Evaluation of the Safety of Bacillus thuringiensis Strain YJ-2000 to the Silkworm, Bombyx mori and its Insecticidal Activities Against Other Lepidopterous Species

Insecticidal activities of Bacillus thuringiensis strain YJ-2000 against six species of lepidopterous insects were evaluated with the time-dose-mortality mode. The strain was safe to the silkworm, Bombyx mori with very low toxicity, while showed the toxicity with different levels to vegetable insect pests such as Pieris rapae neonate larvae and 2nd instar larvae of Plutella xylostella, rice insect pests such as neonate larvae of Chilo suppressalis and Scirpophaga incertulas as well as mulberry insect pests such as 3rd or 4th instar larvae of Diaphania pyloalis. Among tested insect species, larvae of Plutella xylostella and Pieris rapae were the most susceptible to the strain, with the highest mortality of 100% .It is implied that the strain is a specific one both with the safety for the silkworm and the toxicity to other lepidopterous species and has a great potential for being utilized in microbial control of lepidopterous species on the mulbery and other crops near the mulberry garden.