Preliminary study of insecticidal effect of citronella grass essential oil (Cymbopogon nardus) against post harvest pest Sitophilus oryzae

Abstract

Sitophilus oryzae is one of major postharvest pest in rice. It damaged the grain quantitatively and qualitatively (decreasing the product hygiene and causing the residue of its excretion). The research used natural insecticide comprise citronella grass which is a promising botanical insecticide to be used for controlling postharvest pest. This research has been conducted in the laboratory of Entomology, Indonesian Spice and Medicinal Crops Research Institute (ISMECRI) in January to March 2020. Citronella grass was distilled to obtain its essential oil containing 39% of citronella and 86% of geraniol. The research consisted of three methods, i.e. (a) repellent, designed by Completely Randomized Design, 5 treatments (concentration at 10%; 7.5%; 5%; 2.5%; and 1.25%), and 5 replications; and toxicity by using probit analysis applied by (b) contact; and (c) residue. The result revealed the oil may repel 33% at concentration of 10%, followed by concentration of 7.5%; 5% and 2.5% may repel as much as 24.6%; 20.4% and 10.8% consecutively. The LC50 of contact and residue toxicity are 23.2% and 1.71%. Applied by residual is more toxic than by contact. This showed that citronella grass essential oil has good prospect as natural insecticide to control S. oryzae, therefore the research need to be elaborated.