Koch, Karrie Anne2011-08-172011-08-172011-07https://hdl.handle.net/11299/113174University of Ph.D. dissertation. July 2011. Major: Entomology. Advisor: Dr. David Ragsdale. 1 computer file (PDF); vii, 171 pages.Soybean aphid, Aphis glycines Matsumura, is an invasive arthropod pest of soybean which has been present in North America since 2000. Aphid outbreaks cause economic damage via increased insecticide use and reduced yield. Management of this pest has been achieved almost exclusively with foliar applications of broad spectrum insecticides. The purpose of this research is to determine how a fungal pathogen of soybean aphid, Pandora neoaphidis, can contribute to the natural regulation of aphid populations. Pandora neoaphidis is an endemic aphid pathogen and the most frequently reported pathogen infecting soybean aphid. Analysis and field validation of a mathematical model describing the soybean aphid-P. neoaphidis pathosystem has shown that the fungus can establish and persist when aphid densities are lower than the economic threshold of 250 per plant; thus confirming that P. neoaphidis is capable of contributing to aphid control before aphids reach damaging densities. Additionally, field experiments demonstrate that emerging aphid management tactics including aphid-resistant soybean plants and insecticide seed treatments have minimal impacts on aphid infection rates by P. neoaphidis and are likely compatible with this natural enemy. Cage studies demonstrate that the presence of Harmonia axyridis in soybean aphid colonies also harboring P. neoaphidis has no impact on aphid infection by the fungus. Pandora neoaphidis may also be an important regulator of aphid populations on the aphids’ primary host, Rhamnus cathartica, or common buckthorn, as soybean aphid morphs which occur on this host are the most susceptible to infection. However, fungicide applications to soybean can have lasting impacts on the beneficial fungi infecting soybean aphid as foliar fungicide applications to soybean reduced the rate of aphid infection both before and after aphids moved to the primary host in the autumn. In summary, P. neoaphidis is likely an important member of the natural enemy community which provides a significant level of aphid biological control.en-USAphis glycinesBiological ControlIPMPandora neoaphidisEntomologyThesis or Dissertation