Evaluation of insecticide resistance in Louisiana adult mosquitoes and the efficacies of selected larvicides

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 Fyfanon® (96.8% malathion and Pyrocide ® (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). Fyfanon® caused significantly different (p < 0.05) mortalities among each species and strain within 24hrs (95% Aedes, 48% Denham Springs, and 14% Lake Charles). Pyrocide ® 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 μg/μl), and the Vermilion strain was most resistant (417.05 μg/μl). Resistance is based on a ≥5-fold resistance ratio. Calcasieu parish strain was least resistant to permethrin (1.93 μg/μl), and the St. Tammany parish strain was most resistant (40.86 μg/μl).; 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 (VectoBac® WDG and VectoBac® 12AS) and Bacillus sphaericus (VectoLex® WDG and VectoLex® 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).