Oil extracts from three tropical plants; Annona muricata, Moringa oleifera and Senna alata commonly used medicinally in treating various ailments were tested in the Laboratory under constant conditions at 30 + 2o C and 60-65 % relative humidity for their ability to protect local and polished rice grains against Sitophilus oryzae, a major pest in storage. Doses at 0.0, 0.5 and 1.0 ml per 100 g rice grains were separately applied for assessment of adult mortality in the laboratory for three (3) days. Parameters assessed were; single effect, combined effects and combined cumulative effects of plant oils on mortality of S. oryzae on local and polished rice. The experiment was laid out in a Completely Randomized Design (CRD) with each treatment replicated four times. The results showed that A. muricata at 1.0 ml and M. oleifera at 0.5 and 1.0 ml each recorded higher (P < 0.01) adult weevil mortality at 48 and 72 hours, respectively. In the polished rice, there were highly significant (P < 0.05) differences at 24, 48 and 72 hours where M. oleifera and S. alata at 0.5 ml each recorded higher mortalities of adult S. oryzae. The combined analysis of local and polished rice showed that the local ric was not significantly different (P > 0.01) from the polished rice among the plant oil treatments on adult weevil mortality within the period (24, 48 and 72 hours). The study also revealed that the treated local rice showed better resistance to weevil attack than the polished brand, and that the experimental plant oils could offer effective protection against S. oryzae to reduce dependency on toxic chemicals.
Keywords: Plant Oils, Sitophilus oryzae, Mortality, Annona muricata, Moringa oleifera, Senna alata