Efficacy of Different Doses of Pyrethrum on Maize and Bean Grain Weevils under Controlled Conditions

2.1 Abstract Grain losses from insect infestation during storage are a serious issue, especially in developing countries, and can result in significant economic losses of several billion dollars and affect food security. Maize and bean weevils are responsible for pre- and post-harvest damage to maize and beans. Currently, farmers have been encouraged to use botanical insecticides for insect pest control instead of synthetic pesticides because of the several problems associated with synthetic substances. A laboratory study was conducted at the Department of Crop Science and Horticulture Laboratory of Sokoine University of Agriculture in Morogoro, Tanzania, to determine the responses of maize and bean weevils treated with different dosages of pyrethrum and at different times of exposure under controlled conditions. Pyrethrum powder at six dosage levels (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 g/100g) was mixed with 100 g of disinfested maize and bean grains in 750 ml plastic containers, and the effect on insect mortality, grain damage, and weight loss was assessed. The results showed that there was significant difference only in the highest concentration (2.0 g/100 g and 2.5 g/100 g for bean and maize grains respectively) pyrethrumand the control (P<0.05). The powders are cheap and safer for human consumption hence is recommended to be usedas maize and bean protectants in storage. Further studies on the packaging and sales of these plant powders for easy accessibility to farmers and consumers of maize is also suggested. Keywords: Maize grains; bean grains; chemical control; pyrethrum powder; pyrethrum extracts; maize weevils; bean weevil