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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED WEED MANAGEMENT SYSTEMS FOR ORGANIC AND CONVENTIONAL CROPS OF THE SOUTHEASTERN COASTAL PLAIN

Location: Crop Protection and Management Research

Title: Reducing the risks of herbicide resistance: best management practices and recommendations

Authors
item Norsworthy, J -
item Ward, S -
item Shaw, D -
item Llewellyn, R -
item Nichols, R -
item WEBSTER, THEODORE
item Bradley, K -
item Frisvold, G -
item Powles, S -
item Burgos, N -
item Witt, W -
item Barrett, M -

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2012
Publication Date: August 1, 2012
Citation: Norsworthy, J.K., Ward, S., Shaw, D., Llewellyn, R., Nichols, R.L., Webster, T.M., Bradley, K., Frisvold, G., Powles, S., Burgos, N., Witt, W., Barrett, M. 2012. Reducing the risks of herbicide resistance: best management practices and recommendations. Weed Science. Special Issue:31-62.

Interpretive Summary: Herbicides are the foundation of weed control in commercial crop production. However, herbicide-resistant weed populations are developing rapidly in response to herbicide use patterns. In order to hasten the development of herbicide resistant weeds, critical practices include reducing selection through diversification of weed control techniques, minimizing spread of resistance genes and genotypes, and eliminating additions of weed seed to the soil. The long-term economic benefits of avoiding additional costs associated with managing herbicide resistance weeds are clear. Nevertheless, widespread adoption of these best management practices must overcome several real barriers, in particular growers’ focus on immediate economic returns, which when combined with the belief that evolution of herbicide resistance in weeds is unavoidable and that continued availability of novel herbicide technologies will solve the problem. Two key recommendations in particular must be more widely implemented: diversifying weed management practices and using multiple herbicide mechanisms of action. Growers need to be educated about herbicide mechanisms of action and made aware that discovery of new herbicide chemistries is rare, that the existing herbicide resource is exhaustible, and that indiscriminate herbicide use leading to rapid evolution of herbicide- resistant weeds may result in the loss of herbicide options for all.

Technical Abstract: Herbicides are the foundation of weed control in commercial crop production. However, herbicide-resistant weed populations are developing rapidly in response to selection pressure. Critical practices include reducing selection through diversification of weed control techniques, minimizing spread of resistance genes and genotypes, and eliminating additions of weed seed to the soil. Effective herbicide resistance management programs must consider all cultural, mechanical, and herbicide options available and employ the following best management practices: 1) Understand the biology of the weeds present. 2) Use a diversified approach to weed management focused on preventing weed seed production and reducing the number of weed seeds in the soil seedbank. 3) Plant into weed-free fields and then keep fields as weed free as possible. 4) Plant weed-free crop seed. 5) Scout fields routinely. 6) Use multiple herbicide mechanisms of action that are effective against the most troublesome or herbicide-resistance-prone weeds. 7) Apply the labeled herbicide rate at recommended weed sizes. 8) Emphasize cultural practices that suppress weeds by utilizing crop competitiveness. 9) Use mechanical and biological management practices where appropriate. 10) Prevent field-to-field and within-field movement of weed seed or vegetative propagules. 11) Manage weed seed at harvest and post-harvest to minimize the weed seedbank. 12) Manage weeds on field border to minimize this area as a source of propagules.

Last Modified: 7/28/2014