UVM Theses and Dissertations
Format:
Print
Author:
Pears, Sarah L.
Dept./Program:
Natural Resources
Year:
2011
Degree:
MS
Abstract:
Sirex noctilio Fabricus (Hymenoptera: Siricidae), a woodwasp native to Europe, Asia and North Africa, was found in New York in 2004. The wasp has spread as an invasive insect within eastern North America. The potential for loss of Pinus (Pinaceae: Pinus) trees, S. noctilio's preferred hosts in North American forests is not well understood. One potential reason for S. noctilio's successful establishment as a nonnative species is its symbiotic relationship with Amylostereum areolatum (Russulales: Stereaceae), a white rot fungus. When S. noctilio females oviposit in stressed Pinus trees, they deposit eggs, a phytotoxic mucus and arthrospores of A. areolatum. We studied the interactions of A. areolatum and Pinus strobus (Pinaceae: Pinus) and Pinus resinosa (Pinaceae: Pinus) in an experimental field study.
We measured host tree water potential, photosynthesis, resin flow, and lesion length prior to inoculating trees with A. areolatum and a control blank agar treatment and at 3D-day intervals post-inoculation. Tree vigor was assessed at the time of stress treatments, inoculation, and at the end of the experimental period. Our results suggest that A. areolatum is likely not capable of causing host mortality, even of highly stressed hosts, without the presence of S. noctilio and the phytotoxic mucus the female woodwasp injects into the host during oviposition. We noted that staining resulting from inoculation with A. areolatum is similar in P. strobus and P. resinosa in Vermont to reddish-brown staining reported in the Southern Hemisphere, where S. noctilio is also invasive.
During the course of the study we noted that some of our study trees were attacked by the native herbivorous insect-fungi complex, Ips (Coleoptera: Scolytidae) and Ophiostoma (Ophi, ostomatales: Ophiostomataceae) species. We report observed interactions between the fungi and impacts of these relationships on host tree physiology and defense, and suggest a theoretical framework for work further examining interactions between the S. noctilio complex and native North American herbivore-fungi complexes in North American forests.
We measured host tree water potential, photosynthesis, resin flow, and lesion length prior to inoculating trees with A. areolatum and a control blank agar treatment and at 3D-day intervals post-inoculation. Tree vigor was assessed at the time of stress treatments, inoculation, and at the end of the experimental period. Our results suggest that A. areolatum is likely not capable of causing host mortality, even of highly stressed hosts, without the presence of S. noctilio and the phytotoxic mucus the female woodwasp injects into the host during oviposition. We noted that staining resulting from inoculation with A. areolatum is similar in P. strobus and P. resinosa in Vermont to reddish-brown staining reported in the Southern Hemisphere, where S. noctilio is also invasive.
During the course of the study we noted that some of our study trees were attacked by the native herbivorous insect-fungi complex, Ips (Coleoptera: Scolytidae) and Ophiostoma (Ophi, ostomatales: Ophiostomataceae) species. We report observed interactions between the fungi and impacts of these relationships on host tree physiology and defense, and suggest a theoretical framework for work further examining interactions between the S. noctilio complex and native North American herbivore-fungi complexes in North American forests.