SESAMUM :: MAJOR DISEASE :: ROOT ROT OR STEM ROT OR CHARCOAL ROT

Root rot or stem rot or charcoal rot - Macrophomina phaseolina(Sclerotial stage: Rhizoctonia bataticola)
Symptoms
The disease symptom starts as yellowing of lower leaves, followed by drooping and defoliation. The stem portion near the ground level shows dark brown lesions and bark at the collar region shows shredding. The sudden death of plants is seen in patches. In the grown-up plants, the stem portion near the soil level shows large number of black pycnidia.

Macrophomina phaseolina - (Sclerotial stage - Rhizoctonia bataticola) - Symptoms

The stem portion can be easily pulled out leaving the rotten root portion in the soil. The infection when spreads to pods, they open prematurely and immature seeds shriveled and become black in colour. Minute pycnidia are also seen on the infected capsules and seeds. The rotten root as well as stem tissues contains a large number of minute black sclerotia. The sclerotia may also be present on the infected pods and seeds.
Pathogen
The pathogen produces dark brown, septate mycelium showing constrictions at the hyphal junctions. The sclerotia are minute, dark black and 110-130µm in diameter. The pycnidia are dark brown with a prominent ostiole. The conidia are hyaline, elliptical and single celled.
Favourable Conditions

• Day temperature of 30˚C and above
• Prolonged drought followed by copious irrigation.

Disease cycle
The fungus remains dormant as sclerotia in soil as well as in infected plant debris
in soil. The infected plant debris also carries pycnidia. The fungus primarily spreads through infected seeds which carry sclerotia and pycnidia. The fungus also spreads through soil-borne sclerotia. The secondary spread is through the conidia transmitted by wind and rain water.
Management

• Seed treatment with carbendazim + thiram (1:1) at 2g/kg seed.
• Treat the seeds with Trichoderma virideat 4g/kg.
• Apply farm yard manure or green leaf manure at 10t/ha or neem cake 150 kg/ha. Spot drench with Carbendazim at 1.0 g/litre.