ABSTRACT
Laboratory bioassays using a preparation of Bacillus thuringiensis H-14 (Bt.H-14), namely Skeetal were conducted to determine their effectiveness against late 3rd/early 4th instar larvae of Aedes aegypti. The larvae were collected from municipal areas in 7 provinces, namely Burirum, Roi-Et, Khon Kaen, Ubol Ratchatani, Nakorn Phanom, Surin and Nakorn Ratchasima, in the Northeast of Thailand. It was found that for Skeetal, LC50 ranged from 128 to 151 nl/l (average 143) and LC90 ranged from 254 to 289 nl/l (average 275). The mortality rate of Ae. aegypti larvae in the 7 provinces did not differ significantly (p greater than 0.05) at a concentration of 300 nl/l. The result of the bioassays show that the preparation of Bt.H-14 is very effective against Ae. aegypti larvae in Northeast of Thailand and the mosquito larvae in the various areas were nearly equal in susceptibility to Bt.H-14.