Plant oils as potentiation agents of monoterpenes for protection of storedgrains against damage by stored product beetle pests

Plant oils (coconut, sunflower, sesame and mustard) at 10 and 5 ml/kg were tested alone and in combination with 1,8 cineole, eugenol or camphor at 0.5 , 1.0 and 5.0 mu l or mg/kg against Sitophilus granarius (L.), S. zeamais ( Mots.), Tribolium castaneum (Herbst) and Prostephanus truncatus (Horn) in w heat and maize-treated grains stored for 3 h or 10, 30, 60 and 90 days. All treatments with either plant oils alone or in combination with each chemic al caused significant mortality compared with untreated grain. Plant oils w hen used alone were less effective against the beetles than oils combined w ith either 1,8 cineole, eugenol or camphor. Mortality significantly decreas ed with the time after application except in treatments combining plant oil s and chemicals, which achieved complete control of all beetles exposed aft er 90 days storage following application. Treatments with plant oils and ea ch chemical either alone or in combination inhibited progeny production by S. granarius, S. zeamais and P. truncatus, irrespective of dosage used or o f storage interval following application.