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Post Harvest Diseases :: Cucurbits

Alternaria rot- Alternaria alternata

  • In fruit minute black lesion appear
  • Dark grey, sunken irregular lesions developing lengthwise.
  • Grey cottony mycelial mat bearing conidia appeared on the surface of developing lesions
  • Necrotic tissue of the infected fruit
  • Low temperature enhance the diseases

Fruit rot     Pythium aphanidermatum.

  • Cause Damping-off or vine cankers during unusually wet seasons, but fruit rot  prevalent symptom.
  • The fungus penetrates fruit wounds and old flower parts, as well as plant parts touching the soil.
  • Fruit rot begins as a dark green water-soaked area.
  • Wet mushy rot develops rapidly and may become covered with white cotton mold during wet weather.
  • The fungus will spread by fruit-to-fruit contact

Gummy stem blight (GSB)

  • Important disease of greenhouse cucumber.
  • Didymella bryoniae, previously known as Mycosphaerella melonis.
  • In favorable weather, the pathogen can infect all parts of the cucumber plant during all phases of plant growth
  • Tan-colored lesions with black pinpoint spore-producing structures on cucumber stem.
  • V-shaped lesions on cucumber leaf, where spores entered through guttation droplets; on left with early symptoms of pre-harvest internal fruit rot, on right with severe symptoms of post-harvest rot.
  • After spore germination, conditions of high relative humidity, low light and temperatures between 20-28°C promote the growth and spread of the fungus
  • Disease symptoms appear within 4 to 8 days of initial infection.
  • Fungus produces spores invisibly spreading through the greenhouse.

Black rot

  • Most important disease contracted during storage of squash (butternut, Hubbard, and others), pumpkin, and even gourds in the Northeast.
  • Affected fruit may show black rot lesions in the field before harvest, collapse soon after harvest, or exhibit lesions some time later in storage Black rot, the phase of the disease called gummy stem blight that infects fruit, is caused by the fungus Didymella bryoniae as the sexual stage and Phoma cucurbitacearum as the asexual stage
  • Ring pattern showing black specks (pycnidia) of the black rot on pumpkin.
  • Black rot symptom developed on butternut fruit in storage, beginning as a bronzed-colored, water-soaked lesion, followed by mycelial development of Didymella bryoniae.
  • Large Halloween pumpkin showing the initial stages of black rot following injury
  • Advanced development of black rot on surface of pumpkin

Anthracnose (Colletotrichum orbiculare)

  • Sunken and nearly circular spots present on the infected  surface of pumpkin .
  • Lesions may be fairly large, and are circular to irregular in shape

Sclerotinia white mold - Sclerotinia sclerotiorum

  • It develops in the field on melons and pumpkins or in storage on winter squash.
  • White cottony mold and the presence of black, pea-sized resting bodies (sclerotia) are important signs of the fungus.

Phytophthora Fruit Rot (Phytophthora capsici

  • Fruit rot of processing pumpkin caused by P. capsici:
  • Lesions appear on fruit surface;
  • Fruit rot developed on the side contacting the soil;
  • Fruit rot as a result of falling an infected leaf on fruit
  • Severely infected fruits are collapsed.
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