Fungicides are important tools for preventing and managing plant disease. Unlike insecticides and some herbicides which kill established insects or weeds, fungicides are most commonly applied to protect healthy plants before infection occurs. Resistance to fungicides is one of many possible causes of poor disease control (see Is Resistance to Blame?). Resistance refers to a situation where a given fungicide once controlled a particular fungal population but, after one or more applications, that fungicide no longer controls that population. To understand the process of selection that leads to fungicide resistance see Understanding Resistance. This module describes how fungicides work, the factors that contribute to fungicide resistance, and how resistance can be delayed or managed.
This module was expertly reviewed by:
Dr. Turner Sutton, Professor Emeritus, Department of Plant Pathology, NC State University, and,
Dr. Allison Talley, Syngenta Crop Protection
Topics Included in this Module
- Fungicide Terms to Know — Understand the terms that describe fungicide activity and resistance development
- Is Fungicide Resistance to Blame? — Most fungicide failures are not likely due to resistance.
- Mechanisms of Fungicide Resistance — There are several ways that populations of fungi become resistant.
- Raised Resistance Risks — The fungicide mode of action can determine the likelihood and speed of resistance development
- Proactive Fungicide Resistance Avoidance — Use diverse disease control tactics to help avoid resistance.
- Spraying by the Numbers — Fungicides with similar modes of action could exhibit cross resistance. One way to avoid this is by rotating chemically dissimilar fungicides.
- How to Manage Fungicide Resistance — If fungicide resistance is confirmed or highly suspected, diverse approaches to managing resistance need to be incorporated
- Resources and Suggested Reading
Compiled by Dr. Wayne Buhler