Overview

The study was carried out to establish the microflora causing maize ear rots in the field; the level of mycotoxins and to determine the reaction of commercial maize varieties against F. moniliforme and S. maydis, the two most common causative agents of maize ear rots. Maize samples were collected from major maize growing districts of Uganda at harvest. The kernels were plated onto malt salt agar for mould growth and mycotoxin analysis was carried out on the same samples. Species of Fusarium, Aspergillus, Penicillium, Acrimonium, Phomopsis and Rhizopus were identified. Fusarium spp and Aspergillus spp were the most common moulds, with Fusarium moniliforme being the most prevalent species isolated from most of the plated kernels. The mean aflatoxin levels in the ‘healthy’ kernels ranged from 0.6 to13.5 ppb while in infected kernels it ranged from 2.7 to 35 ppb. The twenty commercial varieties were inoculated at silking stage with Stenocarpella maydis and Fusarium moniliforme using infected toothpicks at Namulonge in central Uganda, Kamenyamigo in Masaka, and Kere in Kapchorwa to determine the reaction in different environments. S. maydis resulted in higher percentage ear rot than F. moniliforme at Namulonge and Kamenyamigo but at Kere, F. moniliforme was more severe. The implications of the results are that a) a large number of fungal pathogens are responsible for causing maize ear rots, b) tolerance of maize genotypes to maize ear rots varies with season and location, c) aflatoxin levels vary with season and sometimes exceed acceptable limits.