Assessment of grain protection through the incorporation of Eucalyptus citriodora leaves in grain/insecticide admixtures in Zimbabwe

Purpose: The control of stored-grain insect pests is predominantly done through the use of synthetic insecticides. However, the extensive and constant (mis)use of these chemicals has brought complications that include faster evolution of resistant forms of pests, hence a global call for alternative control measures to reduce chemical applications.  The aim of this research was to evaluate the repellent and toxic effects of E. citriodora leaf powder on adult P. truncatus and Sitophilus zeamais. Research Method: A completely randomized design was adopted in all the experiments. A choice test arena was set up to evaluate repellent effects of E. citriodora leaf powder on P. truncatus and S. zeamais. The toxic effect of E. citriodora was also evaluated, with untreated grain and conventional insecticides used as negative and positive controls, respectively. Findings: Results showed that E. citriodora leaf powder had repellent properties of up to 68.9% against both P. truncatus and S. zeamais populations. Nonetheless, low adult P. truncatus mortalities were recorded when the protective effects of the E. citriodora leaf powder (at the rate of 10% w/w) were tested against the beetle. Additionally, the efficacy of the synthetic insecticides was relatively higher when applied singly than when in combination with E. citriodora leaf powder. Research limitations: Time was the major limiting factor to consider other parts of E. citriodora plant (e.g. roots) on their usefulness in stored-product insect pest management. Originality/Value: Small plantations of E. citriodora may be established to offer a temporary grain protection against primary insect pests.