Yoshida, M., Nakajima, T, Tomimura, K., Suzuki, F., Arai, M., and Miyasaka, A. 2012. Effect of the timing of fungicide application on Fusarium head blight and mycotoxin contamination in wheat. Plant Dis. 96:845-851.Fungicide application to control Fusarium head blight (FHB) and accompanying mycotoxin contamination in wheat is generally performed at anthesis because wheat is most susceptible to FHB around this stage. In this study, we evaluated the effect of the timing of fungicide application on FHB and mycotoxin (deoxynivalenol and nivalenol) accumulation in wheat based on our previous finding that the late period of grain development (beyond 20 days after anthesis [DAA]) is important to determine the final toxin contamination level in wheat. Thiophanate-methyl fungicide was tested under artificial inoculation conditions in which moisture and inoculum spores were provided throughout the testing period. Eight treatments differing in application timing (anthesis, 10, 20, and 30 DAA) and in the number of applications (0 to 2) were tested for 2 years. The results indicated that fungicide application timing differentially affects FHB (disease) and mycotoxin concentration. Fungicide application at 20 DAA reduced mycotoxin concentration in matured grain without reducing FHB severity, whereas application at anthesis was crucial for reducing FHB. These results and our previous findings suggest that around 20 DAA (late milk stage) is a potentially critical timing for mycotoxin control in wheat.Fusarium head blight (FHB), a destructive disease of wheat (Triticum aestivum L.), barley, and other small-grain cereals, is caused by several Fusarium spp. (17,18,26,29). These pathogens infect spikes and reduce grain yield and quality. Moreover, Fusarium spp. that cause FHB produce trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV) and the estrogenic mycotoxin zearalenone. Such mycotoxins are toxic to humans and other animals. Contamination of wheat and barley by these mycotoxins has been reported worldwide (31,41,42).The Fusarium graminearum species complex (23)(24)(25)37,46)