Impact of Fusarium graminearum inoculum availability and fungicide application timing on Fusarium head blight in wheat

Fusarium head blight (FHB) of wheat (caused by Fusarium graminearum Schwabe (telemorph Gibberella zeae (Schwein.) Petch) is considered one of the most economically important diseases on wheat in the United States. Currently, farmers rely heavily on fungicides applied at early anthesis or Feekes Growth Stage (FGS) 10.5.1 to protect their crop from this disease. Field trials were conducted at the Agronomy Center for Research and Education in West Lafayette, IN during the 2012-2013 and 2013-2014 growing seasons to determine the impact of post-anthesis fungicide timing in conjunction with initial infection by F. graminearum on development of FHB and deoxynivalenol (DON) in soft red winter wheat. To achieve this, each experimental plot within a treatment was inoculated and received a fungicide application on the same day beginning at FGS 10.5.1 (anthesis), and continuing each day for anthesis +1, 3, 5, 7, 9, and 11 days. The fungicide prothioconazole + tebuconazole was applied at 475 mL/ha, and experimental plots were inoculated with macroconidia of F. graminearum on the same day as each fungicide application. Results indicate that fungicide applications made up to 11 days post-anthesis may be useful in reducing FHB and DON in wheat when inoculum becomes present near the time of application.