WHEAT – LOOSE SMUT:
It is a seed borne disease; infection occurs during Loose Smut flowering through wind-borne spores.
The infection remains dormant inside the otherwise healthy looking seed but the plants grown from such seeds bear infected inflorescence.
At this time, infected heads emerge earlier than normal heads. The entire inflorescence is commonly affected and appears as a mass of olive-black spores, initially covered by a thin gray membrane.
Once the membrane ruptures, the head appears powdery.
SURVIAL AND SPREAD
The disease is internally seed borne, where pathogen infects the embryo in the seed.
Primary infection occurs by sowing infected seeds.
Infection is favored by cool, humid conditions during flowering period of the host plant.
- Use clean seed: Apply systemic fungicide treatment of seeds. Contact fungicides are not effective.
- Use resistant cultivars.
- Perform field checks for infected seed and prevent the use of seeds from infected fields for further cropping.
The most common site for symptoms is on upper leaf blades, however, sheaths, glumes and awns may occasionally become infected and exhibit symptoms.
The pustules are circular or slightly elliptical, smaller than those of stem rust, usually do not coalesce, and contain masses of orange to orange-brown Urediospores.
Survival and spread
Pathogen over-summers in low and mid altitudes of Himalayas and Nilgiris. Primary infections develop from wind deposited urediospores in eastern Indo-gangetic plains in middle of January where it multiplies and moves westwards by March
Alternate host is Thalictrum sp.
Temperatures of 20-25° C with free moisture (rain or dew) cause epidemics. Severe infection causes up to 30 percent yield losses.