Developing biopesticide-based programmes for managing powdery mildew in protected strawberries in the UK

Abstract

Powdery mildew, caused by Podosphaera aphanis, is an important disease of strawberries and currently its control in the UK is very dependent on conventional fungicides. A series of experiments were carried out to integrate conventional fungicides with biopesticides and biostimulants for mildew control. In 2015–2016, the biopesticides Sonata (Bacillus pumilis) and AQ10 (Ampelomyces quisqualis) achieved at least as good as or better mildew control where they were applied alone rather than alternated with or tanked mixed with conventional fungicides. Three mildew management programmes were evaluated in 2017 on an ever-bearer cultivar. In the B. pumilis based programme, the need for treatment and the choice of products were partially determined by predicted mildew risks. The incidence of mildew on leaves was very low in untreated plots with virtually no mildew observed in the other treated plots. By contrast, mildew on the fruit rose rapidly from 2 % in late July to >90 % in late August in untreated plots. In treated plots, the percentage of fruit with mildew did not rise above 3 % with the three managed programmes based on B. pumilis. There were no significant differences in total yield and marketable yield between the managed programmes and the routine fungicide programme, but all were significantly greater than the untreated control. Most of the unmarketable fruit in the untreated control was due to infection with powdery mildew. The results suggested that strawberry powdery mildew can be effectively managed by the integrated use of biopesticides, biostimulants and conventional fungicides.