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Abstract
Flower thrips (Frankliniella tritici Fitch) is a key pest in southeastern U.S. blueberry production systems, particularly during the flowering period when injury to floral tissues significantly reduces fruit set, yield, and quality. This dissertation examines the ecology, spatial dynamics, seasonal biology, host associations, injury potential, and management strategies of F. tritici in both rabbiteye and southern highbush blueberry. The overarching goal was to develop a foundation for more sustainable, data-driven integrated pest management (IPM) practices.Field studies conducted from 2022 to 2024 revealed that F. tritici dominated thrips populations, accounting for over 95% of all individuals collected. Populations were generally higher in rabbiteye cultivars and were significantly influenced by temperature, flowering
phenology, and proximity to wild habitats. Spatial analyses showed non-random distributions and identified persistent hot spots within fields. Overwintering studies using emergence traps and alternate host sampling revealed that thrips primarily overwinter within blueberry fields and utilize surrounding weed species such as Raphanus raphanistrum, Rubus trivialis, and Lyonia lucida as reproductive hosts in late winter.
Greenhouse experiments quantified the effects of F. tritici injury on four cultivars under controlled conditions. Increasing thrips densities led to higher levels of flower injury, flower drop, and fruit deformation. Significant reductions in fruit weight and size were observed, especially in the southern highbush cultivar ‘Suziblue’ and the rabbiteye cultivar ‘Climax’. Injury thresholds and regression models using thrips-days were developed to predict yield loss more accurately.
Insecticide efficacy trials evaluated five conventional insecticides and one biopesticide over two seasons. Acetamiprid, spinetoram, and spinosad provided consistent suppression of both adult and larval thrips, while flupyradifurone and GS-omega/kappa-Hxtx-Hv1a had limited effectiveness. Two-spray programs offered better control but raised concerns over pollinator safety.
Together, these studies contribute a comprehensive understanding of F. tritici biology, injury dynamics, and management. This dissertation provides a science-based framework for developing integrated pest management (IPM) programs that balance pest suppression with pollinator and environmental conservation, supporting sustainable blueberry production in the southeastern United States.