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 short-term 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.