Vol. 1, Issue 4 (2016)
Bioefficacy of Zingiber officinale against Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae) infesting cowpea
Author(s): Ogbonna Confidence U, Okonkwo Nnaemeka J, Nwankwo Edith N, Okeke Peter C, Ebi Sowechi E
Abstract: Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae) is an important primary insect pest of cowpea in the store causing considerable damage to the grains. In this study, the bio-activities of Zingiber officinale rhizome (Ginger) powder and oil extract were investigated against C. maculatus. The powders of Z. officinale rhizome was screened in the laboratory against adult C. maculatus at different proportions (25%, 20%, 15%, 10% and 5% wt/wt) with Actellic dust insecticide as a reference insecticide. The highest proportion (25% wt/wt) of Z. officinale powder was shown to be the most effective, and significantly reducing the survival of C. maculatus to 0% after 12 days of treatment. The oil extract of Z. officinale at different concentrations (700, 350, 175, 87.5 and 44 µL/mL) and Agricombi insecticide (which is a combination of Fenitrothion (30%) and Fenvalerate (10%)) as the reference was equally evaluated for the following: contact toxicity on adult insect by dipping, residual effect, repellency effect, effect on adult emergence in treated grains and damage to grains. Percentage survival of the insects was significantly reduced at higher concentration of the extracts. There was no survival (0%) recorded at 700 µL/mL of Z. officinale oil in dipping and in residual toxicity. Grains treated with the different concentrations of Z. officinale oil extracts significantly repelled insects with the highest concentration of 700 µL/mL yielding 100% repellency to C. maculatus. The least mean adult emergence of 0.0 was recorded for both 700 µL/mL and 350 µL/mL of the oil extract used against C. maculatus. Grains treated with the plant powder and oil extract significantly (P<0.05) reduced damage caused by C. maculatus as compared to the untreated grains and gave a better protection to the grains compared to Agricombi insecticide. The present studies therefore indicate that Z. officinale powder and oil extracts showed promise in the control of C. maculatus in stored cowpea.