SESAMUM :: MAJOR DISEASE :: STEM BLIGHT

Stem blight - Phytophthora parasitica var. sesami
Symptoms
Black coloured lesions appear on the stem near the soil level. The disease spreads further and affects branches and may girdle the stem, resulting in the death of the plant. Leaves may also show water-soaked patches and spread till the leaves wither. Infection may be seen on flowers and capsules. Infected capsules are poorly developed with shriveled seeds.

Phytophthora parasitica var. sesami -Symptomsq

Pathogen
The fungus produces non-septate, hyaline mycelium. The sporangiophores are hyaline and branched sympodially and bear sporangia. The sporangia are hyaline and spherical with a prominent apical papilla. The oospores are smooth, spherical and thick walled.
Favourable Conditions

• Prolonged rainfall,
• Low temperature (25˚C)
• High relative humidity (above 90 per cent)

Disease Cycle
The fungus can survive in the soil through dormant mycelium and oospores. The seeds also carry the fungus as dormant mycelium, which causes the primary infection. Secondary spread of the disease is through wind-borne sporangia.
Management

• Treat the seeds with captan or thiram at 2g/kg or metalaxyl @ 4g/kg.
• Avoid continuous cropping of sesamum in the same field.
• Remove and destrosy infected plant debris.
• Spray metalaxyl 1kg/ha.