Ice granules containing endotoxins of microbial agents for the control of mosquito larvae--a new application technique.

This study investigated a new method for delivering microbial mosquito control agents into aquatic sites as ice granules for mosquito control. Solutions containing powder formulations of Bacillus thuringiensis israelensis (Bti) or Bacillus sphaericus were transformed into ice pellets (named IcyPearls) using a special ice-making machine. This new technique was demonstrated to have the following advantages over Bti sand granules: 1) the Bti ice pellets melted on the water surface and released the microbial crystals there; 2) the control agent remained inside the ice pellets during the application and were not lost by friction in the spraying equipment; and 3) the ice formulation resulted in increased swath widths, significantly reducing the cost of application. In large field tests. IcyPearls have been applied at dosages of 5 and 10 kg/ha containing 400 g as well as 100, 200, and 400 g of VectoBac WDG (3,000 ITU/mg), respectively, against larvae of Aedes vexans. Mortality rates of 91-98% were achieved.