Efficiency of Indian borage essential oil against cowpea bruchids

Abstract

© Int. J. of GEOMATE. Cowpea bruchids is one of the most important insect pests in stored products, especially of whole grains used for breeding or consumption. Currently, synthetic insecticides cause adverse effects to human health and the environment, thus new alternative biopesticides from herb or plant are needed for cowpea bruchids control. The aim of this research was to evaluate insecticidal activities of essential oil from Indian borage, Plectranthus amboinicus. Efficacy of this essential oil against C. maculatus was investigated by impregnated filter paper and vapor-phase tests. Experiments were conducted under Completely Randomized Design (CRD) with 4 replications. Contact activity was considered on essential oil at 6 concentrations of 0 300 600 900 1,200 and 1,500 ppm and fumigant activity was performed at 6 concentrations including 0 3 6 9 12 and 15 μL/L air. All experiments were assessed under laboratory conditions (30±2°C, 70-80%RH and 16L:8D photoperiods). Data of deaths cowpea bruchids were recorded after treated at 24 to 168 h. Contact activity showed 1,200 ppm of P. amboinicus essential oil at 168 h was the best performance in the contact toxicity on cowpea bruchids and fumigation activity presented 12 μL/L air of P. amboinicus essential oil at 72 h had the highest effectiveness in the fumigation toxicity on cowpea bruchids, with 100% adult mortality. The data pointed that P. amboinicus essential oil showed the high potential for insecticidal activity for cowpea bruchids control. Hence, the essential oil of P. amboinicus might be used as an alternative for grain protection against stored-product insects.