There are several ways that populations of fungi can become resistant to fungicides, these include:
1. Altered target site. A fungicide has a specific target site where it acts to disrupt a particular biochemical process or function. If this target site is somewhat altered, the fungicide no longer binds to the site of action and is unable to exert its toxic effect. This is the most common mechanism that fungi use to become resistant. See example below.
(i) ![]() |
(ii) ![]() |
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2. ![]() [Fungal cell] |
3. ![]() [Fungal cell] |
![]() [Fungal cell] |
![]() Close-up of fungal hyphae; showing cell walls |
Compiled by Dr. Wayne Buhler, PhD.
Topics Included in this Module
- Fungicide Terms to Know — Understand the terms that describe fungicide activity and resistance development
- Is 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