EPA Releases Guidance on Slowing Pest Resistance

November 14, 2017

The U.S. Environmental Protection Agency (EPA) recently released two pesticide registration notices (PRNs) that impact how technology providers, crop advisers, and producers manage resistance. These documents are in addition to a new framework to address Bt resistance in corn rootworm released in 2016. These releases, which all went through public comment, provide guidance in managing resistance and support the strategies and goals of the Iowa Pest Resistance Management Program (IPRMP).

PRN 2017-1, Guidance for Pesticide Registrants on Pesticide Resistance Management Labeling, improves information on pesticide labels to help pesticide users minimize and manage pest resistance.  PRN 2017-1 details recommended placement and format of mode of action (MOA) codes used by the Weed Science Society of America (WSSA), Fungicide Resistance Action Committee (FRAC), and Insecticide Resistance Action Committee (IRAC) for herbicides fungicide, and insecticide labels, respectively. PRN 2017-1 recommends that resistance-management statements be included in the Directions for Use section on labels under the heading “Resistance-Management Recommendations” and provide references to resources for guidance on resistance management. Resistance-management statements could include recommendations to scout follow herbicide application, rotate herbicide modes of action, and tank-mix herbicides with different modes of action.

PRN 2017-2, Guidance for Herbicide-Resistance Management, Labeling, Education, Training, and Stewardship, lays out EPA’s approach to support strategies to slow the development of herbicide resistance and prolong the useful life of herbicides. The guidance is being implemented for new and existing herbicides under the registration or registration review programs, respectively. Similar to the stated goals of the IPRMP, the notice observes that a “collaboration of growers, crop advisors, academia, Federal and State regulators, registrants and others” is important in “developing and implementing herbicide resistance management strategies.”

PRN 2017-2 recommends that labels should:

  • Clearly express all application parameters, such as maximum dose and number of applications per year.
  • Recommend, but not require, that fields be scouted before and after herbicide application.
  • Contain a statement that users should report lack of performance to the registrant, who is expected to investigate the report.
  • Contain a statement advising the user to seek information regarding resistant weed populations in the user’s region.

PRN 2017-2 reiterates the requirement that registrants must report any suspected resistant weed populations to EPA, and also provides recommendations for education, training, and stewardship. Educational materials should include a resistance-management plan as well as a remedial-action plan in the event of suspected resistance.

In 2016, EPA released a new framework to delay corn rootworm resistance, Corn Rootworm Resistance Management and Framework for Bt Corn. Some of the specific measures spelled out in the framework include:

  • Each Bt technology provider must develop and implement an education outreach program consistent with good IPM practices. Practices required to be part of the program include:
    • Rotation to an alternate non-host crop
    • Planting of Bt corn containing multiple traits targeting corn rootworm
    • Rotating to an alternate Bt trait, if available
    • Planting of non-Bt rootworm protected corn with a soil-applied insecticide
  • Bt technology providers are required to investigate reports of unexpected damage to Bt corn fields and determine if corn rootworm is indeed resistant to Bt.
  • If resistance is confirmed, companies are required to notify affected parties in areas with resistant populations, impose restrictions on the use of Bt corn product with resistance in the affected area, and encourage growers to implement strategies to reduce the resistant populations, such as crop rotation to a non-host crop.

The release of these updates demonstrate the level of concern EPA has regarding the development of pest resistance. It should be noted that the recommendations presented in these PRNs aren’t novel, but support established resistance management practices. While only recommendations at this point, practices promoted by the EPA should be considered areas of emphasis and may indicate future directions for regulatory oversight. Voluntary adoption of recommended practices in the IPRMP will not only help preserve the useful life of pest management technologies, in the context of local crop production systems, but help preclude the necessity of additional regulation oversight.

PRN 2017-1, Guidance for Pesticide Registrants on Pesticide Resistance Management Labeling

PRN 2017-2, Guidance for Herbicide-Resistance Management, Labeling, Education, Training, and Stewardship

Corn Rootworm Resistance Management and Framework for Bt Corn


Evan Sivesind, Department of Entomology, 515-294-7990, sivesind@iastate.edu