Insecticidal Activity of Garlic and Onion Essential Oils against Pseudotheraptus devastans in Coconut

Abstract

Pseudotheraptus devastans (Heteroptera: Coreidae), commonly known as the coconut bug, is a major pest of coconut palms in Côte d'Ivoire. All larval stages and adults cause damage by their bites, resulting in either deformation of young nuts or their fall. As part of the search for a strategy to protect these nuts from attack, an evaluation of the effectiveness of essential oils from Allium sativum and Allium cepa was tested on out. The study was conducted at the coconut research station of the National Centre for Agricultural Research in Côte d'Ivoire. The essential oils extracted from the two aromatic plants were tested by contact using a hand sprayer at different concentrations on the eggs, larvae and adults of P. devastans at a temperature of 26.39 ± 1.50°C and a relative humidity of 87.85 ± 2.15%. These essential oils have insecticidal properties against P. devastans. The essential oil of A. sativum had LC (50) and LC (90) values of 0.27 ± 0.6% ; 11.24 ± 0.57% for larvae and 3.82 ± 0.07% ; 11.28 ± 0.17% for adults, whereas that of A. cepa had LC (50) and LC (90) values of 0.59 ± 0.51% ; 38.16 ± 0.93% for larvae and 4.84 ± 0.10% ; 20.05 ± 0.25% for adults. The essential oil of A. sativum was therefore the most toxic.