Peronosclerospora spontanea (spontaneum downy mildew)

On young leaves, pale yellow to white streaks or stripes of various lengths appear, extending from the leaf bases to the leaf tips. Older leaves show continuous or interrupted yellowish streaks along the blades. With age, the streaks elongate, coalesce with adjacent streaks and turn reddish-brown. Leaf twisting and yellowish streaks are observed on some plants. Conidia may be produced in the streaks under suitable conditions. Ultimately, leaf shredding occurs from the disintegration of mesophyll tissue beginning at the leaf tips. The shredded tissue contains numerous oospores, which scatter readily in the wind.

Plant quarantine measures and the use of resistant varieties are important for the control of the disease.

In the Philippines, yield losses due to this disease are directly related to the resistance of the sugarcane variety grown. The disease is not economically important in Thailand.