Evaluation of feeding deterrents of Tephrosia Vogelii Hook and Calodendrum capense Thunb dusts against Prostephanus truncatus Horn in grain storage

Abstract

Biossay experiments were conducted both in the laboratory and in storage to evaluate efficacy and repellent properties of two botanicals; Tephrosia vogelii Hook and Calodendrum capense Thunb dust at the rate of 0.11%, w/w and 0.22% w/w as feeding deterrents against shelled hybrid 5HB maize weevil, Prostephanus truncatus Horn. Their efficacies were compared with standard actellic super (2% dust 0.056% w/w). T. vogelii, C. capense and actellic super dust attained mean mortalities of 60%, 70% and 100% respectively on adults of P. truncatus over exposure period of 28 days .The lethal mean mortality exposure time (LT50) varied from 8-14 days for the two botanicals. The two botanicals and actellic super effectively reduced the F1 progeny by more than 60%. The former products exhibited a higher repellency against P. truncatus at lower dosages (0.11%w/w) compared to actellic super dust. The three treatments offered effective protection of shelled maize grain for the first 90 days. However, significant (P=0.05) percent weight loss was observed there after, hence requiring a repeat application after the initial 3 months.