Two separate but related studies were conducted regarding management of Anopheles quadrimaculatus larval populations in commercial rice fields near Cleveland, MS, in 2004. Study 1 was to evaluate the effectiveness of 2 treatments of aerially applied ultra-low volume applications of Bacillus thuringiensis var. israelensis (Bti) against An. quadrimaculatus larvae in dense, high-canopy mid- to late-season rice crop. Study 2 was to investigate the effect of preflood treatments of lambda-cyhalothrin (Karate), which is commonly used against rice water weevil (Lissorhoptrus oryzophilus), on An. quadrimaculatus larvae. Excellent initial, but short residual control (>99% control 1 day after treatment) was observed in the Bti-treated fields in both mid- and late-season rice. Little or no effect on mosquito larvae was observed in the lambda-cyhalothrin-treated fields. Results indicate that Bti can be effectively used by mosquito management personnel to control larval populations of An. quadrimaculatus in late-season rice fields; however, lambda-cyhalothrin did not effectively control larval An. quadrimaculatus when applied preflood to rice fields.
Experiments were conducted to determine the residual efficacy of both a briquette and a granular formulation (2 rates) of a numbered spinosad compound against Psorophora columbiae larvae in small rice plots. Comparisons were also made between the numbered compounds and labeled granular and briquette formulations of methoprene. Both rates of the spinosad granules had the highest initial efficacy (100% control), with the spinosad briquette being the least effective. However, 1 wk after treatment, the spinosad briquette was equally effective to both spinosad granules, suggesting a slow release in the briquette. The experimental briquette and the high rate of the experimental granules had the most residual activity, providing over 80% control for 33 days posttreatment. The granular methoprene formulation was the least residually effective compound, providing only 12% control at 7 days posttreatment.
Field trials were conducted at 3 locations in Arkansas County, AR, to compare the effectiveness of 3 residential mosquito traps, the Stinger Mosquito Vacuum, the Mosquito Magnet Defender, and the Mosquito Deleto 2500 Active System, against riceland mosquitoes, specifically Anopheles quadrimaculatus and Psorophora columbiae. Both the Stinger Mosquito Vacuum and the Mosquito Deleto captured significantly more An. quadrimaculatus and total mosquitoes than did the Mosquito Magnet Defender. The Mosquito Deleto captured significantly more Ps. columbiae than did either of the other 2 traps.
Optimized aerial applications were conducted to assess the efficacy of 2 formulations of resmethrin (Scourge 18-54, Aqua-Scourge 10-30) for control of caged adult Anopheles quadrimaculatus. Micronair AU4000 rotary atomizers were employed to apply the chemical. Both compounds were applied at 0.0035 lb AI/acre (3.92 g AI/ha) with the use of the AGDISP computer model to predict appropriate flight offsets (up to 1,219.2 m). Efficacy was based on bioassays with caged An. quadrimaculatus adults and assessment of impinger-collected droplets. Both compounds provided effective mosquito control. Mean mortality at 24 h posttreatment averaged 80.4% for Scourge, and 80.7% for Aqua-Scourge. Mean droplet sizes, Dv0.5 = 26 microm and 38 microm, and mean density, 74 droplets/cm2 and 41 droplets/cm2, for Scourge and Aqua-Scourge, respectively, were consistent with the bioassay results. Analysis of droplet deposition and mortality failed to reveal a statistical correlation between mortality and deposit volume.
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