Evaluation of three microbial formulations against Culex pipiens pipiens larvae in irrigation fields in Wroclaw, Poland.

Two evaluations of microbial mosquito larvicides were conducted in irrigation fields located along the Odra River near the city of Wroclaw, Poland. In the first evaluation, 3 dosages each of Bacillus thuringiensis israelensis (Bti)--VectoBac water dispersible granule (WDG) and VectoBac aqueous suspension formulation (12AS)--and Bacillus sphaericus (Bs)--VectoLex WDG--were tested against larvae of Culex pipiens pipiens. There was little difference between formulations and rates of application between day 2 and 7 following the treatment. VectoBac WDG at 300 g/ha resulted in 100% mortality of Cx. p. pipiens. Between 0.5 and 1 liter of VectoBac 12AS caused sufficient mortality for up to 7 days. The effective shortterm application rate of VectoLex WDG was found to be 400 g/ha. The above doses can be recommended for up to 7-day control in this habitat. In the second evaluation, using VectoBac WDG at 800 g/ha, the residual efficacies of 2 ground application methods, a knapsack sprayer configured for large droplet application and a motorized backpack blower configured for small droplet application, were compared. The results indicated no significant difference between the 2 application methods, but a significant long-term effect of VectoBac WDG was observed at the rate of 800 g/ha.