in vitro bioassay of certain botanical oils for their efficacy against maize fall army worm (J.E. Smith) Spodoptera frugiperda (Noctuidae: Lepidoptera)

Abstract

Maize, Zea mays is one of the world’s main agricultural crops and Spodoptera frugiperda (J. E. Smith) is the most devasting invasive pest. This study evaluates the effect of plant oils on the third instar larvae of Spodoptera frugiperda. The experimental design was completely randomized in a 6 x 3 factorial combination (clove oil 1%, lemon grass oil 1%, basil oil 1%, rosemary oil 1%) along with control consisting of acetone 100 per cent and an insecticide spinosad 0.03 per cent with three replicates per treatment. The bioassay has been conducted by allowing the larvae to fed on maize leaves treated with essential oils and a standard check. The mortality was observed after 12, 24 and 36 hrs of application. The leaf dipping method demonstrated that clove oil (1%) showed highest mean mortality of 77.77 per cent which is the most effective among the plant oils tested next to spinosad 45 SC (0.03%) which caused 97.77 per cent mortality. The results of this experiment suggested that, clove oil was the most promising essential oil to control Spodoptera frugiperda third instar larvae.