Abstract: This, paper is the first report on the efficacy of a Chinese produced Bacillus thuringiensis (Bt) wettable powder (16,000 IU) for the control of the peach fruit borer, Carposina niponensis. In the laboratory test, apple fruits were sprayed with the Bt wettable powder diluted 1,000 and 2,000 times, respectively and followed by introduction of newly hatched larvae of C. niponensis. The treatments provided a complete protection of the fruits for three days, with no infestation found on the third day after the treatment. This was similar to that obtained with 2.5% deltamethrin diluted at three different rates. However, introduction of the larvae on the third and sixth day after treatment with the Bt wettable powder resulted in 45.5% and 54.6% of larval mortality, respectively, indicating a relatively short residual effect of the product. A mixture of the Bt wettable powder with low concentration (2.5%) of deltamethrin showed a prolonged residual effect against the pest. The larval mortality on the third and sixth day after the treatment were 84.4% and 73.2%, respectively. This was similar to that obtained with 1,500 times of 50% parathion commonly used by growers in China.