Development-inhibiting activity of some tropical plants against Sitophiluszeamais Motschulsky (Coleoptera : Curculionidae)

Thirteen tropical plants were evaluated for development-inhibiting activity against Sitophilus zeamais. The bioassays were carried out by incorporatin g seeds or leaves at various dose levels into an artificial diet for the te st insect. It was found that seeds of Basella alba and leaves of Operculina turpethum and Calotropis gigantea were potent in delaying development and in reducing adult emergence, and hence the capacity for population increase . At 0.5% concentration, adult emergence in tests with B. alba, O. turpethu m and C. gigantea was reduced by 62, 95 and 70%, respectively. In B. alba a nd C. gigantea, the development periods were 2.2 and 1.8 times those in the control and the capacities for increase/day were only 0.0324 and 0.0328 co mpared with 0.1004 in the control. B. alba, O. turpethum and C. gigantea we re active at concentrations as low as 0.01, 0.05 and 0.1%. The potential of these materials in insect pest management is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.