The symptoms associated with leaf scald vary according to the stage of growth, variety and plant density. In most cases, grey-green, water-soaked lesions start to develop on the tips or edges of leaf. Later, the lesions spread and produce a zonate pattern of alternating light tan and dark brown starting from the leaf tips or the edges. The continuous enlargement of lesions result in blighting of a large part of the leaf blade. The affected areas dry out, giving the leaf a scalded appearance. In some countries, lesions rarely develop the zonate pattern and only the scalding symptom is evident.
Disease development usually occurs late in the season on mature leaves and is favored by wet weather, high nitrogen fertilization, and close spacing. Rates of nitrogen above 40 kg/ha and above result in a greater incidence of leaf scald. It develops faster in wounded than in unwounded leaves. The sources of infection are seeds and crop stubbles from previous harvest. To differentiate leaf scald from leaf blight, immerse cut leaves in clear water for 5−10 minutes; if no ooze comes out, then it is leaf scald.
No alternative treatment has been found so far against this disease.
Always consider an integrated approach with preventive measures together with biological treatments if available. The use of thiophanate-methyl in a seed-soak treatment reduced infection by M. albescens. In the field, foliar sprays with fungicides based on mancozeb and copper oxychloride significantly reduce the incidence and severity of leaf scald. Combinations of these chemicals were also effective.
When available, use resistant varieties.,Make the spacing between plants somewhat wider.,The maintenance of silicon levels in soil also results in higher yields and a reduction of disease.,Avoid excessively high rates of nitrogen.,Split applications of nitrogen during the tillering stage.,Remove weeds and infected rice plants from the field.