Evaluation of Insecticide Resistance in Louisiana Adult Mosquitoes and the Efficacies of Selected Larvicides.
Date of Award
Doctor of Philosophy (PhD)
C. Lamar Meek
Pesticide resistance in Louisiana mosquitoes has never been examined on a state-wide basis. In 1996, first component of this monitoring program examined selected pesticide efficacies and documented current pesticide resistance. Ground ULV-applied FyfanonRTM (96.8% malathion and Pyrocide RTM (96.8% + 1% natural pyrethrum) were applied to caged Culex quinquefasciatus adults (Denham Springs [Livingston Parish] and Lake Charles [Calcasieu Parish]) and Aedes sollicitans (Vermilion Parish). FyfanonRTM caused significantly different (p < 0.05) mortalities among each species and strain within 24hrs (95% Aedes, 48% Denham Springs, and 14% Lake Charles). Pyrocide RTM also produced significantly different mortalities (99%, 70%, and 38%, respectively). Malathion and permethrin were topically applied to 3--5 day old adult mosquitoes from 14 parishes. St. Martin parish Cx. quinquefasciatus was most susceptible to malathion (2.58 mug/mul), and the Vermilion strain was most resistant (417.05 mug/mul). Resistance is based on a ≥5-fold resistance ratio. Calcasieu parish strain was least resistant to permethrin (1.93 mug/mul), and the St. Tammany parish strain was most resistant (40.86 mug/mul). Detecting pesticide resistance by bottle bioassay technique was compared to topical bioassay. Both techniques were effective in detecting resistance for selected Aedes, Anopheles, and Culex species in Louisiana. Ground ULV 97% malathion was applied to caged Cx. quinquefasciatus adults from a mosquito abatement district, agrichemical farmland, and a susceptible colony. No significance (p > 0.05) existed in mosquito mortality between the agrichemical area and the abatement district. Bacillus thuringiensis var. israeliensis (VectoBacRTM WDG and VectoBacRTM 12AS) and Bacillus sphaericus (VectoLexRTM WDG and VectoLexRTM CG) were applied by air and ground in ratoon rice against Culex larvae. Aerial VectoBac WDG produced poor control (<22%) of Cx. salinarius but excellent control (95%) at 24 hrs by ground application. Except for Day 9 (91% mortality), VectoBac 12AS caused <60% control of Culex. Aerial VectoLex WDG produced poor control (<45%) of Culex, but the ground-applied VectoLex WDG resulted in significantly greater Culex mortality (>70%) than the VectoBac formulations. Ground VectoLex CG produced the greatest Culex mortality (75--100% mortality for nine days), whereas aerial VectoLex CG resulted in poor control (<40% for the same period).
Bearden, Stacy Lee, "Evaluation of Insecticide Resistance in Louisiana Adult Mosquitoes and the Efficacies of Selected Larvicides." (2000). LSU Historical Dissertations and Theses. 7179.