- The collar rot is manifested as reddish brown water soaked lesions at the base of the stem in contact with soil.
- Under favorable condition, the lesions extend and cause girdling of the stem.
- The stem at the collar region becomes sunken and rotten.
- Thick mycelium and brown sclerotia are noticed in the affected portion at later stages.
- The foliage above the infected stem shows yellowing.
- Defoliation sets in, after lesion formation.
- If the conditions are unfavorable, the lesion does not expand further, but the plant remains weak and stunted.
- Web blight is noticed on the foliage. Initially the symptoms are seen as small necrotic lesions, 5-10 mm wide, with brown centers and pale green margins.
- The leaves show water soaking and rotting.
- On the rotten areas white cobwebby mycelial growth is noticed.
- The adjacent leaves are seen webbed together by the mycelium.
- Sclerotia are also noticed in the affected areas.
The pathogen survives in infected crop debris in soil. Sclerotia can remain in soil for several years. A large number of weed species are known to be sources of survival and primary inoculum of the pathogen. High soil moisture and relative humidity are important for disease development, colonization and survival. Survival is affected by soil temperature. Total inorganic N and ammoniacal N are positively correlated with infection.
Assess the number of plants affected by observing 25 pits at random.