Narrow Brown
Leaf Spot (fungus - Cercospora janseana): The disease varies in severity
from year to year and usually becomes most severe as rice approaches maturity,
causing premature ripening and yield reduction. Leaf spots are long (1/10 to 1/2
inch), narrow (1/32 inch), and cinnamon-brown. Premature leaf death will occur
in severe cases. Late in the growing season, the fungus often attacks the sheath
of the flag leaf causing the "brown blotch" or "net blotch" phase of the disease
in which a large (1 1/2 to 3 inch long) cinnamon brown lesion is formed and typically
encircles the uppermost internode about an inch below the the base of the panicle.
Early maturing varieties tend to escape the major impact of the disease. There
are differences in suseptibility among some rice varieties, however, due to buildup
of certain races of the fungus, resistance does not remain reliable. Some foliar
fungicides effectively suppress this disease and may be economical if other diseases
are also controlled along with the narrow brown leaf spot.
