Insect community in sengon (Falcataria moluccana) stands damaged by stem borers at various altitudes

Abstract

Abstract. Sutrisno YA, Triyogo A, Suryanto P. 2022. Insect community in sengon (Falcataria moluccana) stands damaged by stem borers at various altitudes. Biodiversitas 23: 3234-3242. A healthy ecosystem is characterized by a balanced interaction between its constituent components. Meanwhile, sengon or Falcataria moluccana stands are one of the ecosystems currently experiencing damage due to stem borer pests. The dominance of pests leads to an imbalance between the constituent components of the ecosystem, especially insects. Therefore, this study aims to examine the characteristics of the community and the role of each insect, as well as the pattern of relationships with the stem borer attack area. It was conducted in a 5-year-old sengon stand in the Cangkringan Sub-district, Sleman, Yogyakarta, Indonesia, at altitudes of 500, 600, and 700 m above sea level (asl), while observations and insect collection were carried out from March to August 2018 using pitfall and sticky traps, as well as sweeping nets. Furthermore, direct identification, specimens, and references were used to determine the insects to the morphospecies level, while the diversity (H'), evenness (E), and similarity (S) indexes were calculated to describe the community. The two-way ANOVA analysis was conducted to determine the effect of altitude and observation month on insects at the family level, while a correlation analysis was performed to determine the relationship between insect diversity and the stem borer attack area. The results showed that the insect community in the sengon stands consisted of 14 orders, 49 families, with 104 morphospecies. The most abundant was Family Formicidae (Hymenoptera) and the classification was based on the respective roles obtained in five groups, namely herbivores, predators, pollinators, parasitoids, and decomposers. The observation month, altitude, and interaction have different effects on insects at the family level, which includes Eucharitidae, Tephritidae, and Cicadellidae. Moreover, the abundance of Eucharitidae parasitoids decreased with an increase in altitude, while the herbivores with the highest abundance were Tephritidae at an altitude of 500, 700, and 600 m, as well as Cicadellidae at an altitude of 500, 600, and 700 m above soil level, respectively. Natural predators dominated by Formicidae (Hymenoptera) showed a similar tendency at every altitude and observation month. Based on the results, the higher the level of insect diversity in the form of population and species, the lower the stem borer attack area. Therefore, further observations need to be carried out on the natural predator found, including specialists or generalists, to obtain the most suitable for controlling stem borers.