BIOEFFICACY OF ZINGIBER OFFICINALE AGAINST PROSTEPHANUS TRUNCATUS HORN (COLEOPTERA: BOSTRICHIDAE) INFESTING MAIZE.

Abstract

ABSTRACT Maize is an important cereal crop grown in sub-Saharan Africa however, greater part of the grains produced is destroyed in storage by Prostephanus truncatus Horn (Coleoptera: Bostrichidae). In this study, the bio-activities of Zingiber officinale rhizome (Ginger), was investigated in the laboratory against P. truncatus at different proportions (25%, 20%, 15%, 10% and 5% wt/wt) with Actellic dust insecticide as a reference insecticide. The highest proportions (25% wt/wt) of Z. officinale powder significantly reduced the survival of P. truncatus to 0% after 12 days of treatment and the LD50 of the dust was obtained as 6.72%. The oil extract of Z. officinale at different concentrations (700 µL/mL, 350 µL/mL, 175 µL/mL, 87.5 µL/mL and 44 µL/mL) and Agricombi insecticide as the reference was equally evaluated for the following: contact toxicity on adult insect by dipping, grain residual treatment, repellency effect, effect on progeny and adult emergence in treated grains and damage assessment to grains. There was no survival (0%) recorded at 700 µL/mL both in contact and residual treatment of P. truncatus. The LD50 of the oil extract was obtained as 84.78 µL/mL. Grains treated with the different concentrations of Z. officinale oil significantly repelled insects with the highest concentration of 700 µL/mL yielding 100% repellency. The least mean adult emergence of 0.0 was recorded for both concentrations of 700 µL/mL and 350 µL/mL in treated grains. Grain damage by P. truncatus was significantly reduced when treated with Powder and oil extract of Z. officinale compared to the untreated grains.