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dc.contributor.authorBroeckling, Corey Daviden_US
dc.date.accessioned2011-08-06T14:45:04Z
dc.date.available2011-08-06T14:45:04Z
dc.date.issued2002-03-08en_US
dc.identifier.otheretd-03232002-152620en_US
dc.identifier.urihttp://hdl.handle.net/10919/9695
dc.description.abstractThe hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae), is forest pest introduced to eastern North America in the early 1950's. Although this pest occurs on both landscape and nursery stock as well as in natural stands of hemlock forest, pesticides are only practical and effective in urban settings. Ecological and economical considerations prevent utilization of chemical treatment in the forest setting, thus biological control is viewed as the most promising option for slowing the spread of HWA. It is essential for researchers to be able to accurately assess the population levels of biocontrol agents after release into the environment. No method currently exists for sampling HWA predators. This project was designed to determine whether two species of predators are able to utilize olfactory cues from eastern hemlock and/or HWA in host-finding. If predators use olfactory cues, we may develop an attractive sythnetic blend of compounds to draw them to a trap, thereby simplifying the sampling and improving its accuracy. To address this question we executed three experiments. The first involved examination of the antennae of the predators for the presence and abundance of olfactory sensilla. The second experiment was designed to detect a behavioral response by the predators following exposure to host volatile compounds. The final experiment involved identifying compounds emitted from eastern hemlock, and the affect of HWA-feeding on volatile emissions. Laricobius nigrinus Fender (Coleoptera: Derodontidae) antennae are densely populated with sensilla, several of which are potentially olfactory in function. In addition, we observed a behavioral response to olfactory cues which included altered flight behavior. However, the behavior was not clearly attraction. Pseudoscymnus tsugae Sasaji and McClure (Coleoptera: Coccinellidae) has few sensilla on a very short antennae and only one type of sensilla possesses wall pores suggestive of an olfactory function. In addition, we did not observe a significant behavioral response to host-volatiles. It seems unlikely that this species uses olfaction in long-range host location. We identified 10 monoterpenes that were consistently expressed in the hemlock volatile profile and were unable to isolate volatile emissions from HWA. There is an increased monoterpene release rate from HWA-infested hemlock foliage as compared to uninfested foliage apparently driven indirectly by HWA through a reduction in new growth at branch tips. In addition there was a slight but statistically significant change in the percent composition of the individual compounds. We see potential in developing a more efficient sampling procedure for L. nigrinus through utilization of olfactory cues. More biological assays must be conducted to determine whether an attractive blend exists and electrophysiological assays are required to isolate physiologically active compounds. However, our data suggest that P. tsugae is not likely to be reliant on olfaction in long-range host location.en_US
dc.format.mediumETDen_US
dc.publisherVirginia Techen_US
dc.relation.haspartthesis_text.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectpseudoscymnus tsugaeen_US
dc.subjecttsuga canadensisen_US
dc.subjectentomologyen_US
dc.subjectlaricobius nigrinusen_US
dc.subjectadelges tsugaeen_US
dc.subjectvolatile compoundsen_US
dc.subjectbehavioren_US
dc.subjectantennaeen_US
dc.subjectmorphologyen_US
dc.subjectolfactionen_US
dc.titleThe role of olfaction in host-finding by two specialist predators of hemlock woolly adelgiden_US
dc.typeThesisen_US
dc.contributor.departmentEntomologyen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineEntomologyen_US
dc.contributor.committeechairSalom, Scott M.en_US
dc.contributor.committeememberFell, Richard D.en_US
dc.contributor.committeememberSeiler, John R.en_US
dc.contributor.committeememberDickens, Joseph C.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03232002-152620en_US
dc.date.sdate2002-03-23en_US
dc.date.rdate2003-05-02
dc.date.adate2002-05-02en_US


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