Salvaging Egg Infested Cowpea Vigna unguiculata (L.) Walp. Grains from Callosobruchus maculatus (F) (Coleoptera: Chrysomelidae) Total Damage by Exposure to Sun in Sudan Savanna Maiduguri, Nigeria

Abstract

The effect of sun exposure to eggs laid by C. maculatus on cowpea grains was conducted on four cowpea varieties Borno brown, Kanannado, Gwalam and Banjara. Ten grams’ grains of each variety were weighed into a 200 ml glass jar in three replicates for four levels of treatments. Grains were infested with three pairs of sexed male and female adult C. maculatus (1-2 days old), they were left for 5days to lay eggs and afterward removed. Number of eggs laid on grains was counted and records taken. Egg infested cowpea grains of each variety were transferred into perforated 200 ml tin containers and exposed to the sun for10, 20, and 30hours respectively while the check (control) was left on the Laboratory shelf under ambient temperature and relative humidity conditions without exposure to the sun. After the solar exposure, all treatments were returned to the shelf. Number of adults that emerged from grains in each replicate during F1 generation was counted, while percentage and severity of grain damage were calculated. Both initial and final grain moisture content were also determined. Data on all variables were computed and subjected to Analysis of variance (ANOVA) Using Statistix v10.0 significantly different means were separated using Tukey Honestly Significant Difference (HSD) at 5% level of probability. The result showed that cowpea grains riddled with C. maculatus eggs (1-5 days old) exposed to solar radiation for 10, 20 and 30 hours could be prevented from further deterioration and damage; as it reduces or completely inhibited adult emergence. Solar exposure of cowpea grains could therefore be cost effectively employed by farmers as a management strategy against the cowpea bruchid, at least in Sudan Savanna Agro-ecological zone of Nigeria under which the experiment was conducted.