First Report: Senna multijuga Subsp. multijuga (Fabales: Fabaceae) as an Attractant and Bioinsecticide for Oryctes rhinoceros (Coleoptera: Scarabaeidae)

Abstract

In 2020, a plant displaying promising attributes as both an attractant and bioinsecticide for Oryctes rhinoceros (Coleoptera: Scarabaeidae), known locally as “Hujan Emas”, was discovered at PT Sampoerna Agro Tbk, Indonesia. Despite its potential, the identity of this plant remains unknown. This study aims to reveal the plant’s identity and ascertain its potential as an attractant and bioinsecticide against O. rhinoceros. Identification was performed using morphological and sequence analyses of the MaturaseK, chloroplast rps16, and chloroplast rpl16 genes. Field observations were conducted over 9 months, focusing on the number of adult O. rhinoceros visiting the plant and the number captured using synthetic pheromone (ethyl 4-methyloctanoate) traps. Bioinsecticidal activity assessments focused on extracts from the plant’s bark, stem, and leaves. Morphological characterization and sequence analysis conclusively affirmed the plant’s identity as Senna multijuga (Fabales: Fabaceae). The total number of O. rhinoceros specimens obtained from S. multijuga was 1.6 times higher (836 beetles) than that obtained using the pheromone trap (512 beetles), suggesting that S. multijuga has better attractant capability than ethyl 4-methyloctanoate. The leaf extract exhibited insecticidal activity against larvae, while the stem and bark extracts demonstrated insecticidal activity against both larvae and adults. Larval mortality ranged from 1.25% to 3.75%, while adult mortality was notably higher, ranging from 12.5% to 25%. This is the first report on the capability of S. multijuga as an attractant and bioinsecticide against O. rhinoceros.