What Is It?

What Is It? | Facts in Depth | For the Professional Diagnostician

Brassica Diseases | Black Rot

Black Rot



  • Young seedlings are very susceptible to black rot infection
  • Leaves are chlorotic
  • Premature leaf drop occurs
  • Seedlings eventually die

 Mature Plants

  • Leaf edges are chlorotic or necrotic
  • Lesions form in a distinct “v-shape,” with the base of the “V” directed along the vein
  • Veins are brown to black in color
  • Lesions eventually expand downward toward the base of the leaf
  • Infection spreads down the petioles and up and down the stems
  • Vascular tissues are discolored and exhibit a yellowish bacterial slime
  • Diseased plants wilt and eventually die

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Favorable Environmental Conditions

  • Warm, humid environmental conditions with occasional periods of rain
  • Rain or damp days promote the spread of the disease
  • Temperatures from 75°F to 95°F are most favorable for disease development

Often Confused With

  • Nutrient deficiencies
  • Fusarium yellows

Scouting Notes

  • Scout following periods of rainfall after humid and warm conditions
  • Young seedlings are the most susceptible to black rot infection
  • Very distinct chlorotic V-shaped lesions form on the leaves of mature plants
  • Leaf veins become brown or black in color