Field evaluation of fungal competitors of Fusarium culmorum and F. graminearum, causal agents of ear blight of winter wheat, for the control of mycotoxin production in grain.

Thirty-seven antagonists, from a collection of 113 pre-screened microorganisms, were tested in field experiments on winter wheat for their ability to control ear blight and production of mycotoxins, particularly deoxynivalenol (DON), in grain by Fusarium culmorum and F. graminearum. Ears were spray-inoculated during anthesis with spore suspensions, first of test fungi and then of the pathogen. Isolates of F. equiseti were the most effective treatments. A strain of F. equiseti (G9) decreased DON consistently on wheat inoculated with F. culmorum, compared with the control, often by more than 70%. It performed well under severe disease pressure (F. culmorum at 10(5) conidia mL(-1)) and similarly to a standard fungicide, tebuconazole. Percentages of diseased grains and amounts of DON corresponded well. Small quantities of nivalenol (NIV) occurred in grain samples after treatment with some F. equiseti strains. On wheat inoculated with F. graminearum, F. equisti G2 decreased the percentage diseased grains by 92% and DON by 94%. One strain of F. equiseti (G2) was found to produce small amounts of NIV in pure culture.