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Post Harvest Diseases:: Vegetables:: Tomato

Southern Blight: Sclerotium rolfsii
Symptom:
  • Hot weather disease.
  • Mature plants are attacked just below the soil surface and are completely girdled.
  • The tops wilt and die rapidly.
  • Mycelium often grows over the diseased tissue and surrounding soil forming a white mat of mycelial threads with the typical tan-to brown, at the crown mustard-seed-sized sclerotia.
  • Often the entire root system is destroyed.
 
  Gridled surface Mycelium growth Infected plant

Identification of pathogen:

Fungus:

  • Fungus is exceedingly destructive on ground crops and attacks the fruit where they contact the soil.
  • Slightly sunken, yellow spots develop on invaded fruit, which rapidly decay, collapse, and become covered by a white fungal mass with numerous sclerotia.
  • Pathogen spread
  • Soil borne, machinery or water-moved infested soil, survives on numerous weed and crop hosts

Favourable condition:

  • Wet periods of high temperatures (85-95 °F)

Spread and survival:

  • Fungus is exceedingly destructive on ground crops and attacks the fruit where they contact the soil.
  • Slightly sunken, yellow spots develop on invaded fruit, which rapidly decay, collapse, and become covered by a white fungal mass with numerous sclerotia.
  • Soil borne, machinery or water-moved infested soil, survives on numerous weed and crop hosts

Management:

  • Crop rotations of two years or more to a non-host crop like corn or small grains will help to prevent build-up of inoculum and disease problems
  • Close plant spacing and over-irrigation promote disease development and should be avoided

Content validator:
Dr. M. Deivamani, Assistant Professor, Horticulture Research Station, Yercaud-636602.

Source of Images:
http://edis.ifas.ufl.edu/pp272
http://erec.ifas.ufl.edu/images/plant_pathology_guidelines/figure_43.jpg

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