Abstract

The effects of aqueous and oil leaf extracts of Pterocarpus santalinoides at concentrations of 5, 10, 15 and 20%v/v, each as proctectant in the control of the maize weevil, Sitophilus zeamais, were compared with a conventional insecticide, pirimiphos-methyl at a rate of 0.5 ml / 50 g maize grains of Oba Super II variety in a Completely Randomized Design with four replicates. Parameters assessed, include adult mortality, rate of oviposition and adult emergence, grain damage and weight loss, and seed viability. The data were subjected to analysis of variance and means separated by using Duncan’s Multiple Range Test. Mortality of adult S.  zeamais increased  with increased concentration of the extracts as well as with days of exposure. Emergence rate was significantly (p<0.05) reduced from 41.82% pt in the control values to 19.35 to 2.14% in P. santalinoides aqueous and 9.30 to 0.90% in P. santalinoides oil with pirimiphos methyl having the least number of emerged adults (0.60%). Damaged maize seeds varied from 12.32 to 1.98% in P. santalinoides aqueous extract and 4.86 to 0.61% in P. santalinoides oil extract while 0.59% was recorded in Pirimiphos methyl-treated seed grains. Grain weight loss significantly varied between treatments after two and a half months (F11, 24= 1499.2, p<0.0001). Highest seed germination percentage (78.60%) was observed in seeds treated with 5%v/v P. santalinoides aqueous extract and the control, followed by 72.40% in P. santalinoides oil concentrations at 5, 10 and 15%v/v.  The findings showed that almost all treatments except un-treated control decreased (weevil reproduction) grain weight loss and grain damage (holes on grains) in maize.

Key words: Pterocarpus santalinoides, pirimiphos-methyl, sitophilus zeamais, effects, grain damage and weight loss.