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Stem blight - Phytophthora drechsleri fsp. cajani
Initially purple to dark brown necrotic lesions girdle the basal portion of the stem and later may occur an aerial parts. Initially lesions are small and smooth, later enlarging and slightly depressed. Infected tissues become soft and whole plant dies. In grown up plants, infection is mostly confined to basal portions of the stem. The infected bark becomes brown and the tissue softens causing the plant to collapse. In leaf, localized yellowing starts from the tip and margin and gradually extends towards the mid-rib. The centre of the spots later turn brown and hard. The spots increase in size and cover a major portion of the lamina, leading to drying.


Phytophthora drechsleri fsp. cajani


Fungus produces hyaline, coenocytic mycelium. The sporangiophores are hyaline bearing ovate or pyriform, non-papillate sporangia. Each sporangium produces 8-20 zoospores. Oospores are globose, light brown, smooth and thick walled.
Favourable Conditions

  • Soils with poor drainage,
  • Low lying areas,
  • Heavy rain during the months of July- September
  • High temperature (28-30˚C).

Disease Cycle
The fungus survives in the soil and plant debris in the form of oospores. Primary infection is from oospores and secondary spread of the disease by zoospores from sporangia. Rain splash and irrigation water help for the movement of zoospores.

  • Treat the seeds with Metalaxyl at 6 g/kg.
  • Spray Metalaxyl at 500 g/ha.
  • Adjust the sowing time so that crop growth should not coincide with heavy rainfall.