Prolonged Heavy Rain Triggers Rice Blast Symptoms in Taitung Fields

Days of heavy rain have brought scattered signs of rice blast to parts of Chishang Township in Taiwan’s Taitung County, according to the Taitung District Agricultural Research and Extension Station.

Most rice in the county remains at the seedling stage, while some fields have begun tillering. Rain linked to a typhoon and tropical depression has left fields highly humid, creating conditions in which the disease could spread quickly.

Rice blast, also known as rice blight, is a major rice disease associated with temperature, humidity and fertilizer management. Rain splashing across fields can speed the movement of fungal spores and help them enter plants. Sudden temperature changes can also weaken rice plants. Excessive nitrogen fertilizer before or after rain may produce soft, overgrown leaves that are less resistant.

Early symptoms appear as dark or gray-green spots on leaves. These can expand into spindle-shaped lesions with gray-white centers, reddish-brown edges and yellow halos. If lesions merge, leaves can wither, affecting early tillering and raising the risk of panicle blast later in the season.

The station advised farmers to drain fields quickly after rain and maintain ventilation and sunlight. It also recommended avoiding excessive nitrogen fertilizer and using moderate potassium fertilizer to strengthen plants. It provided several pesticide options depending on whether symptoms had appeared, while urging farmers to inspect fields and act promptly.