Persistence of insecticidal activities of crude essential oils of three aromatic plants towards four major stored product insect pests

Abstract

Essential oils of aromatic plants with insecticidal properties are more and more considered as alternative insecticides
to protect stored products. Many banned insecticides have high persistence which allow them to occur at several
levels of trophic chains. The aim of the present work is to analyse the persistence of insecticidal activity of crude
essential oil of three most used local aromatic plants : Annona senegalensis Pers. (Annonaceae), Hyptis spicigera L.
(Lamiaceae) and Lippia rugosa L. (Verbenaceae) towards the four majors stored product insect pests: Sitophilus
zeamais Motsch., Sitophilus oryzae L., Callosobruchus maculatus Fab. and Tribolium castaneum Herbst. This
research revealed that H. spicigera essential oil was the most active towards S. oryzae with a LD50 = 20.18ppm. T.
castaneum was the less sensitive insect to the three essential oils tested. During a period of 24 hours L. rugosa
essential oil was the most persistent, showing mortalities for S. zeamais of 80%, S. oryzae more than 60%, C.
maculatus 100% and T. castaneum 50%. The two other oils tested were not as persistent as L. rugosa. This important
persistence of the essential oil of L. rugosa could be explained by its high content of oxygenated compounds
compared to that of the other oils. This most interesting essential oil is therefore a suitable one for popularisation in
strategies of pest management in storage.