EVALUATION OF OCIMUM-KENYENSE (AYOBANGIRA) AS SOURCE OF REPELLENTS, TOXICANTS AND PROTECTANTS IN STORAGE AGAINST 3 MAJOR STORED-PRODUCT INSECT PESTS

The bioactivity of materials derived from the leaves and succulent ste ms of Ocimum kenyense against Sitophilus zeamais (Mots.), Rhyzopertha dominica (Fab.) and Sitotroga cerealella (Oliv.) was assessed in maize and sorghum grains in the laboratory. O. kenyense applied as dry or g round leaves was not toxic to S. zeamais and R. dominica. The highest dosage of essential oil killed only 35% of the weevil but induced 96% mortality in the borer after 96 h. S. cerealella was most susceptible to O. kenyense since all the plant materials bioassayed evoked higher mortalities in the moth. Grains treated with 30 g of ground leaves and 750 mg of essential oil killed all the moths after 24 h. Similarly, d ry and ground leaves had no effect on progeny production by S. zeamais but grains treated with essential oil extract significantly reduced t he number of progeny produced by the weevil. All levels of dry leaves, ground leaves and essential oil extract of O. kenyense caused signifi cant reduction in progeny produced by R. dominica and S. cerealella. T here was no progeny produced by both species in grains treated with th e highest dosages of 30 g of ground leaves and 750 mg of essential oil extract. All the plant materials were highly repellent to S. zeamais, with the highest dosages of ground leaves and essential oil evoking t he highest repellent action. The materials, however, showed only moder ate repellency against R. dominica and rather low repellency against t he moth. Ground leaves and essential oil extract provided the greatest protection of maize and sorghum against feeding by R. dominica and S. cerealella with no observable feeding damage to grains treated the hi ghest dosages of both materials. The potential practical use of O. ken ?tense as grain protectants in farm-stored grains in rural communities in Africa is discussed.