Plant Pathology Prof.(Dr.) Punam Jeswal Head B.Sc (Hons.) Part l Botany Department
Loose smut of wheat is distributed worldwide but it is a serious in the humid and semi-humid wheat growing areas.
SYMPTOMS - 1. The disease manifests itself when the plants are in ears. Diseased ears emerge out of the boot leaf a little earlier than the healthy ones and a black powdery mass of spores replace the flowers.
2. The pathogen is internally seed borne. The growth of plant of plant and its general appearance is not affected. Smutted heads consist of deformed spikelets filled with a black, dry, powdery mass of spores which entirely replace all the floral parts and glumes; only ends of the glumes escape transformation. These spores easily separate from the diseased host and are blown off by wind leaving a bare rachis behind.
CAUSAL ORGANISM - The Pathogen is Ustilago segetum var. tritici which was earlier know as Ustilago tritici.
DISEASE CYCLE - Spores fall on the feathery styles of the stigma, they germinate and produce promycelium from which infection threads enter the style and grow forwardly intracellularly until the ovary is reached.
The fungus resides in the kernel as a dormant mycelium and from superficial examination of harvest time, infected grain cannot be distinguish from the healthy one.
At the time of ear formation the fungus enters the reproductive phase.
Although the pathogen is internally seed borne its active phase is visible only in the floral parts. Environmental conditions are important in determining expression of disease.
CONTROL -
1. Immersion of seeds in water soak to which ceresan or sodium hypochloride has been added.
2. Hot water soak (54˚C) for ten minute.
3. Seed dressing with systemic fungicides such as Vitavax and Benomyl at 0.2 - 0.25%. Baristin SD has been found effective.
4. Cultural Practice - Cultural practice are such type of practice which are generally for eliminating the diseased part and to buried it in the ground.