Moth pests are the most commonly reported arthropod groups to develop resistance to insecticides and cause serious agricultural damage worldwide. Therefore, there is a need to develop new insecticides for crop protection, but it is extremely difficult to discover insecticide seed compounds using lepidopteran pests as test organisms because of their low insecticide sensitivity. In this study, we constructed a highly sensitive insecticidal activity detection system using silkworm first instar larvae to obtain promising insecticidal compounds against moth pests. As the result of screening 724 substances in the O̅mura Natural Compound (O̅NC) library via this new silkworm system, borrelidin, a natural product derived from actinomycetes, was identified as an insecticidal compound for silkworms. Moreover, borrelidin also showed insecticidal activity on three species of moth pests. Here, we propose an efficient search method for insecticide seed compounds against moth pests, together with some verification results.

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Most natural products derived from microorganisms have been sought from actinomycetes and filamentous fungi. As an attempt to develop new microbial resources in the exploratory research for natural products, we searched for new compounds from unexploited microbial taxa presumed to have biosynthetic gene clusters. A new compound confluenine G (1) and a known compound (2Z)-2-octyl-2-pentenedioic acid (2) were isolated from a cultured broth of basidiomycetous yeast, Moesziomyces sp. FKI-9540, derived from the gut of a moth Acherontia lachesis (Lepidoptera, Sphingidae). Based on the results of HR-ESI-MS and NMR analyses, the planar structure of 1 was elucidated. Confluenine G (1) was a new analog of nitrogen-oxidized isoleucine and had rare substructures with oxime and hydroxamic acid in molecule

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