Evaluation of selected microbial strains and commercial alternative products as seed treatments for the control of Tilletia tritici, Fusarium culmorum, Drechslera graminea and D. teres.
The aim of this study was to further characterize the activity as seed treatments of five actinomycete and four Trichoderma strains that in a previous screening under controlled conditions had shown promising activity against Tilletia tritici. The strains were evaluated under controlled conditions for activity against Fusarium culmorum and Fusarium spp./Septoria nodorum [Leptosphaeria nodorum] on wheat, and against Drechslera graminea and D. teres [Pyrenophora teres] on barley, and some of them were tested for control of T. tritici in the field. Eleven microbial and four non-microbial, commercially available alternative products, most of them developed and marketed for other uses than seed treatment, were also included in the study, mainly to determine their activity against T. tritici. In the experiments under controlled conditions, the strains of Trichoderma failed to reduce seedling infection by the pathogens stated above, and the two strains tested against T. tritici in the field did not protect against bunt. These results indicate that the tested Trichoderma strains are not candidates for further development. None of the actinomycetes reduced net blotch (D. teres), but the strains FZB 53 and W 490 had a significant reducing effect on barley leaf stripe (D. graminea) and seedling blight of wheat caused by F. culmorum and, in case of FZB 53, also on Fusarium spp./S. nodorum. In a year with conditions favouring the development of bunt, FZB 53 and W 490 had also activity against T. tritici in the field. For FZB 53, it could be shown that the level of bunt control depended on resistance of the respective variety, but overall the activity of FZB 53 against bunt was insufficient in that year. Of the commercial B. subtilis products evaluated against T. tritici, FZB 24 and Serenade showed activity under controlled conditions, but not in the field. FZB 24 and Serenade had also some activity against D. teres but not against F. culmorum. Serenade was also effective against D. graminea. In two replicated field experiments, the highest level of bunt control (82 and 94% efficacy) was obtained with the seed treatment product Tillecur. In four experiments under controlled conditions, Tillecur showed also consistent activity (mean: 78% efficacy) against barley leaf stripe. Results obtained with all other commercial products either gave no indication for T. tritici activity at the rates tested, or bunt control in the field was low or inconsistent.