Host range and selected factors influencing the mosquito larvicidal activity of the PG-14 isolate of Bacillus thuringiensis var. morrisoni.

ABSTRACT

Laboratory bioassay of the PG-14 isolate of Bacillus thuringiensis var. morrisoni (serotype 8a8b) against early fourth instar larvae of 8 species of mosquitoes revealed a range of susceptibilities similar to the susceptibilities of these species to Bacillus thuringiensis var. israelensis (serotype 14). The most susceptible species were Culex quinquefasciatus, Cx. salinarius, Anopheles albimanus and Aedes aegypti. The least susceptible species tested was An. quadrimaculatus. Separate bioassays of PG-14 against the four instars of Ae. aegypti demonstrated a strong negative correlation (R = -0.97) between larval age and susceptibility. Temperature significantly affected the stability of larvicidal toxin in aqueous suspensions of PG-14. Larvicidal activity of a bacterial suspension was nearly completely eliminated after 132 days of storage at 31 degrees C, but was essentially unchanged for those suspensions stored at 4 degrees C.