Evaluation of methylated soy oil and water-based formulations of Bacillus thuringiensis var. israelensis and Golden Bear Oil (R) (gb-1111) against Anopheles quadrimaculatus larvae in small rice plots

The efficacy of formulations containing methylated soybean oil (MSO) alone and with technical-grade Bacillus thuringiensis var. israelensis (Bti) were compared to Golden Bear Oil(R) (GB-1111) and a waterbased Bti formulation against 3rd- to 4th-stage Anopheles quadrimaculatus larvae confined to sent inel cages in small rice plots. Three replicates each of MSO with 2% Pyrote r(R) added as a surfactant (MSO + PYR), MSO with 2% Pyroter and 4 g of Bti technical powder (MSO + PYR + Bti), GB-1111, a water-based formulation with 4 g of Bti technical powder (Bti + water), and untreated controls were per formed. Mosquito larvae were introduced on the Ist day of treatment and at 4 days posttreatment. Mortality was recorded at 24 and 48 h posttreatment f or the 1st installation and at 5 days posttreatment for the 2nd installatio n. The Bti + water formulation provided 71% control and the MSO + PYR + Bti formulation achieved 64% control, whereas MSO + PYR and GB-1111 produced 1 6 and 18% control, respectively, at 24 h posttreatment. With the exception of MSO + PYR + Bti, which decreased by 2%, the mean percent control increas ed slightly at 48h posttreatment across remaining treatments, with Bti + wa ter obtaining 72% control. This was significantly higher than GB-1111, whic h achieved 23% control at 48 h posttreatment. The MSO + PYR and MSO + PYR Bti formulations yielded 56 and 62% control, respectively, during the same interval and were not significantly different from one another. Formulatio ns containing MSO + PYR exhibited delayed activity similar to GB-1111, with all formulations except MSO + PYR + Bti providing greatest control at 48 h posttreatment. Both MSO formulations (MSO + PYR + Bti and MSO + PYR) were statistically comparable to Bti + water and GB-1111, respectively, at 24 an d 48 h posttreatment. None of the formulations exhibited a residual activit y adequate enough to control An. quadrimaculatus larvae for up to 5 days.