Abstract

Sitophilus zeamais (maize weevil) is a field and storage pest of maize of economic importance in several parts of Africa. Controlling of the pest by use of synthetic pesticides is raising serious concern on the environmental safety and consumer health hazards. A laboratory experiment was done to assess three botanicals, Eucalyptus terreticonis, Tagetes minuta and Lantana camara, in controlling the S. zeamais. A Completely Randomised Design (CRD) with three application rates (5g/200 g grain, 10g/200g grain and 20g/200g grain) of the botanicals replicated three times was used in the assessment. A synthetic chemical (pirimiphos-methyl) was used as a control pesticide to compare the efficacy of the botanicals on the maize weevil. The results showed higher weevil mortality and lower grain loss in the pirimiphos-methyl than in the botanicals (P< 0.05). The botanicals had significant difference on weevil mortality rates where the Eucalyptus terreticornis recorded highest mortalities followed by Tagetes minuta and Lantana camara at 20g/200 grain application rates respectively. The efficacy of the botanicals significantly (P< 0.05) decreased with time after application of the botanical powder. The Eucalyptus terreticornis at 20g/200g grain showed potential in controlling the S. zeamais and therefore may be used to protect maize grain damage from the weevil during storage. However, with a constant re-application of the botanical powder is necessary in order to maintain the efficacy at high levels.

Keywords: Botanicals; Efficacy; Synthetic pesticide; Pest; Maize

Abbreviations: CRD: Completely Randomised Design; OPMVs: Open Pollinated Maize Varieties; ARDA: Agricultural Rural Development Authority; OPv: Open Pollinated varieties