Timing Fungicide Sprays In Corn

LEXINGTON, KY.

   Application of strobilurin fungicides to foliage has been shown to improve agronomic performance in some situations. Yield increases and other agronomic benefits may result from disease control and/or from physiological effects induced by the active ingredient.

   Regarding fungicides, the first question a producer decides is whether or not to apply a product. If s/he decides to apply one, then the next question is, “When do I apply it?”

   In university tests over several years, it is common to see much more benefit to application made at VT-R2, then early in the season. See results from last year (Fig. 1), as an example. Last year’s results also show no economic benefit to two applications vs. one, which again is pretty typical of university results generally. There may be exceptions to these trends, but that is what they are: exceptions to the more general trends.

   I have also heard of fields receiving three and four applications of strobilurin fungicides in commercial fields (not necessarily in Kentucky). Since two applications do not consistently provide measurable benefit over and above that provided by one application, I am curious whether multiple applications really are beneficial. Plus, strobilurin products have label restrictions on the number of permissible sequential applications without using a fungicidal product not in Group 11.

   Bottom line: If using a corn fungicide, university research continues to highlight that one application made at VT/R1 is the optimal use. Δ

    DR. PAUL VINCELLI: Extension Plant Pathologist, University of Kentucky