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Post Harvest Diseases:: Vegetables:: Cucurbits

Anthracnose: Colletotrichum lagenarium
Symptom:
  • Older leaves show small, water-soaked or yellowish areas that enlarge rapidly and turn tan to reddish brown 
  • Spots - often circular to angular
  • Later, spots may merge, blighting large sections of the leaf
  • Petioles and stems - Tan to black, elongated and form slightly sunken streaks called cankers 
  • Attacks Watermelon, Cantaloupe, Cucumber
  • Squash and pumpkin are almost immune
  • Immature fruit - turn black, shrivel, and die
  • Round, water-soaked spots develop on the older fruit
  • Spots turn dark green to brown with age and may become sunken
  • Under wet conditions, pinkish-colored spore masses can be seen oozing out of the sunken spots
Water soaked spots on watermelon Concentric rings White mycelium on watermelon Water soaked spots on biottlegourd
Identification of pathogen:
  • Mycelium - septate, hyaline when young and dark when old
  • Setae - brown, thick walled, 2-3 septate
  • Conidia - hyaline, oblong and single celled

Mode of spread and survival:

  • Soil and seed borne
  • Fungus overwinters in old cucurbit vines or in weeds for 5 yrs
  • Anthracnose can appear anytime during the  season, but most damage occurs late in the season after the fruit is set
  • Spread - running water, workers and the insect Pimelia sp.

Epidemiology:

  • Warm, wet conditions - favour rapid development and spread of the disease
  • Temp - 25°C, 100%RH
Management:
  • Field sanitation - destroy the plant debris
  • Hot water treatment of seeds @ 57.2°C for 20 min
  • Seed treatment - thiram or carbendazim or mancozeb @ 2g/kg
  • Spraying at weekly intervals of Carbendazim 0.1 %, Mancozeb 0.2%, Difolaton 0.2%
  • Fruit dip - 5 min in wash water containing 120 ppm of chlorine helps to prevent infection of healthy fruits
  • Resistant varieties in watermelon - Black Stone, Congo, Diamond, Charleston
Source of Images:
http://imgkid.com/anthracnose-of-cucurbits.html

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