Compatibility of biological control agents in the Agaricus bisporus production system

Abstract: Understanding ecological interactions among cohabiting microorganisms after their
introduction in the mushroom cultivation cycle is essential for improving both the quantity and quality of products. In addition, pest and disease management using biological control agents (BCAs) is compatible with organic agriculture and represents an environmentally safe
alternative that can reduce the use of chemical pesticides. As of late, compost green mould,
caused by Trichoderma aggressivum, has become a major fungal disease of button mushrooms. Relationships (synergistic/antagonistic/additive) between the following BCAs: bacterium Bacillus amyloliquefaciens B-241, actinobacterium Streptomyces flavovirens A06, and a commercial population of entomopathogenic nematode Steinernema feltiae in the control of T. aggressivum were evaluated in vivo. Their impact on mushroom yield was also assessed. The synergy factor (SF) was calculated as a ratio between the observed and expected impact on yield or the efficacy in pathogen suppression. The experiment was conducted under conditions of artificial inoculation with T. aggressivum after co-inoculation of these microorganisms. Satisfactory control of T. aggressivum was achieved by all tested microorganisms. The study revealed an additive interaction after simultaneous application of the bacterium B. amyloliquefaciens B-241 and actinobacterium S. flavovirens A06 in their efficacy against the pathogen. Similarly, additive relationships in efficacy against T. aggressivum were confirmed between the EPN population and each of the strains of the beneficial bacterium or actinobacterium. Regarding the impact on yield, synergistic interaction was detected between the two microorganisms, as well as between each beneficial microorganism and EPN S. feltiae. Since the results revealed compatibility among the tested BCAs in the mushroom cropping cycle, their synchronous application is recommendable.