Bacillus thuringiensis, a green option for controlling oil palm bunch moth Tirathaba rufivena

Abstract

A field study to test the efficacy of Bacillus thuringiensis subsp. Kurstaki against Tirathaba rufivena, the oil palm bunch moth, has been conducted in early mature (5-year-old) oil palm in Kalianta Estate, Riau. The experiment was conducted following a randomized complete block design, consisting of five concentration treatments, namely 0, 2, 4, 6, and 8 ml/L of suspension. The B. thuringiensis was sprayed directly onto the inflorescences and fruit bunches of selected palm samples every week for a month duration. The result showed that the intensity of T. rufivena attack was continuously declined since the first week after B. thuringiensis application. The decline of attack intensity is in line with the reduction of the larvae population in the affected fruit bunches. This trial demonstrated that B. thuringiensis had high efficacy against the bunch moth with an efficacy value of 74.90 %, 91.18 %, 96.96 %, and 94.77 % achieved at two weeks after application at the concentrations of 2, 4, 6, and 8 ml/L, respectively. This result suggests that B. thuringiensis at the concentration of 4-8 ml/L can be used as a sustainable option for controlling T. rufivena in oil palm plantations.