Potential of Light Spectra as a Control of Cowpea Weevil, Callosobruchus maculatus, Activity

Abstract

Damage of stored cowpea by the weevil, Callosobruchus maculatus, is of great concern in Nigeria. The study investigated the potential of light spectra in the control of the bean weevil; In the first trial, ten individual bean weevils were directly irradiated with green, yellow, red and white and ambient(control) light generated by electric bulbs at 25 Watts. In the second trial, ten individual weevils were housed with 700 bean seeds and exposed to the light spectra. Each light treatment was replicated thrice and weevils were exposed for two hours daily for 10days. Mortality of the bean weevils was monitored daily, and percentage bean damage was determined in 10days. Data obtained were expressed as mean (±SD);mean damaged beans were compared by analysis of variance and separated by Duncan multiple range test at p<0.05. Under direct exposure, the highest mortality rate was recorded under blue light in the first five days followed by red light. From day six to nine, the highest mortality was recorded under the white light followed by blue and red. The highest mortality was recorded under white light followed by red and blue light under indirect exposure (with beans). Percentage bean seed damage was significantly (p≤0.05) lower under white (1.38%), blue (1.53, 2.38%) and red (2.48%) lights; a significantly (p<0.05) higher bean damage was recorded under ambient light (17.81%). White, blue and red lights were lethal to beans weevil by killing them and reducing their activities.