False Smut
(Ustilaginoidea virens)

• Individual rice grain transformed into a mass of yellow fruiting bodies
• Growth of velvetty spores that enclose floral parts
• Infected grain has greenish smut balls with a velvetty appearance.
• The smut ball appears small at first and grows gradually up to the size of 1 cm.
• It is seen in between the hulls and encloses the floral parts.
• Only few grains in a panicle are usually infected and the rest are normal.
• As the fungi growth intensifies, the smut ball bursts and becomes orange then later yellowish-green or greenish-black in color.
• Infection usually occurs during the reproductive and ripening stages, infecting a few grains in the panicle and leaving the rest healthy.

• Chlamydospore formed on the spore balls are born laterally on minute sterigmata on radial hyphae, and are spherical to elliptical, warty, olivaceous, 3-5 x 4-6 µm. Younger spores are smaller, paler, and almost smooth.
• Some of the green spore balls develop one to four sclerotia in the center. These sclerotia overwinter in the field and produce stalked stromata the following summer or autumn.
• In temperate regions, the fungus survives the winter by means of sclerotia as well as chlamydospores.
• It is believed that the primary infections are initiated mainly by the ascospores produced from the sclerotia.
•  Chlamydospores play an important role in secondary infection, which is a major part of the disease cycle.

Conditions that favour disease development

• presence of rain and high humidity
• presence of soils with high nitrogen content
• presence of wind for dissemination of the spores from plant to plant
• presence of overwintering fungus as sclerotia and chlamydospores
• flowering stage of the rice crop

• Use of disease-free seeds that are selected from healthy crop.
• Seed treatment with carbendazim 2.0g/kg of seeds.
• Control insect pests.
• Split application of nitrogen is recommended.
• Removal and proper disposal of infected plant debris.

• Among the cultural control, destruction of straw and stubble from infected plants is recommended to reduce the disease.
• Use varieties that are found to be resistant or tolerant against the disease in India.
• Avoid field activities when the plants are wet.
• Early planted crop has less smut balls than the late planted crop.
• At the time of harvesting, diseased plants should be removed and destroyed so that sclerotia do not fall in the field. This will reduce primary inoculum for the next crop.
•  Field bunds and irrigation channels should be kept clean to eliminate alternate hosts.
• Excess application of nitrogenous fertilizer should be avoided.
• Regular monitoring of disease incidence during rabi season is very essential.
• Proper Destruction of straw and stubble.

• Spraying of copper oxychloride at 2.5 g/litre or Propiconazole at 1.0 ml/litre at boot leaf and milky stages will be more useful to prevent the fungal infection.
• Seed treatment with carbendazim 2.0g/kg of seeds.
• At tillering and preflowering stages, spray Hexaconazole @ 1ml/lit or Chlorothalonil 2g/lit.
• In areas where the disease may cause yield loss, applying captan, captafol, fentin hydroxide, and mancozeb can be inhibited conidial germination.
• At tillering and preflowering stages, spraying of carbendazim fungicide and copper base fungicide can effectively control the disease.