Grey leaf spot (GLS) caused byCercospora zeae-maydisTehon and Daniels has become the most important foliar disease of maize in South Africa. Crop rotation has been applied successfully to control or reduce the incidence and severity of plant diseases in general. GLS severity in maize monoculture and maize rotated with soybeans was monitored over four growing seasons. To reduce interplot effects experimental plots were surrounded by buffer rows of a resistant maize cultivar which was sprayed with fungicides every two weeks. Percentage GLS severity was visually assessed at fortnightly intervals. No significant differences in grey leaf spot severity were found between maize grown in monoculture or when rotated with soybeans. This result may be attributed to the ability of grey leaf spot spores to survive for two years in maize debris on the soil surface. It appears, therefore, that short term crop rotation will not control the disease under epidemic conditions.
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