Efficacy of mixed powders of <i>Piper guineense</i> and <i>Zingiber officinale</i> as maize grain protectants against <i>Sitophilus zeamais</i> Motschulsky (Coleoptera: Curculionidae)

Abstract

This study was carried out to evaluate the effects of mixed powders of Piper guineense (Piperaceae) and Zingiber officinale (Zingiberaceae) on Sitophilus zeamais population and seed weight loss percentage of stored maize. Experiment was conducted under laboratory conditions (26.94 ± 0.81 °C, 74.76 ± 4.51% r.h. and 12 h photoperiod). In a completely randomized design with three replications, powders of P. guineense and Z. officinale were applied separately and in mixtures at the ratios of Zg100%:Pg0% (T1), Zg0%:Pg100% (T2), Zg30%:Pg70% (T3), Zg70%:Pg30% (T4) and Zg50%:Pg50% (T5), respectively. The mortality rate of S. zeamais adults was recorded and compared with the control at 24, 48, 72, 96, 120 and 168 hours after treatment. Maize grain damage and seed weight loss percentage were determined. Results showed highly significant differences with S. zeamais mortality rate between treatments, treatment exposure duration and their interactions (p<0.001). P. guineense, alone, showed the best efficacy (mortality rate = 96.66 ± 5.77% at 96 hours after treatment) and mixed with Z. officinale at the ratio 70%Pg: 30Zo (mortality rate = 93.33 ± 5.77%). Taking into account this high performance of P. guineense seed powder, it can be recommended as stored maize grain protectants.

Keywords: Botanical insecticides, maize storage, Sitophilus zeamais, weight loss, mortality rate.