Integrating biocontrol agents in strawberry powdery mildew control strategies in high tunnel growing systems

Strawberry powdery mildew is a serious disease and its control is based on chemical fungicides. The efficacy of alternatives to chemical fungicides was evaluated and their integration into strategies against strawberry powdery mildew to reduce pesticide residues on fruits was also tested. Bicarbonates and mineral oils were poorly effective. Biocontrol agents (BCAs), like Ampelomyces quisqualis, Bacillus subtilis and Trichoderma harzianum T39, controlled the disease, but to a lesser extent than chemical fungicides. When BCAs were alternated with chemicals, a significant reduction of chemical fungicide residues was achieved while maintaining good powdery mildew control. None of the tested strategies increased populations of the pest Tetranychus urticae, nor had side effects on the beneficial predatory mite Amblyseius andersoni populations and, consequently, they can be regarded as safe for the ecological balance of arthropods in strawberry greenhouses.