Browsing by Author "David, Paul Joseph"

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    Bionomics of Platynota flavedana Clemens and P. idaeusalis (Walker)(Lepidoptera: Tortricidae) in Virginia apple orchards
    David, Paul Joseph (Virginia Polytechnic Institute and State University, 1985)
    The effects of pheromone trap placement on male moth catches of both species were studied. For P. flavedana, traps hung at 2.1 and 3.0 meters captured the greatest number of moths. Trap heights of 1.2, 2.1, and 3.0 meters caught the greatest number of P. idaeusalis moths. The outside-the-canopy trap position captured more P. flavedana moths, while the within-canopy trap location caught the greatest number of P. idaeusalis moths. Traps placed in the west portion of the tree captured the greatest number of P. flavedana moths. P. idaeusalis moth catches were not influenced by compass quadrants. Trap design and pheromone dispenser and rate influenced trap catches of P. flavedana. Development of P. flavedana and P. idaeusalis on a meridic diet was observed at constant temperatures in the laboratory. Lower developmental threshold values for egg, larval, and pupal stages of P. flavedana were: 10.6, 8.6, 9.0°C, respectively. Lower developmental threshold values of 9.7, 7.0, and 8.5°C were estimated for P. idaeusalis egg, larval, and pupal stages, respectively. An average of 101.5 °D10.6’, 379.6 °D8.6’, and 126.0 °D9.0’ were required for development of egg, larval, and pupal stages of P. flavedana, respectively. P. idaeusalis required 104.7 °D9.7’, 442.7 °D7.0’, and 132.2 °D8.5’ to complete development in the egg, larval, and pupal stages, respectively. Differences in rate of development were observed between food sources for both species. Within-tree spatial distribution of egg masses and fruit damage resulting from larval feeding for both species was investigated. P. flavedana egg masses were mostly found in the southern portion of the tree below 1.8 meters. Egg masses of P. idaeusalis were observed in greatest numbers in the southern and eastern quadrants of the tree below 2.8 meters. Fruit damage caused by larvae of both species was greatest in the lower portion of the tree. Wind dispersal of first-instar larvae between trees is believed to have influenced fruit damage distribution. The seasonal activity of P. flavedana and P. idaeusalis was monitored. Degree-day accumulations for first moth catch, first and peak egg deposition, and first and peak egg hatch of both generations are presented.
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    Ovicidal activity of methomyl on eggs of pest and beneficial insects and mites associated with apples in Virginia
    David, Paul Joseph (Virginia Polytechnic Institute and State University, 1982)
    Methomyl at seven concentrations, 0.051 to 0.204 kg ai/378.5 l water, was evaluated against eggs of pest and beneficial insects and mites associated with apples. The pest eggs studied were: Laspeyresia pomonella, Panonychus ulmi, Platynota spp., aphids, and Argyrotaenia velutinana. For A. velutinana, five rates of methomyl ranging from 0.013 to 0.204 kg ai/378.5 l water were used. Platynota spp., aphid, and A. velutinana eggs were highly susceptible to the material. P. ulmi eggs were not susceptible. Eggs of beneficial syrphid flies, Aphidoletes aphidimyza, Leptothrips mali, and Stethorus punctum were highly susceptible to methomyl. Eggs of Orius insidiosus were moderately susceptible. Chrysopa spp. eggs appeared to be unaffected by the material. LC₅₀ values for methomyl on eggs of Platynota spp. L. pomonella, O. insidiosus, Chrysopa spp., and S. punctum were generated. LC₅₀ values for P. ulmi eggs were unobtainable. Three rates of methomyl, used as an ovicide, were evaluated in the field for control of the Platynota spp. complex on apples compared to two formulations of FMC 45806, permethrin, and Bacillus thuringiensis. Methomyl provided the best control. Seasonal activity of P. flavedana and P. idaeusalis were monitored in reference to degree-day accumulations. Regression equations for male moth flights and egg deposition of the species are presented. Seasonal activity and prospects for development of a phenology model to predict seasonal activity of the species is discussed.