Foliar Fungicide Management for Soybeans
There is no doubt that foliar diseases can and do cause significant soybean yield losses in the Midsouth. There is also no doubt that using foliar fungicides to manage or control some of these diseases has become an important input component for soybean production. However, the blanket use of these products should now be evaluated differently because of two important occurrences.
First, resistance to fungicides is confirmed in several fungal pathogens, most notably the resistance of the frogeye leaf spot pathogen, Cercospora sojina, to the strobilurins (FRAC Code/Group 11). This has likely resulted from the overuse of these products, to include their application in situations where the target disease was not at a yield-limiting level or the application was made under the assumption that a “plant health” benefit would be gained.
Second, results from a USB-sponsored multi-year, multi-state research project show that this blanket use of these fungicides will only occasionally result in a positive return on investment. The authors concluded that yield protection, not yield enhancement, should be the goal when using products to manage foliar diseases in soybean. As stated in a previous blog that summarized the results from this project, “foliar fungicides should be applied to soybeans in a high-yield environment when diseases are present at yield-limiting levels. Using these products on a regular basis as a yield enhancer is not economically feasible, and will hasten resistance development in fungal pathogens”. Also, some prominent foliar diseases are not controlled by foliar fungicide. Click here for a detailed discussion about using fungicides for managing soybean diseases, and here for a detailed discussion about fungicide resistance management.
A May 2016 PMN webinar entitled “Integrated Approaches to Fungicide Applications in Soybean“ by Dr. Hillary L. Mehl of Virginia Tech Univ. presents valuable and useful information that will help growers and practitioners understand best management practices for foliar fungicide use in soybean. Of special importance is her coverage of the when’s and how’s of scouting for foliar diseases. This webinar is open-access through July 31, 2016.