease in susceptibility to a pesticide in a population caused by exposure to the pesticide in the field”
  • “Practical resistance (= field resistance): field-evolved resistance that reduces pesticide efficacy and has practical consequences for pest control”

“It has become increasingly evident that some producers have experienced a loss of efficacy with some Bt hybrids in their fields in recent years,” Gray said. “To date, most of those fields have been in continuous corn production, and producers have not rotated traits. It’s also clear that ‘practical consequences’ have resulted due to the loss of efficacy associated with some Bt hybrids in problem fields.

“The primary consequence so far has been an escalation in the use of planting-time soil insecticides with Bt rootworm hybrids. This practice may hasten the onset of resistance evolution to Bt proteins as outlined in a paper published last year,” he added.

Other consequences of the evolution of practical resistance by the western corn rootworm has been the increased use of pyramided Bt hybrids, the use of seed blends as a primary refuge strategy, and a reduction in the size of the required refuge — from 20% to 5% for some products.

“The reduction in the refuge size remains troubling for many entomologists, especially in areas of the Corn Belt where resistance has been confirmed to one of the rootworm Bt proteins. Although a seed blend offers many advantages, including ensured compliance as well as improving the chances that Bt-susceptible and resistant adults will mate, increased selection pressure on the one effective Bt protein within a compromised pyramid, may be a primary consequence of a 5% refuge,” he said.

To date, four Bt rootworm proteins have been registered for use in the United States: Cry3Bb1, Cry34/35Ab1, mCry3A, and most recently eCry3.1Ab. Gray said that Aaron Gassmann (Iowa State University) and his colleagues recently published a paper in which they confirmed the field evolution of resistance to the mCry3A protein. In the same journal article, they also confirmed cross-resistance between Cry3Bb1 and mCry3A proteins.

“These findings are troubling from many perspectives. For instance, pyramided Bt hybrids that are used in areas of the Corn Belt where practical resistance to the Cry3Bb1 and mCry3A proteins is a reality, may in fact be relying to a great extent upon the efficacy of Cry34/35Ab1 or eCry3.1Ab to ensure adequate root protection — again, at reduced refuge size requirements (5%),” he said.

Last summer, Gray reported on the failure of some Bt hybrids (Cry3Bb1) to provide adequate root protection in rotated corn in Kankakee and Livingston counties. Spencer will conduct plant-based bioassays on the offspring reared from the adults collected from these fields. Results from these bioassays will be in later this year.

“If the results confirm resistance to the Cry3Bb1 protein, it seems clear that a segment of the Western corn rootworm population can now overcome rotation and this protein. With cross-resistance within this population to the mCry3A protein a possibility, we begin to see how diminished our IPM tool box is for this insect pest,” Gray explained.

“As I have done in the past, I urge producers to implement a long-term integrated pest management approach for corn rootworms. This includes the use of multiple tactics (over time, not all in the same season), such as: use of a more diverse crop rotation system, use of a non-Bt hybrid in conjunction with a planting-time soil insecticide, rotation of pyramided Bt hybrids, and consideration of an adult suppression program in heavily infested fields,” he said.

Leave a Reply

Crop Inputs Stories

Soybean Plant closeup
HerbicidesRegional Listening Sessions Give Farmers A Voice In The Battle Against Herbicide Resistance
February 27, 2017
Both scientists and regulators have had a lot to say about the growing problem of herbicide resistance and how weed Read More
Untreated soybean seed Heartland Coop
Seed/BiotechMarrone Bio Innovations, Groundwork BioAg Bio-stacked Microbial Seed Treatments Result In Increased Yields
February 13, 2017
Marrone Bio Innovations, Inc. and Groundwork BioAg, Ltd have announced successful seed treatment field trials of the world’s first all-biological Read More
Fertilizer Storage
Crop InputsThe State Of The Fertilizer Industry
February 9, 2017
He’s all hat, no horse.” It’s a humorous way of describing a person who tells a good story, but is Read More
Corn Field
InsecticidesArysta LifeScience, DuPont Collaborate On Rynaxpyr Premix Formulations
February 8, 2017
Arysta LifeScience recently announced that it has entered into a global collaboration with DuPont Crop Protection for the development of Read More
Trending Articles
Farmer and aptop
Matt Hopkins10 Warning Signs Your Website Is Grossly Outdated
February 8, 2017
Your Website is often a visitor’s first impression of your ag retail business. A positive first impression can set the Read More
AgriSync
Matt Hopkins17 Agriculture Apps That Will Help You Farm Smarter In 2017
December 9, 2016
Ag professionals are working smarter, not harder, than ever before. Smart farming technologies have enabled them to reduce costs, maximize Read More
R4023 Sprayer, John Deere
CropLife 100Ag Retail Equipment Report: The Green Party Continues
December 7, 2016
In the annual race for sales in the ag retail equipment marketplace, the color schemes for participants are a little Read More
Mike Stern
Precision AgClimate Corp. CEO Talks Retailer Support For Digital Ag
December 1, 2016
CropLife Magazine’s sister publication, AgriBusiness Global, recently sat down with Mike Stern, CEO of The Climate Corp., following the Monsanto subsidiary’s Read More
Precision AgTrimble Debuts End-to-End FMIS Platform
November 28, 2016
October’s inaugural PrecisionAg Vision Conference left this author with many thoughts and things to ponder in the coming months. Probably Read More
CHS Primeland
CropLife 100The 2016 CropLife 100 Report: Reviewing The Many Bulls And Bears Impacting This Year’s Marketplace
November 28, 2016
For virtually all of 2016, the nation was wholly focused on the big Presidential election. Some folks aligned themselves with Read More
Latest News
Soybean Plant closeup
HerbicidesRegional Listening Sessions Give Farmers A Voice In The…
February 27, 2017
Both scientists and regulators have had a lot to say about the growing problem of herbicide resistance and how weed Read More
Greystone Construction built the tension membrane fertilizer storage building (left) and steel seed treater building (right)
CropLife 100Pinnacle Announces Successful Exchange Offer Results An…
February 27, 2017
Pinnacle Agriculture Holdings, LLC has announced today the early tender results of its previously announced offer to exchange (the “Exchange Read More
IEI Barge Fertilizer Potash Port Terminal
EquipmentLegacy Building Solutions Receives Design-Build Merit A…
February 27, 2017
When IEI Barge Services needed a building capable of storing and loading fertilizer, they turned to Legacy Building Solutions to Read More
ManagementSouth Africa Update and the New New Leader G5
February 24, 2017
Editors Eric Sfiligoj and Dan Jacobs discuss the recent visit to South Africa by sister magazine AgriBusiness Global and the Read More
Fall Creek Watershed
StewardshipUpdate: Nutrient Stewardship In Indiana Requires Cool, …
February 24, 2017
Update: The application deadline for NCRS funding has been extended to March 17, 2017. Green leaves sparkle in the sunlight. Trees Read More
Greenleaf Technologies TADF03-D Dual Fan Nozzle
NozzlesSix Greenleaf Nozzles Approved For XtendiMax With Vapor…
February 22, 2017
Greenleaf Technologies has announced that six of its TurboDrop D Series nozzles have been approved for use with Monsanto’s XtendiMax Read More
Winter Wheat
Industry NewsTiger-Sul Hires Manitoba And Eastern Canada Account Man…
February 22, 2017
Tiger-Sul, a global leader in sulphur fertilizers and crop performance products, has announced that sales veteran Trevor Loewen has joined Read More
NFMS 17 Hagie Sprayer
Eric SfiligojThe Read From Louisville: Uncertain
February 22, 2017
By the time this column appears across the country, the annual Commodity Classic will be in full swing. This means Read More
SprayersApache 1000 Series Sprayer Earns 2017 EquipmentWatch Hi…
February 21, 2017
ET Works has been named a winner in the 2017 EquipmentWatch Highest Retained Value Awards program, the industry’s only award Read More
Measuring Bulk Tanks
StewardshipMeister Media Among 2017 Award Winners Presented By The…
February 21, 2017
The Pesticide Stewardship Alliance (TPSA) held its annual conference in San Diego, CA, earlier this month where three awards were Read More
John Reifsteck
CropLife 100GROWMARK’s Reifsteck Earns NCFC Director Of The Y…
February 21, 2017
GROWMARK Chairman of the Board and President John Reifsteck has earned the prestigious Director of the Year Award from the Read More
Roy Blunt
LegislationARA Recognizes Blunt, Heitkamp For Legislative Efforts …
February 17, 2017
Agricultural industry continues to face federal regulatory challenges. Thankfully, agriculture’s allies in the U.S. Senate stepped forward. The Agricultural Retailers Read More
LegislationThe Fertilizer Institute Commends Senate On Confirmatio…
February 17, 2017
The Fertilizer Institute (TFI) President Chris Jahn issued the following statement on the Senate confirmation of Oklahoma Attorney General Scott Read More
Trump, Senate, Cabinet
LegislationBREAKING: Trump EPA Nominee Scott Pruitt Confirmed by S…
February 17, 2017
Scott Pruitt, who as Oklahoma’s attorney general spent years suing the Environmental Protection Agency over its efforts to regulate various Read More
ManagementFebruary Road Trip Edition
February 17, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss their recent visits to Indiana and Kentucky. Read More
Heritage Cooperative Finished Building Aerial
ManagementHeritage Cooperative, Agland Co-op Approve Merger
February 17, 2017
Agland Co-op and Heritage Cooperative stockholders have both approved the merger agreement between Agland Co-op and Heritage Cooperative. Now begins Read More
LegislationARA Fly-In: Ag Retail Descends on Capitol Hill, Lawmake…
February 15, 2017
More than 100 agricultural retailers, distributors and suppliers headed to Capitol Hill Tuesday morning for the Agribusiness Congressional Fly-in, according to a Read More
Untreated soybean seed Heartland Coop
Seed/BiotechMarrone Bio Innovations, Groundwork BioAg Bio-stacked M…
February 13, 2017
Marrone Bio Innovations, Inc. and Groundwork BioAg, Ltd have announced successful seed treatment field trials of the world’s first all-biological Read More