Chemical Composition of Cupressus Lusitanica and Eucalyptus Salignaleaf Essential Oils and Bioactivity against Major Insect Pests of Storedfood Grains

Abstract

tThe leaf essential oils from Cupressus lusitanica, Miller and Eucalyptus saligna, Smith obtained by hydrodis-tillation were analyzed by GC/MS and also screened for their insecticidal and repellent effects against adultTribolium castaneum, Acanthoscelides obtectus, Sitotroga cerealella and Sitophilus zeamais. The C. lusitanicaoil contained mainly umbellulone (18.38%) and -pinene (9.97%) whereas the E. saligna oil was domi-nated by -pinene (24.40%) and 1,8-cineole (24.26%). Bioassays showed that of the four insect speciestested, A. obtectus and S. cerealella were the most susceptible to the oils, with LC50values of 0.05–0.11%v/w in contact toxicity and 4.07–7.02 l/L air in space fumigation. Except in T. castaneum with percentagerepellence (PR) values of 65–92.5%, the other test insects recorded PR values less than 30%. The PR valuesdecreased with exposure time in all insects except in T. castaneum. Our results show that C. lusitanica andE. saligna essential oils are promising insecticides and repellents to be used against insect pests of storedfood grains.