Presporangial mycelia of Lagenidium giganteum cultured on sunflower seed extract were encapsulated in calcium alginate and added once (July 18) to outdoor (Raleigh, NC) caged tires, wood and concrete containers populated with first instars of Culex quinquefasciatus or Aedes aegypti. First instars were added twice weekly (for 10 wk) to simulate natural oviposition. The fungus persisted for 10 wk and recycled in the mosquito larvae of both species. The overall reductions of Cx. quinquefasciatus and Ae. aegypti immatures were higher in tires (55 and 45%, respectively) and wood (67 and 38%) than in concrete containers (17 and 14%). There were low correlations of the numbers of mosquito immatures with measurements of water quality (chemical oxygen demand, ammonia nitrogen and conductivity) in the containers.