Donald Cipollini, Ph.D. (Advisor); Pierluigi Bonello, Ph.D. (Committee Member); Daniel A. Herms, Ph.D. (Committee Member); John O. Stireman, III, Ph.D. (Committee Member); William Romine, Ph.D. (Committee Member)
Doctor of Philosophy (PhD)
North American and European ash trees are highly susceptible to emerald ash borer (EAB, Agrilus planipennis). This buprestid kills hosts via larva feeding on vascular tissue which eventually kills the host plant. Two new hosts have recently been found to support larval development of EAB. White fringetrees (Chionathus virginicus) were found attacked by EAB in 2014 and since then have been found to be attacked throughout other parts of the United States, while olive (Olea europaea) has only experimentally been found to support larvae to adulthood. Chemical profiles of these two plants were collected and analyzed to determine how their volatile emissions vary among susceptible and resistant ash trees. Additionally, larvae and adult beetles were tested for their performance on these novel plants. For white fringetree, wild populations were monitored to determine the impact of EAB during the attack wave. These studies find that white fringetree foliage supports adults, but when phloem is healthy it causes high larval morality in contrast to girdled or previously attacked by EAB where larvae survived by the end of assays. In the field, EAB began to use white fringetree quickly, within a couple of years after initial exposure. Female choice suggests white fringetree and susceptible ash are similarly preferred likely due to the similar volatile emissions. These chemicals likely caused host range expansion of EAB to this novel host. In contrast to ash, the impact of EAB on white fringetree is minimal. This plant mostly loses a branch or two from larval girdling, which in ornamentally planted fringetrees can be aesthetically displeasing. On olive, EAB is likely to be even less damaging because larvae take longer to develop than in ash and larvae die quickly in young, photosynthesizing stems. Adults did not perform well because oleuropein may cause them to compensatory feed and causing malnutrition. In North American forests, if EAB continues to destroy ash species at such high rates, EAB may be driven to use white fringetree more often. With continued use of this host, EAB is likely to adapt to better utilize white fringetree which could eventually lead to host switching.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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