Most weed control failures are not due to resistance. Before assuming weeds surviving an herbicide application are resistant, eliminate other possible causes of poor control:
- Herbicide application
- Inadequate rate
- Poor spray coverage and/or incorporation
- Improper timing of application of postemergence herbicides (after weeds are too large to control)
- Failure to use an adjuvant (if needed)
- Excessive dust with post-emergence applications
- Spray intercepted at application by wheel traffic
- Antagonism between two or more herbicides
- Soil and/or climatic conditions
- Excessively wet or dry soil
- Seedbed condition (clods, etc.)
- Herbicide adsorption to soil particles or organic matter
- Stress conditions, such as hot and dry
- Lack of timely rainfall for activation
- Wash-off of post-emergence herbicides
Compiled by Dr. Wayne Buhler, PhD.
Topics Included in this Module
- Introduction to Herbicide Resistance
- Herbicide Resistance Terms to Know — Understand the difference between population shift and resistance as well as other concepts.
- Is Herbicide Resistance to Blame? — Resistance is not the only cause of weed control failure
- Incidence and History of Herbicide Resistance — Resistance to one or more of 25 herbicide families has been observed in the U.S.
- Mechanisms of Herbicide Resistance— How does resistance develop in a population?
- Proactive Herbicide Resistance Management — Methods to help slow or prevent the development of herbicide resistance.
- How to Manage Herbicide Resistance — What you can do if resistance is already a problem
- Herbicide Spraying by the Numbers — Use information on pesticide labels to rotate herbicide “families”
- Resources and Suggested Reading — Additional information about herbicide resistance.
- Resistance Lessons — Resistance lessons provided courtesy of the Weed Science Society of America