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dc.contributor.authorMetzger, Jessica A.en_US

Outbreaks of spider mites (Acari: Tetranychidae) in vineyards have been increasing with the expansion of the industry in Virginia. Only three effective acaricides are registered on grapes and as resistance begins to occur, control options are limited. Biological control of spider mites by inoculative or inundative releases of predatory mites has been tried on a wide range of crops including grapes. This project examined the feasibility of using Neoseiulus fallacis (Acari: Phytoseiidae) as a potential large-scale biological control agent in vineyards. Slide dip bioassays were conducted on N. fallacis to determine the toxicity of insecticides, fungicides and herbicides commonly used on grapes in Virginia. In addition to laboratory experiments, commercially obtained N. fallacis were released in vineyards with spider mite infestations. The populations of both mites were then monitored on a regular basis to determine dispersal and distribution patterns.

Among the insecticides tested in the laboratory bioassays, carbaryl, azinphos-methyl, phosmet, cyhexatin, and pyridaben all caused significantly higher mortality than the control treatment. Fungicides tested were not toxic to the predator, but three herbicides caused high mortality. Glufosinate caused 100% mortality after 24 hours and both oxyfluorfen and paraquat had adverse effects on N. fallacis. The use of materials that were found to be toxic to the predator would not be compatible with inoculative releases of N. fallacis.

Field release results were variable. Three releases were made in 1999 and 2000., Recovery of the predator was low following the releases at two of the sites, probably due to lack of prey. At the third site enough predators were recovered to analyze the spatial distribution of the predator and prey populations. It appears that there is no similar aggregation pattern between the predator and prey at the same point in time although there is an indication of the predator spreading is response to the prey distribution. A more complete season of sampling would give more conclusive evidence of this trend. Although the distribution of the two populations were dissimilar, the predator was present throughout the season and did spread through the entire plot indicating that the predator may be able to colonize the vineyard if it successfully overwinters.

dc.publisherVirginia Techen_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.subjectspider mitesen_US
dc.subjectNeoseiulus fallacisen_US
dc.subjectbiological controlen_US
dc.titleNeoseiulus fallacis (Garman) (Acari: Phytoseiidae) as a potential biological control agent for spider mites (Acari: Tetranychidae) in Virginia vineyardsen_US
dc.description.degreeMaster of Scienceen_US of Scienceen_US Polytechnic Institute and State Universityen_US
dc.contributor.committeechairPfeiffer, Douglas G.en_US
dc.contributor.committeememberKok, Loke T.en_US
dc.contributor.committeememberWolf, Tony K.en_US
dc.contributor.committeememberLewis, Edwin E.en_US

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