Wheat Diseases and Pests - Wheat Doctor - CIMMYT

Alternaria Leaf Blight
Alternaria triticina
Symptoms: Small, chlorotic, oval- or elliptical-
shaped lesions appear and, as they enlarge, these
lesions become irregular in shape. The chlorotic
borders of the lesions may become diffuse and
turn light to dark brown in color (24). Lesions are
difficult to distinguish from those caused by
Helrninthosporiurn spp. Infection usually starts on
the lower leaves, but symptoms can be found on
all plant parts.
Development: The fungus survives as conidia on
seed or as mycelia within seed. Sporulation on
lower leaves provides inoculum that can be
dispersed by wind, leading to secondary spread of
the disease. Seed-borne inoculum often results in
spike infections late in the crop cycle. High
humidity or irrigation, as well as warmer
temperatures (20' to 25'C) favor infection and
disease development.
HostslDistribution: Bread wheat and durum wheat,
as well as several related grasses, are the primary
hosts. The disease is common in the eastern and
central areas of the Asian Subcontinent.
Importance: Alternaria leaf blight can be very
severe if environmental conditions are favorable
for disease development; major losses can result
when susceptible cultivars are grown.