Evaluation of Beauveria bassiana for Management of Citrus Thrips (Thysanoptera: Thripidae) in California Blueberries

Citrus thrips, Scirtothrips citri (Moulton), is a plant-feeding pest most widely recognized for causing damage to citrus and mango fruits. This insect has broadened its host range to become a significant pest of commercial blueberries grown in the San Joaquin Valley of California. We evaluated Beauveria bassiana (Balsamo) for control of citrus thrips in blueberries grown under two watering regimes (drip irrigation with and without overhead sprinklers) and using two fungal formulations (commercially available spores in suspension vs. colonized seed) over two sampling periods, that is, for two 3-d periods after treatment. We found significant differences in thrips densities as a function of water regime treatment and fungal formulation. Thrips levels were reduced significantly with both fungal treatments at 3 d after treatment, but at 6 d, only results with colonized seed differed from the control treatment. These data suggest entomopathogenic fungi might be useful for control of citrus thrips on blueberries in particular situations (in organic production or as a resistance management tool) but that traditional pesticides will likely remain the preferred management option.