Pyricularia Leaf Spot

Nisikado (1927) reported this leaf spot disease from Japan. In India, Rathaiah (1980) described the occurrence of the disease in Assam. The disease has very limited occurrence.

Symptoms

Symptoms consist of small pale brown spots on the leaves and on the rhizome node near the soil line. The freckles, bearing sclerotium-like structures, sometimes coalesce to form black blotches. Black blotches are also seen on the rhizomes, which may extend into the cortex. The pathogen also causes leaf blast symptoms. The blast lesions occur during July to September (Kotani and Kurata, 1992).

The Pathogen

Nisikado (1927) named the pathogen Pyricularia zingiberi. Rathaiah (1980) isolated the causal fungus from ginger leaves in Assam. In Tanzania, Teri and Keswani (1985) reported a new species of Pyricularia occurring on ginger and called it P. grisea. Sadasivam and Subramanian (1954) found Pyricularia zingiberi to be heterotrophic for thiamine.

P. zingiberi overwinters with sclerotium-like structures on the residues of diseased ginger and mioga (Zingiber mioga) plants. The source of primary infection for ginger plants appears to be the debris of diseased plants (Kotani, 1994).

Control Measures

Chemical Control: The disease can be controlled by applying Dithane M-45 in combination with Benlate (Anonymous, 1977). Treatments with Dithane M-45 followed by a mixture of mancozeb and Topsin-M also gave best control of the disease and an increase in the yield of ginger rhizomes (Anonymous, 1980). Kotani (1994) suggested soil fumigation with methyl bromide to kill the overwintering sclerotium-like structure.

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