Effects of insecticides on potato leafhoppers Empoasca fabae (Harris) and its predators

dc.contributor.authorMartinez, Danilo G.en
dc.contributor.departmentEntomologyen
dc.date.accessioned2014-03-14T21:29:15Zen
dc.date.adate2009-02-13en
dc.date.available2014-03-14T21:29:15Zen
dc.date.issued1979en
dc.date.rdate2009-02-13en
dc.date.sdate2009-02-13en
dc.description.abstractSelected insecticides were evaluated to determine effects on the potato leafhopper and its predators. Three types of tests were conducted. First, the common predators of the potato leafhopper in alfalfa were examined to determine their response to the stages of the leafhopper. Second, under field conditions, insecticides were tested to detect effects on the populations of the insects. Finally, LC₅₀ toxicities of selected insecticides were investigated under laboratory conditions. In the predation tests, two studies were conducted, namely, predation on egg stage and predation on nymphal and adult stages of the potato leafhopper. An indirect method of determining egg predation was employed because potato leafhopper eggs are not visible, being concealed in the xylem and phloem tissues. Using two sets of treatments (with and without predators), the potato leafhopper females were allowed to oviposit in predation cages and the suspected predators introduced thereafter. Hatching nymphs were counted and used as indications of the number of eggs laid. Nabis americoferus and Orius insidiosis were found to be predaceous on eggs of the potato leafhopper. In the predation tests, using nymphal and adult stages of the potato leafhopper, the following adult and larval stages of insects were confirmed as predators: Hippodamia convergens, Coccinella novemnotata, and Chrysopa carnea. Two field tests, one in summer of 1977 and one in summer of 1978, were conducted to determine the influence of insecticides on populations of potato leafhoppers and its predators in alfalfa. Samples were taken using a 38 cm sweep net employing a 180° motion at 2 days, 1 week, and 2 weeks after treatment. In both tests, significant control was provided by the chemicals against potato leafhoppers 48 hours following application. A gradual population recovery occurred one week and two weeks after treatment. Most of the entomophagous insects sampled were adversely affected by insecticides. No statistical differences in yield and percent dry matter were obtained with various insecticidal treatments. The acute toxicities of selected insecticides on potato leafhopper, tarnished plant bug, and damsel bug were investigated. The bioassay method used was the immersion technique and toxicity was expressed in LC₅₀. The relative toxicities of Nabis americoferus to 50° Empoasca fabae and Lygus lineolaris were obtained by deriving the selectivity ratios. Selectivity ratios are calculated by dividing the LC₅₀ of the non-target organism divided by the LC₅₀ of the pest. The ratios indicated that most of the insecticides tested were highly selective. Among the organophosphates, azinphosmethyl was the most selective, while among the carbamates, carbaryl was the most selective.en
dc.description.degreeMaster of Scienceen
dc.format.extentvii, 73 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-02132009-172118en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-02132009-172118/en
dc.identifier.urihttp://hdl.handle.net/10919/41074en
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1979.M3771.pdfen
dc.relation.isformatofOCLC# 05181728en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1979.M3771en
dc.subject.lcshAlfalfa -- Diseases and pestsen
dc.subject.lcshEmpoasca fabaeen
dc.subject.lcshHomopteraen
dc.subject.lcshInsecticidesen
dc.subject.lcshLeafhoppersen
dc.titleEffects of insecticides on potato leafhoppers Empoasca fabae (Harris) and its predatorsen
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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