Biological control of yellow rust of wheat (Puccinia striiformis) with Serenade®ASO (Bacillus subtilis strain QST713)

Yellow rust (Puccinia striiformis f. sp. tritici) is an important disease in wheat causing significant yield reductions, if not effectively controlled. The biofungicide Bacillus subtilis strain QST 713 suspension concentrate (Serenade®ASO) was investigated for its potential for yellow rust control in winter wheat field trials. Serenade®ASO reduced severity of yellow rust significantly, providing up to 60% control at BBCH growth stage 65-69, under moderate disease pressure. Under high disease pressure reductions were more variable and provided less than 30% control. An increase in the number of applications of biofungicide from two to four per season tended to improve disease control, although differences were not always significant. With a few exceptions no clear dose-response was seen between using 1, 2, 4, 6 or 8 l/ha applied 4 times at 8-10-day intervals. Yield responses were positive, but responses to biofungicide were only significant in a few cases, and in all cases the level of control and yield responses were significantly lower compared with using prothioconazole as chemical control. An outdoor pot trial using artificial inoculation tested preventive and curative application of Serenade®ASO at three dose rates. This trial confirmed the lack of a clear dose response but showed that timing had a major impact on control, with the best control obtained at the day of inoculation. This study revealed that Serenade®ASO cannot stand alone in the control of yellow rust. More research is needed to develop integrated disease management strategies which also include biofungicides.