Management of insect pests of crapemyrtle (Lagerstroemia spp) with special reference to the ecology and biology of Altica litigata Fall (Coleoptera: Chrysomelidae)
Pettis, Gretchen Van De Mark
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Japanese beetles (Popillia japonica Newman) and crapemyrtle aphids (Tinocallis kahawaluokalani Kirkaldy) are the two primary insect pests of crapemyrtle. The flea beetle Altica litigata Fall (Coleoptera: Chrysomelidae) has become an important economic pest of container-grown crapemyrtle (Lagerstroemia spp.) in southeastern United States nurseries in the past decade. Until now, chemical management has been the primary control strategy used by commercial crapemyrtle producers. Ecological and biological information is needed to establish integrated management options for these three economically important pests and particularly for the emergent beetle pest, A. litigata. Identification of pest-resistant crapemyrtle cultivars provides a foundational and immediate pest management strategy. Field and lab, choice and no-choice, multi-state and multi-year feeding trials with Japanese beetle and A. litigata revealed a spectrum of resistance present in the crapemyrtle genome. Cultivars with L. faurei parentage were less preferred than L. faurei x L. indica crosses. Elucidating the mechanisms that impart pest-resistance to currently available Lagerstroemia spp. cultivars provides additional tools for future plant improvement efforts for academic and commercial interests. Leaf color, nutrient content and toughness of were evaluated for correlations with beetle feeding preference. No significant relationships emerged between feeding damage and the leaf characteristics measured. Finally, a better understanding of the basic phenology of A. litigata allows for more precise targeting of pest management efforts. Degree day models revealed that, when averaged among the six host plants examined, larval and pupal development orequired 237.3 degree-days (DD) above a threshold of 9.2 C. Eggs required 87.5 DD oabove a 9.8 C threshold. Altica litigata developed most rapidly on Oenothera spp. and most slowly on Gaura spp. Temperature had a significant positive correlation with development and there were significant temperature by host plant interactions. Overall, the series of basic and applied studies presented in this dissertation permits the development of a holistic management plan for two established and one emerging pest of an important woody ornamental crop by incorporating the foundations of an Integrated Pest Management (IPM) program.