Damage Pattern
Small brownish spots appear on the leaves, typically not systemically arranged but limited by the leaf veins. Over time, the number and concentration of these spots increase, expanding beyond the veins. The centre of the spot becomes light brown and is surrounded by a reddish-brown ring, with a yellow halo separating the spot from healthy green tissue. This appearance gives the disease its name. If the disease is widespread, leaf sheaths and bracts can also be affected, and the leaves die prematurely.
Biology
The conidia overwinter on maize residues. Rain and wind can spread the conidia to young plants in spring, leading to leaf spot development. Cool, humid conditions (10-12°C) favour the disease's spread. Infection begins on older leaves and progresses upward through the plant as the season advances.
Control
To reduce the risk, maize residues should be thoroughly incorporated after harvest. Using less susceptible varieties and improving crop rotation planning by taking breaks from maize cultivation can also help prevent the disease.