AMVAC 13821 SUMMIT B.T.I. BRIQUETS Mosquito Larvacide. For more than 35 years, fast-acting SUMMIT® B.T.I. BRIQUETS have been the industry standard in extended-release B.t.i. formulations for control of mosquitoes in the larval stage. Few products match their record of reliable and environmentally benign performance. SUMMIT B.T.I. BRIQUETS release the larvicide Bacillus thuringiensis isrealensis, a natural bacterium found in soils, which mosquito larvae ingest, dying before they become adults.