Evaluation of Ocimum suave (Willd) as a source of repellents, toxicants and protectants in storage against three stored product insect pests

The bioactivity of materials from the leaves and succulent stems of O. suave was tested against Sitophilus zeamais (Mots.), Rhyzopertha dominica (Fab.) and Sitotroga cerealella (Oliv.) in maize and sorghum. O. suave applied as dry or ground leaves was not toxic to S. zeamais but as essential oil extract was highly toxic to the weevil. Higher dosages of ground leaves and essential oil extract induced 100% mortality in R. dominica. S. cerealella was most susceptible to O. suave since all the plant materials bioassayed evoked higher mortalities in the moth. The materials also caused significant reduction in progeny produced by the insects. All the plant materials were highly repellent to S. zeamais, with ground leaves evoking the highest repellent action. There was, however, considerable variation in the repellency of the materials against R. dominica and S. cerealella. Ground leaves and essential oil extract provided the greatest protection of maize and sorghum against attack by the insects. The potential practical use of O. suave as grain protectants in farm-stored grains in rural communities in Africa is discussed.