Pesticidal Activities and Effect on Its Biological Characteristics of Bacillus thuringiensis Strains from Soil against Rice Pests, Cnaphalocrosis medinalis and Maranga aenescens

벼에 발생하여 잎을 가해하여 피해를 주는 혹명나방(Cnaphalocrosis medinalis)과 벼애나방(Naranga aenescens)의 곤충병원성미생물을 이용한 친환경적 방제를 위해, 국내토양에서 분리된 Bacillus thuringiensis 균주들을 대상으로 생물검정을 수행하였다. 실험에 이용한 Bt 53균주 중, 약 18개 균주가 혹명나방에 90% 이상의 살충률을 나타내었고, 13개 균주가 벼애나방에 살충활성을 보였는데, 두 종 모두에 90% 이상의 살충률을 보이는 균주도 CAB141균주를 비롯해 11균주나 확인되었다. 이러한 균주들은 혹명나방에 대한 실내방제실험결과, 96%이상의 방제효과를 나타내기도 하였다. 또한 Bt 포자현탁액에 노출된 유충의 용화율, 용길이, 우화율이 감소되는 경향이 나타났는데, 혹명나방의 경우, 번데기 길이에서도 정상개체와 처리 후 생존개체가 현저한 차이를 나타내었다. For biological control of larva of Cnaphalocrocis medinalis and Naranga aenescens do considerable damage to crops by folding and scraping the leaf tissue of rice, a large number of Bacillus thuringiensis isolates have been obtained from soil samples in Korea and the pesticidal activity was assayed against two insect pest species described above. Among 53 Bt isolates tested in bioassay, 18 and 13 isolates showed over 90% mortality against C. medinalis and N. aenescens, respectively. Some isolates (11 isolates including CAB141) presented dual activity against C. medinalis and N. aenescens. These isolates showed over 96% control effect in pest control in laboratory against larvae of C. medinalis. Also, it was investigated that pupation, pupal length, and adult emergence of larvae exposed to Bt suspension decreased. Especially, the pupal length of C. medinalis after being fed corn seedling leaves treated Bt suspension for 10 days, were much smaller than that of control.