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Poster: Biology & Disease Mgmt: Biological Control


Seasonal dynamics of fungal communities in pistachio and almond in California: implications for aflatoxin biocontrol management
A. ORTEGA-BELTRAN (1), R. Puckett (2), T. Michailides (3), D. Morgan (4), J. Moral (3) (1) UC Davis, U.S.A.; (2) UC Davis -KARE, U.S.A.; (3) UC Davis, U.S.A.; (4) UC Davis -KARE, U.S.A.

Interactions between pathogenic and nonpathogenic fungal species in the tree canopy are complex and can determine if disease will manifest in the plant and in other organisms such as honey bees. Seasonal dynamics of fungi were studied in almond and pistachio in California. In an almond orchard, experimental release of the atoxigenic biopesticide Aspergillus flavus AF36 to displace toxigenic strains has been conducted for five years. Because A. flavus is a pathogen of honey bees, our emphasis was on the presence of A. flavus in the flowers and the honey bees that attend them. Fungal species most commonly recovered from developing pistachio fruits were: Cladosporium herbarum, Alternaria alternata, Penicillium spp., Botrytis cinerea, Aspergillus niger, A. flavus, and yeasts. The main seasonal changes were detected in P. expansum and A. niger, which markedly increased from April to September. Conversely, the B. cinerea population significantly decreased during this period. In the almond, the dominant genera were: Cladosporium, Aureobasidium, Alternaria, Aspergillus, and Fusarium. Surprisingly, the diversity index was greater in the summer for both crops. The incidence of almond flowers with A. flavus ranged from 0 to 4.5%, depending on the year of study, and the incidence of honey bees carrying A. flavus ranged from 6.5 to 10%. This study helps the understanding of seasonal dynamics of pathogenic and nonpathogenic fungi and the impact of AF36 to pollinator honey bees.