Endophytic colonization and pest management potential of Beauveria bassiana in strawberries

BACKGROUND: Chemical pesticides are predominantly used for managing various pests on strawberries in California. Biological control is limited to the release of predatory mites against spider mites. Predominant use of chemical pesticides does not provide complete and satisfactory control of certain pests and interferes with biological control. Microbial control is an unexplored area in California strawberries. Limited pest control with current practices, risk of pesticide resistance, and concern for environmental safety associated with excessive use of chemical pesticides prompt the search for safer and effective alternatives. Entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin and a botanical pesticide, azadirachtin are active against most of the strawberry pests. Additionally, B. bassiana is known to endophytically colonize some plant species and provide protection against herbivore damage. Identifying non-chemical alternatives is a critical area in strawberry pest management. OBJECTIVE: Explore the potential of B. bassiana against strawberry pests and the ability to colonize strawberry plants. METHODS: Efficacy of reduced rates of chemical pesticides, B. bassiana, and azadirachtin against adult lygus bug, Lygus hesperus Knight were determined in laboratory assays. Greenhouse and laboratory studies were conducted to determine endophytic colonization potential of B. bassiana in strawberry plants. Efficacy of B. bassiana against L. hesperus was determined in small plot field trial in strawberries and against other pests in greenhouse strawberries was also studied. RESULTS: Certain combinations of chemical pesticides and B. bassiana at reduced rates improved L. hesperus mortality. Beauveria bassiana colonized and persisted in various strawberry tissues for up to 9 weeks after inoculation. No impact of the B. bassiana on L. hesperus numbers was seen in the field study, but was found effective, along with azadirachtin, against some pests in the greenhouse study. CONCLUSION: Non-chemical alternatives such as B. bassiana and azadirachtin have a good potential for strawberry pest management.