Control of powdery mildew (Blumeria graminis spp.) in cereals by Serenade®ASO (Bacillus amyloliquefaciens (former subtilis) strain QST 713)

Powdery mildew (Blumeria graminis f.sp. tritici, f.sp. hordei, f.sp. avenae) is an important disease in cereal crops causing significant yield reductions, if not effectively controlled. The biofungicide Bacillus amyloliquefaciens (former subtilis) strain QST 713 suspension concentrate (Serenade (R) ASO) was investigated for its potential as a control agent against powdery mildew in winter wheat, spring barley, oats and triticale. Serenade (R) ASO reduced the severity of powdery mildew, providing moderate control in the range of 20-65%. The efficacy was highest at the earlier assessments and less pronounced at later assessments. With a few exceptions, no clear dose-response was seen between using 1, 2, 4, 6 or 8 L/ha Serenade (R) ASO applied four times at 8-10-day intervals. The efficacy was more variable compared with chemical references. Yield responses were positive following treatments. However, the yield increase by Serenade (R) ASO was insignificant and significantly inferior to that of prothioconazole. In a few cases, the use of Serenade (R) ASO in combination with the adjuvant Silwet (R) Gold improved the efficacy, but the results were inconsistent. The preventive and curative application of Serenade (R) ASO was tested at three dose rates in an artificially inoculated wheat and barley greenhouse pot trial. These trials confirmed the lack of a clear dose-response but confirmed that timing has a major impact on control, with the best control obtained when application took place on the day of inoculation in wheat and 0-2 days after inoculation in barley. This study revealed that powdery mildew challenges Serenade (R) ASO as a stand-alone control measure. The results show that further research is needed for the promotion of biofungicides as part of an integrated disease management approach in cereal diseases.