An investigation into the potential use of premna corymbosa as insect repellent

The potential insect repellent properties of Premna corymbosa was investigated. Plant extracts from the leaves, stems and roots were prepared in an aqueous and ethanolic solution for tests against three common insect pests namely, cockroaches, houseflies and mosquitoes for repellency. The cockroaches were Periplaneta americana, mosquitoes were Aedes aegypti and housflies were Musca domestica. All forms of the extracts showed repellency in varying degrees against adult cockroaches. The highest repellent of 40% observed was the root ethanolic extract in the powder form and this repellency fall short of the minimum 60% repellence required. The lowest was also from the roots of Premna whose water extract in aqueous form was only about 24.45 %. It showed that ethanolic extract only improved the repellency but not adequate to qualify as a potential repellent for cockroaches. No mortality was observed during the test period. Repellencies were expressed in varying degrees against adult houseflies and the values were less than 40. The highest was from the ethanolic extract in powdered form obtained from the roots, which was 33.33. The lowest repellency was obtained from the water extract in aqueous forms obtained from leaves and roots giving index values of 14.29. From the results obtained, it can be seen that all of the extract forms, either in solvent or powdered forms, showed some minimal repellency towards mosquitoes. The plant extract which gave the highest protection was from the stem ethanolic extract in aqueous form, which is 60.72. The lowest protection was found to be from leaf water extract in the powdered which was 14.29. There was no significant difference between the various forms either these were prepared from stems, roots or leaves of P. corymbosa. It possesses a low repellent property which is not significant enough for it to act as a pest repellent towards cockroaches, houseflies and mosquitoes.