Type of Document Dissertation Author Eckhardt, Lori G Author's Email Address email@example.com URN etd-0707103-152855 Title Biology and Ecology of Leptographium Species and Their Vectors as Components of Loblolly Pine Decline Degree Doctor of Philosophy (Ph.D.) Department Plant Pathology & Crop Physiology Advisory Committee
Advisor Name Title John P. Jones Committee Chair Kier Klepzig Committee Member Marc A. Cohn Committee Member Richard A. Goyer Committee Member Rodrigo A. Valverde Committee Member Walton R. Smith Dean's Representative Keywords
- loblolly decline
- insect vectors
- spatial analysis
Date of Defense 2003-05-02 Availability unrestricted AbstractLoblolly pine (Pinus taeda L.) decline (LPD) has been present in upland sites of central Alabama since the 1960s. Symptoms of LPD (fine root deterioration, short chlorotic needles, sparse crowns, reduced radial growth) begin in the 30-40 yr age class, resulting in premature death at ages 35-50. Previously, declining loblolly was diagnosed as littleleaf disease (LLD); however, site conditions associated with LPD are different from LLD sites. Littleleaf disease only occurs on eroded, heavy clay soils and is secondarily associated with the fungus, Phytophthora cinnamomi. In contrast, LPD occurs on sandy, well-drained soils and is associated with Leptographium spp., as well as with root-feeding bark beetles and weevils.
In the present study, 17 species (eleven newly reported) of subcortical root- and lower-stem feeding beetles were identified as vectors of Leptographium species, of which Hylastes salebrosus, H. tenuis, Hylobius pales and Pachylobius picivorus were statistically more abundant (F3,14=13.90, p=0.003) in LPD sites. Leptographium terebrantis, L. procerum, L. lundbergii, and L. serpens were isolated from the roots and insects. Pathogenicity studies suggested that L. lundbergii and L. serpens, fungi not previously reported in the U.S., were more virulent on loblolly pine.
Spatial analysis correlated LPD to site and stand physical factors. Slope and aspect were the predominant predictive variables of LPD in central Alabama. Convexity and elevation were predictive only in combination with other topographical factors. These analyses have allowed the creation of LPD risk maps to accurately predict areas of loblolly decline, providing a vital new tool for managing southern forests for predetermined purposes.
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