Even with some rain in the forecast, the dry to drought conditions in Tennessee have reduced disease development and hence reduced the potential to break even on a fungicide in corn.
As corn begins to tassel, questions are rising about fungicide application. In corn, there has always been a lower probability of a return on fungicide investment. And this is even lower when you have environmental conditions that reduce disease, such as the dry-drought conditions of 2022. The majority of university research has shown fungicide are most profitable when disease is present and specifically from the summary that the Corn Disease Working Group, when disease is greater than 5% at R5, the average yield response from a fungicide was 9.6 bu/a. Whereas, the average yield response was only 1.5 bu/a when disease severity was less than 1%. Low disease severity is definitely the case this year in Tennessee corn and else where in the Mid-South and hence a fungicide is not going to be beneficial.
While there are some physiological benefits that have been attributed to fungicides, such as reduced stomatal conductance and improved water efficiency, this results are not consistence enough to have confidence that applying a fungicide in drought situations will be profitable in corn. While there is on-going research at University of Tennessee to further investigate such scenarios, no data is available at this time. Dr. Alison Robertson’s blog article from this time last year, summarizes some data very succinctly from the Iowa Soybean Association On-Farm Network, Pioneer on-farm trials, and her own programs research plots – looking back at other dry years (2012 and 2020), with very little disease. Where 0.5 to 0.8 bu/a yield response was recorded. And in summary states, “there are few data that suggest an application of a fungicide to drought-stressed crops would be a profitable practice.” Areas that have received rainfall, should scout for disease and make decisions based on disease presence and forecasted weather for further disease development and as always consult fungicide efficacy table (at https://utcrops.com/corn/disease/) to best align your fungicide product with the disease you are trying to manage.