Utilization of Agroindustrial Waste in the Propagation of Bacillus thuringiensis and its Toxicity to Oryctes rhinoceros Larvae

Abstract

Oryctes rhinoceros is one of the main pests that attack oil palm plantations. The use of entomopathogenic bacteria Bacillus thuringiensis is more effective and environmentally friendly than chemical control. The aim of this research was to study the effect of agroindustry waste in the propagation of B. thuringiensis and its toxicity to O. rhinoceros larvae. The research was conducted using a completely randomized design (CRD) consisting of 5 treatments with 4 replications including: P1: (rice bran + oil palm meal (2:1), P2: (rice bran + tofu dregs) (2:1), P3 (rice bran + peanut meal) (2:1), P4 (rice bran + corn stover) (2:1), P5 (water control) in a laboratory  (temperature range 23.34oC-26.01oC and relative  humidity range 51.25% - 78.14%). The test insects were 3rd instar O. rhinoceros larvae of 6 individuals per replicate. Bioassay test resulted the highest mortality rate (91.67%) was in treatment P1 (rice bran + palm kernel meal), while the lowest mortality rate (66.67%) was in treatment P3 (rice bran + corn husk). As a result of B. thuringiensis infection, larval body length and weight decreased every week. Symptoms of B. thuringiensis infection in larvae caused changes in body color from white to brownish to blackish, and cause the larvae's appetite to decrease. Finally,  larvae died in a softened and decomposed body with fluid coming out of the larval body. Bioinsecticide made from B. thuringiensis with mixed media of agricultural solid waste had been proven effective in killing O. rhinoceros larvae.