Fungicide Resistance: Rotate Modes of Action, Not Just Brand Names

A different brand name is not necessarily a different fungicide strategy. Two products may contain different active ingredients yet act at the same biochemical target. Repeated exposure selects pathogen populations that can survive that mode of action.

Build a stronger spray program

Find the FRAC code. Check the label for the mode-of-action group before choosing the next application.
Rotate effective groups. Move to a non-cross-resistant mode of action rather than another product with the same code.
Limit consecutive applications. Follow label and FRAC guidance for the crop, pathogen and fungicide group.
Use mixtures correctly. Each partner should be effective against the target at the applied rate. A weak partner does not protect the stronger one.
Reduce disease pressure. Resistant varieties, sanitation, crop rotation, canopy airflow, forecasting and timely scouting reduce reliance on fungicides.
Apply preventively when required. Many fungicides provide limited rescue activity after disease is established.

Watch for warning signs

Suspect resistance when a correctly selected and applied product loses performance against a confirmed target while comparable products from other groups still work. First rule out poor coverage, wrong timing, rain wash-off, water-quality problems and misdiagnosis.

Bottom line: rotate the biological target, not the logo on the container. Preserve useful fungicides before field performance declines.

Source: Fungicide Resistance Action Committee resistance-management guidance and current code lists.

Do you record FRAC codes in your spray records?

Featured photo: Chris Ensminger via Unsplash.