If fungicide resistance is confirmed or highly suspected, diverse approaches to managing resistance need to be incorporated into disease management strategies immediately for the species in question.
It is best to stop using the fungicide in question and other fungicides with the same MOA. If the decision is made to continue using the fungicide, there are several options:
- Start with proactive disease control with a fungicide with a different MOA that is known to control the resistant pathogen.
- Use the fungicide only in tank mixtures or prepacks with one or more different MOAs that are known to control the resistant pathogen.
- Do both i. and ii.
Any of these options provides at least one additional MOA that will help to prevent further spread of the resistant pathogen.
- Avoid moving soil or plant parts to other fields and farms. Use a power washer or compressed air to help remove these potential sources of pathogen inoculum from any equipment used in the field. If any fields have a history of fungicide resistant fungi, use farm equipment in those fields last.
- Seek advice from the Cooperative Extension Service, your agricultural chemical dealer, crop advisor, and/or University Extension Plant Pathologist to assist in the long term planning of disease control in subsequent crops.
Resistance management strategies can differ for a specific combination of crop, disease, and geographical area. In addition to citing MOA group numbers for a rotation scheme (see Spraying by the Numbers), remember to always follow the resistance management recommendations printed on the product label. Labeling information will indicate how to reduce the potential development of resistant pests and the conditions under which product rotation to a different MOA is needed. Adhering to the resistance management principles outlined above will help prevent resistance from recurring and prove beneficial in managing resistance in the long term.
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