Integrating varietal resistance with Xylopia aethiopica (Dunal) A. Richard seed extract for the management of Sitophilus zeamais Motschulsky in stored maize

In search for alternatives to synthetic pesticides in maize (Zea mays, L.) storage, an integrated weevil management scheme involving varietal resistance and Xylopia aethiopica (Dunal) A. Richard seed extract was evaluated in the laboratory. Varying rates of X. aethiopica extract were assessed on three maize varieties (Pajo White, Tsolo Yellow, and DMR-LSR-Y) with differing susceptibility to Sitophilus zeamais. The different rates of X. aethiopica extract significantly interacted with maize varietal resistance and reduced fecundity of S. zeamais and maize seed weight loss due to insect’s feeding. Treatment of seeds with extract at 1.0 ml/20 g seed caused significant (above 50%) mortality at 24 h post treatment in all varieties whereas no mortality was recorded with the control and 0.2 ml/20 g seed. DMRLSR-Y was better protected than the remaining two varieties in the integrated weevil management scheme. A repellency bioassay of the extract also revealed that the extract was strongly repellent to S. zeamais with 73% (Class IV) repellency recorded in 0.4 ml/30 cm2