Vol. 2, Issue 5, Part F (2016)

Abstract
Chemical insecticides are mixed with maize grains to offer protection against insect pest infestation during storage period. The insecticides are deposited onto the surface of the maize grains preventing possible insect pests from crawling and burrowing the maize grains and therefore causing damage. Chemical insecticide residues have raised environmental and food safety concerns on the possible adverse effects they may induce. Research studies have been done on alternative insect control methods including ethnobotanicals. Pyrethrum plant powder containing pyrethrins used since antiquity for formulation of household insecticides was assessed. Pyrethrins are unstable on light exposure and increased temperatures and suitable mostly for indoor applications. In the current study, pyrethrins in incremental ratios were assessed for initial deposition onto maize grains and residue levels over a six-month period at 28 ± 2 ºC and 65 ± 5% RH storage conditions. The pyrethrins in the powder were standardized at 1%^w/_w. Monitoring of residue levels provided an indication of unstabilized pyrethrins’ ability to protect maize grains against insect pest infestation. Initial deposition was determined on treatment day (24hrs). Residue levels were determined at 90^th and 180^th day after application. Initial pyrethrins deposition onto maize grains was quantified using HPLC and compared with pyrethrins quantity before application using chi square (χ²). Results showed that initial deposited pyrethrins onto the maize grains showed no significant difference with the quantity of pyrethrins before application. Residue levels at three and six month showed that pyrethrins degraded in large proportion over this period. Milled grains still showed residue levels although at lower quantities indicating further degradation on milling process. Based on this study it is recommended that unstabilized pyrethrins be utilized as grain storage protectant.