Pythium root rot of Onion
Pythium root rot of onion is caused by three species of fungus viz. Pythium aphanidermatum, P. debaryanum and P. ultimum
Pythium root rot is characterised by seed rotting and pre-emergence damping off.
The disease appears in circular patches in the field here and there.
All the affected plants can get killed. if the disease occurs prior to seed germination
The disease may occur after establishment of the crop after 15 to 30 days of sowing or planting and such stage is called as post-emergence damping off.
In cases where the disease occurs late, then stunting of the plants and rotting of the roots is observed
ThePythium fungus is mainly soil borne.
The disease is favoured by ill drained conditions in the field due to stagnation of water.
High soil moisture or continuous rain may favour rapid development of the disease.
To control the disease, Seed treatment with Thiram or Captan @ 4g/kg is highly recommended by agriculture expert
After sprouting, the root region of the plants along the rows should be given a soil drenching with Copper oxychloride 0.25%.
The bulbs can be dipped in Thiram solution 0.25%.