Pacific Pests, Pathogens and Weeds

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Summary

• Widespread. Asia, Africa, North, South, Central America, the Caribbean, Europe, Oceania. In Australia, Fiji, French Polynesia, New Caledonia, Papua New Guinea, Solomon Islands.
• Moderately serious disease of dryland rice and on wild grasses. Affects seedlings and mature leaves, sheaths and panicles. IRRI estimates 5% losses throughout Asia annually, possibly worse where soil deficiencies.
• Yellow-brown or brown spots girdling seedlings; later, spots up to 10 mm, grey centres and dark margins on mature leaves. Seeds with ‘eye-spots’ fail to fill. Spots on leaves and seeds show black fungal growth.
• Spread in wind and long distances in seed; survival in seed, volunteer rice, debris and grasses.
• Cultural control: treat seed hot water (53-54°C for 10-12 minutes); apply recommended rates of fertilizer; collect straw and burn, or plough stubble and straw into soil after harvest; resistant varieties.
• Chemical control: priority is correct nutrition and resistant varieties; seed treatment with iprodione, carbendazim, or strobilurin and azole products. Also apply treatments at tillering and booting.