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
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
MicronutrientsMicronutrients Going Macro
September 9, 2014
Between 2014’s fantastic growing conditions and a heightened awareness on plant nutrition, the major players in micronutrients are gearing up for another big year. 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
FungicidesSudden Death Syndrome, Brown Stem Rot Reported In Indiana Soybeans
September 3, 2014
Farmers and retailers should be watching for symptoms of these two diseases over the next few weeks as they are best managed through preventative methods. Read More
Top 100 Articles
CropLife 100The Andersons Starts Venture Capital Subsidiary
January 26, 2015
The Andersons has established Maumee Ventures, a venture capital subsidiary designed to foster promising innovations that strategically align with the company’s core businesses. Read More
CropLife 100CHS Partners With Northern Partners Coop On Fertilizer Warehouse
January 21, 2015
In addition, the two companies will form a joint venture to build and operate a grain barge loading facility that will handle corn, soybeans and wheat for export through the CHS terminal at Myrtle Grove, LA. Read More
CropLife 100Wilbur-Ellis Move To Colorado Complete
January 20, 2015
Wilbur-Ellis Co. announces the opening of its new Agribusiness Division location in the Denver, CO, Metro Area. The new facility will host key personnel as the company shifts the base of its Agribusiness operations from California to Colorado. Read More
CropLife 100United Suppliers, McGregor Co., Five Others To Form Aligned Ag Distributors
January 20, 2015
These companies will continue to operate as independently owned and operated businesses, however, their crop protection divisions will now be formally aligned under the umbrella of Aligned Ag Distributors. Read More
CropLife 100Bozeman Named SEEDWAY Chief Operating Officer
January 16, 2015
He succeeds Donald Wertman, who will retire at the end of August 2015 after 40 years with the GROWMARK subsidiary. Read More
CropLife 100Wilbur-Ellis’ Craig Bair Honored For Safety Contributions To Ag Aviation
January 14, 2015
The William O. Marsh Safety Award recognizes significant achievements in safety, safety education or an outstanding operational safety program. Read More
Latest News
ManagementOABA Conference Set To Highlight Trends, Technology And…
January 29, 2015
The third annual Ohio AgriBusiness Association (OABA) Industry Conference is set to take place February 4-5. Read More
FertilizerThe Fertilizer Institute President Jahn Testifies Befor…
January 28, 2015
The committee hearing, "Freight Rail Transportation: Enhancing Safety, Efficiency, and Commerce," looked at challenges facing our nation's freight rail network created by higher demand, rules and regulations and infrastructure needs. Read More
HerbicidesPurdue University Acquires Technology For Herbicide Mol…
January 28, 2015
Protea's LAESI DP-1000 Instrument System will be used in Purdue's College of Agriculture, the Department of Botany and Plant Pathology, for the molecular imaging of herbicide active ingredients and other related compounds to optimize herbicide applications and improve weed management.  Read More
FertilizerH.J. Baker Hires New Crop Peformance Marketing Manager
January 27, 2015
As Marketing Manager for the Crop Performance division, Usman Khalid will work out of H.J. Baker’s global headquarters in Westport, CT, and will drive new initiatives for the division. Read More
CropLife 100The Andersons Starts Venture Capital Subsidiary
January 26, 2015
The Andersons has established Maumee Ventures, a venture capital subsidiary designed to foster promising innovations that strategically align with the company’s core businesses. Read More
Exclusive state-of-the art Stueve Construction designed “Vista View” Elevated Control Room.
Eric Sfiligoj2015 Agricultural Market Read: Mixed
January 26, 2015
The agricultural market could look radically different this year, profit-wise, depending upon which segment you do business in. Read More
Edward Chell Biosafe
Crop InputsBioSafe Systems Names Ed Chell California Territory Man…
January 26, 2015
BioSafe Systems has announced the recent addition of Ed Chell as California Territory Manager for the agrichemical division, supporting the crop protection, water treatment and food safety business segments. Read More
InsecticidesBayer CropScience Introduces Sivanto Insecticide
January 26, 2015
Sivanto precisely targets key damaging pests at multiple insect life stages to prevent damage to plants and help minimize the spread of diseases from insect carriers. Read More
ManagementRetail Collaboration, Communicating Agriculture’s Good …
January 23, 2015
Editors Paul Schrimpf and Eric Sfiligoj discuss the recent creation of Aligned Ag Distributors, and the US Farmers and Ranchers Read More
FertilizerOSU Expert: Toledo Water Crisis A Turning Point For Ohi…
January 23, 2015
The August 2014 water crisis in Toledo, OH, impacted Ohioans’ views of Lake Erie algae problems by increasing the attribution of blame of algae growth on agriculture. Read More
FertilizerH.J. Baker Launching TIGER XP
January 22, 2015
Tiger-Sul introduces this next generation sulphur-bentonite product with a proprietary activator – ensuring farmers have a well-balanced nutrient replacement program. Read More
Crop InputsH.J. Baker Expands China Sales Force
January 21, 2015
Global Agricultural firm H.J. Baker announced that sales veteran Shi Dongshen has joined their Shanghai office in China. This newest hire follows the recent opening of their Lianyungang Sulphur Bentonite Plant. Read More
CropLife 100CHS Partners With Northern Partners Coop On Fertilizer …
January 21, 2015
In addition, the two companies will form a joint venture to build and operate a grain barge loading facility that will handle corn, soybeans and wheat for export through the CHS terminal at Myrtle Grove, LA. Read More
Matt Hopkins5 Bold Predictions For Ag Retail In 2015
January 21, 2015
This past year was filled with ups and downs for the nation’s top ag retailers, but what will 2015 have in store? Read More
SoftwareDeere Launches App Center
January 20, 2015
The John Deere App Center provides users the ability to search and find apps most useful to their business or operations. Read More
Crop InputsNew Syngenta Herbicide Approved In Soybeans, Sunflowers
January 20, 2015
Syngenta will sell BroadAxe XC herbicide in 2015 for use on soybeans, sunflowers and dry peas Read More
CropLife 100Wilbur-Ellis Move To Colorado Complete
January 20, 2015
Wilbur-Ellis Co. announces the opening of its new Agribusiness Division location in the Denver, CO, Metro Area. The new facility will host key personnel as the company shifts the base of its Agribusiness operations from California to Colorado. Read More
Crop InputsNovozymes Sales Figures Up For 2014
January 20, 2015
Novozymes announces its sales growth in 2014 was in line with expectations as sales grew by 7% compared with 2013. Read More