Northern Leaf Blight Progress and Spread from Infested Maize Residue

Local epidemics of northern leaf blight, incited by the fungus Exserohilum turcicum (Pass) Leonard & Suggs, usually originate from conidia on infested maize residue. The effect of four residue levels: 0,1,2, and 3kg/2.25m2 on the progress and spread of northern leaf blight was monitored on a susceptible maize cultivar EV8429-SR. Final percentage leaf area blighted and area under disease progress curve were significantly (P ≤ 0.05) higher in the residue infested plots compared to the residue-free plots. Disease severity decreased with increase in distance from the maize residue area, whereas the apparent infection rate remained relatively constant. Gradients of disease spread curves were significantly (P ≤ 0.01) influenced by levels of maize residue and ranged from 0.2 to 1.6. The gradients flattened as the season progressed. Presence of lesions in residue-free plots indicated background contamination and/or disease spread from the residue-infested plots