The past several years have seen a lot of excitement — and debate — over the label for plant health benefits of strobilurin fungicides. Many farmers swear they’ve seen healthier plants and longer-lasting foliage after an R3 application of a strobilurin, even in the absence of disease.

University plant pathologists like Kiersten Wise at Purdue aren’t sold on the practice, though.

“What we’ve found is that when we don’t have disease pressure there — foliar diseases such as frogeye leaf spot or Cercospora leaf blight — we don’t often see an economic benefit from a fungicide application,” Wise says.

“One of the big drawbacks to using fungicides for these plant health benefits is that when we use the same mode of action over and over again, we select for fungicide-resistant strains of the fungus,” she adds, noting that frogeye leaf spot is of particular concern. “Our standard recommendation is that fungicides should be applied only when foliar disease pressure is potentially yield-limiting.”