Studies on the Efficacy of Cow Dung Ash against Maize Weevil, Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

Experiments were carried out to assess the protectant ability of cow dung ash (CDA) to maize grains against Sitophilus zeamais Motsch. under laboratory conditions of 28-32oC and 60-75% relative humidity (R.H.). The CDA at different doses of 0.625, 1.25, 2.50, 5.00, 10.00% (w/w) were used and permethrin powder at 0.625% used as positive control, negative control was also set up in different Petri dishes to which no permethrin or ashes were added. Five pairs of weevils were introduced into each of the Petri dishes and covered with muslin cloth. The experiment was arranged in a completely randomized design (CRD) and replicated three times. Effect of the treatments on adult mortality was determined. Adult emergence and weight losses in seeds treated with CDA at different doses were also assessed. Findings of the study revealed that the adult mortality of S. zeamais among different CDA doses differed significantly (p < 0.05) and ranged from 13.33 to 100.00% at 96 hours after treatment (HAT). Results of the study also showed that LD50 of CDA against S. zeamais at 24 hours after treatment (HAT) was 4.57 % (w/w). There were no F1 adult emergences of S. zeamais in all the treatments. Weight losses were found to differ significantly (P<0.05) which were observed in grains treated with the lowest dose and the control only. It was found that CDA had no adverse effect on the germination of maize. There is therefore the need to identify the bioactive compounds in CDA that are responsible for its insecticidal ability against S. zeamais. Key words: Adult emergence, Cow dung ash (CDA), Germination capacity, Mortality, Grain damage, Sitophilus zeamais