The potential for long term mosquito larval reduction by Bacillus thuringiensis serotype H-14, B. sphaericus and Metarhizium anisopliae was tested using laboratory simulations of flooded field breeding sites. Results showed that the capability of either bacterial species to reduce larval numbers was lost as early as 1 month after bacterial inoculation. Replicates receiving the fungal pathogen did show reduced mosquito emergence up to 150 days after fungus introduction, but by day 224 mosquito populations were not affected.