Six different types of alginates used to encapsulate Lagenidium giganteum gave similar levels of fungal infection in Culex quinquefasciatus larvae. Initial infection levels when the capsules were immersed in water after 6 days of storage (15 and 25 degrees C) were 100% for all types of alginate and after 42 days of storage was 62-100%, depending on the type of alginate. Infectivity was 24-100% after the encapsulated fungus were left in water for 7 days and after 15 days was 0 to 26%, depending on the alginate. When 2 of the alginates were tested at different concentrations to give high, medium and low viscosity solutions, the fungus encapsulated using lower concentration alginate solutions usually gave the highest level of infectivity.