Type of Document Master's Thesis Author Johnson, Crawford Wood Author's Email Address email@example.com URN etd-12122003-141334 Title The Performance of the Baldcypress Leafroller (Archips goyerana Kruse, Lepidoptera:Tortricidae) in Response to Fertilization, Thinning, and Genetic Variation in Host Baldcypress (Taxodium distichum L. Richard) Degree Master of Science (M.S.) Department Entomology Advisory Committee
Advisor Name Title Richard Goyer Committee Chair Michael Stout Committee Member Seth Johnson Committee Member Keywords
- insect fecundity
- insect response to nitrogen
- river diversions
- insect resistance
- saltwater intrusion
- growth and differentiation hypothesis
Date of Defense 2003-12-01 Availability unrestricted AbstractMississippi River diversions into coastal Louisiana wetlands aim to provide nutrient inputs and slow the impacts resulting from saltwater intrusion. Baldcypress (Taxodium distichum L. Richard) exhibits significant intraspecific tolerance to salinity and is being developed for restoration projects. Two studies were conducted using five half-sibling families of baldcypress planted at two locations in southeast Louisiana to investigate the effects of nutrient additions, thinning, and phenology on the growth of the baldcypress leafroller (Archips goyerana Kruse, BCLR). In the Jeanfreau study, families were subjected to a control, low, and high level of fertilization simulating two-four years’ effects, respectively, from a Mississippi River diversion. In the Delacroix study, an area impacted by a river diversion, these same families were subjected to control and thinned treatments.
BCLR larval bioassays were conducted in the laboratory to ascertain relative growth rate (RGR), development time, and pupal weights, a surrogate for potential fecundity. Tree growth and foliage nutrients, phenolics (Jeanfreau only), moisture, length and width were measured.
Fertilization did not consistently influence tree growth. Dry pupal weights and relative growth rates in most families were greater, and development times shorter, each year in the low fertilization treatment. Phenology differences among families were consistent across fertilization treatments and significantly affected BCLR growth. Pupal weights were lower on early-leafing families due to the decreasing suitability of the foliage at time of larval emergence. Thinning did not have a clear effect on BCLR development during the time of study. Phenological effects on larval growth and foliar nutrient samples were experimentally removed by allowing the foliage among families to reach comparable stages of growth in 2003. Females reared on family cb3 in the thinned treatment exhibited significantly heavier pupae than the control, implying a potentially greater fecundity, but foliage analyses revealed total nutrients and moisture content were less concentrated in the thinned treatment. There were no other significant differences in larval performance.
Overall, this evidence suggests a more nutritious food resulting from limited fertilization inputs may lead to a BCLR population increase. Larval growth and performance may not be affected immediately by thinning. Phenological variation in budburst among families was found to be a significant factor affecting leafroller performance.
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