When it comes to the length of disease protection, newer branded fungicides have an edge over generic ones, according to trials conducted by Iowa State University.

Newer branded fungicides protected corn from fungal diseases for about 35 days in ISU tests, says Alison Robertson, an ISU Extension plant pathologist. Meanwhile, generic fungicides have provided 21 days of fungal disease protection in ISU trials.

So why apply products with a shorter protection period? They’re less expensive. A branded product may cost $15 per acre, while a generic one may cost about $8 per acre, Robertson says.

Still, there’s a catch.

No fungicide — branded or generic — protects corn for the 60-day grain fill period from tasseling (VT) to R6 (black layer). That’s why Robertson advises farmers to aim fungicide applications from VT to R3 (kernel milk stage) to provide fungal disease protection during the most critical time of grain fill.

If disease surfaces around tasseling, applying a more expensive branded chemistry fends off fungal diseases for five weeks through the R4 (kernel dough) stage.

If disease pressure holds off until the R2 (brown silk/blister) stage, however, a less expensive generic can provide protection through R4, Robertson says. Fungicide application returns diminish greatly after the R4 stage, she adds.

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Farmers who opt for generic fungicides should use a product that has at least two modes of action or a mix of two products each with a different mode of action. “This reduces the chances of fungicide resistance developing,” Robertson says.