An analysis of the establishment and impact of an exotic insect, Rhinocyllus conicus Froehling (Coleoptera: Curculionidae), on Carduus nutans L. and Carduus acanthoides L. (Campanulatae: Compositae) in Virginia with notes on their biologies

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dc.contributor.authorSurles, Walter Wayneen
dc.contributor.departmentEntomologyen
dc.date.accessioned2014-03-14T21:38:52Zen
dc.date.adate2009-06-17en
dc.date.available2014-03-14T21:38:52Zen
dc.date.issued1972en
dc.date.rdate2009-06-17en
dc.date.sdate2009-06-17en
dc.description.abstractStudies over a two-year period were undertaken to evaluate the potential and effect of Rhinocyllus conicus as a biological control agent for Carduus nutans and C. acanthoides in Virginia. Over an 81 day range, 25 females oviposited an average of 100.5 eggs. Life expectancy did not differ between sexes. Examination of 1999 C. nutans plants in Pulaski Co. showed: 26.7% of all blooms were infested (46.7% terminals and 18.2% laterals); no weevil orientation relative to plant density but a preference for terminal blooms and no bloom size preference for oviposition. Evaluation of 261 capitula revealed that an infested bloom produced 37 mature seeds/mm of diameter. Each larva destroyed 9.7 achenes. Weevil mortality on C. nutans capitula occurred primarily during the egg stage (58.3%). Mechanical egg dislodgement was not a major mortality factor. Ege and/or adult parasitism was not observed. Aliolus curculionis, Bracon mellitor, and Campoplex polychrosidis parasitized the weevil larvae and pupae. Twelve other possible parasites were collected. Crowding was not a significant mortality factor. An egg maturation of 31.9% was noted, and 3.1 weevils emerged per infested bloom. Mortality among sites ranged from 56.1% (adjacent to trees) to 95.8% (unprotected). Weevil adults exhibited thigmotaxis by overwintering in the cracks of the framework of a large outdoor rearing cage. They apparently preferred this site rather than soil litter and debris. Best release establishment and dispersal occurred on C. nutans which was preferred to Carduus acanthoides.en
dc.description.degreeMaster of Scienceen
dc.format.extent186 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06172009-063016en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06172009-063016/en
dc.identifier.urihttp://hdl.handle.net/10919/43363en
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1972.S915.pdfen
dc.relation.isformatofOCLC# 38878546en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1972.S915en
dc.titleAn analysis of the establishment and impact of an exotic insect, Rhinocyllus conicus Froehling (Coleoptera: Curculionidae), on Carduus nutans L. and Carduus acanthoides L. (Campanulatae: Compositae) in Virginia with notes on their biologiesen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineEntomologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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