Streptomyces has been reported to produce various secondary metabolites which have the potential to become environmentally safe insecticides. In this study, 1,274 streptomyces culture filtrates were screened for their JHAN activity in order to identify novel insecticidal compounds. 34 isolates with high levels of JHAN activity were selected, and their insecticidal activities were tested against Plutella xylostella larvae. Among them, IMBL-263 which was revealed to be Streptomyces anulatus by 16s rRNA sequencing showed the highest insecticidal activity. Also, systemic activities of secondary metabolites extracted from the S. anulatus on plant, Brassica napus, were investigated. These results suggested that secondary metabolites from the S. anulatus might be useful for development of novel environmentally benign insecticides.

Widespread use of chemical insecticides has resulted in development of insect resistance and natural products withbiological activities could become an attractive alternative to control insect pests. In order to find more effective insecticidesfor controlling mosquito, various mosquitocidal compounds are studied. Recently, juvenile hormone antagonists (JHANs)are known to be to safe and effective insecticides for control mosquito. In order to identify novel insecticidal compoundswith JHAN activity, several chalcones were surveyed on their JHAN activities and larvicidal activities against Aedes albopictuslarvae. Among them, 2’-hydroxychalcone and cardamonin showed high level of JHAN and mosquito larvicidal activities.These results suggested that chalcones with JHAN activity could be useful for control of mosquito larvae.

Plant essential oils have been reported to show repellent, insecticidal and growth-reducing effect on many insect herbivores. Recently, it has been reported that plants synthesize secondary metabolites regulating insect juvenile hormone (JH) receptor complex as a part of their defense mechanisms. We tested 180 plant essential oil compounds using a yeast two-hybrid system transformed with the Aedes aegypti JH receptor as a reporter system. Among them, we identified 17 compounds that showing high JH agonist (JHA) or antagonist (JHAN) activities. They were grouped into 4 groups by their structural similarity and their insecticidal activity was tested against larvae of Aedes albopictus, Plutella xylostella, Plodia interpunctella and Laodelphax striatellus. These results could provide insights on the plant-insect coevolution and may be useful for the development of insect specific and safe pesticides.