Date of Award
Environmental and Forest Biology
Christopher M. Whipps
Melissa K. Fierke
Sirex noctilio Fabricius. (Hymenoptera:Siricidae) is an invasive xylophagous woodwasp native to Eurasia and introduced to North America. Introduction of this invader in the southern hemisphere resulted in widespread economic damage of the pine industry, however, it is apparently exerting less harm to North American forests. This is possibly due to the presence of native parasitoids that attack S. noctilio. The purpose of this study was to identify parasitoids of S. noctilio, and the native Sirex nigricornis Fabricius based on DNA sequence analysis of larvae using cytochrome oxidase I, cytochrome b, and ribosomal large subunit genes. These sequences were used to evaluate sequence diversity within each genus and species, and examine spatial distributions of genotypes and host-specificity. Specimens were collected from sites in New York and Pennsylvania. Parasitoid larvae were first morphologically categorized as either Ibalia species or rhyssines (Ichneumonidae: Rhyssinae) based on size, mandible morphology, and body structure. Sequence diversity was analyzed and specimens assigned to a genus and a letter designating sequence type: Ibalia A-H, Pseudorhyssa A&B, Megarhyssa A-C and Rhyssa A-E. Interestingly, Rhyssa B was the only sequence type found in our native siricid, S. nigricornis, while all other genotypes were found only in S. noctilio. There was no pattern of site specificity for the species types in this study, suggesting parasitoids were not isolated to certain locations. Because several parasitoid types exhibited host specificity to S. noctilio, it appears biocontrol of this invasive woodwasp is already occurring on the landscape by several species.
Weinstein, Ilana, "Establishing Host-parasitoid Linkages among Sirex noctilio, Sirex nigricornis," (2018). Honors Theses. 129.