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Stewart's Bacterial Wilt and Blight

In-Depth Downloads

Symptoms

Yellowed/bleached leaves are early symptoms of bacterial wilt

Early Season Systemic Wilt

  • Occur soon after plant emergence
  • Yellowed or bleached leaf streaks (photo above)
  • Internal vascular discoloration, crown decay, rot (photo below)
  • This phase of disease may result in plant death
early season systemic wilt can cause internal vascular discoloration

Later Season Foliar Blight (photos below)

  • After tasseling
  • Fully developed typical elongated lesions
  • Lesions are long, narrow and have a wavy margin
  • Yellowish border may be present
  • Note blackish appearance of lesions (saprophytic fungal spore production)
  • This disease phase rarely results in plant death, but may predispose for stalk rots
 
Stewart's bacterial blight lesions
Late-season Stewart's bacterial blight

 

Disease Development

Disease is Vectored by Corn Flea Beetles:

  • Bacteria overwinter in insect gut
  • Beetles feed on plants in spring
  • Insect "etches" leaves (whitish areas in photo below)

Two Phases of Disease:

  • Early season systemic wilt
  • Later season foliar blight
Flea beetles feeding on young corn plants

 

Disease Cycle

Stewarts Wilt Disease Cycle

 

Impact on Crop

Yield loss from this disease may occur for a number of reasons:

  • Early season systemic wilt reduces stands and weakens plants
  • Foliar symptoms reduce functional leaf area, reducing photosynthesis and sugar production
  • Stalk rot potential is increased
    • When demand for sugars to fill the ear exceeds supply from damaged leaves, the plant takes available sugars from stalks instead, increasing stalk rot potential

Management

Plant Resistant Hybrids

  • Pioneer rates its hybrids for resistance
  • Contact your local Pioneer sales professional

Control Flea Beetles

  • Systemic insecticide seed treatments help to reduce flea beetle populations
  • Foliar insecticides may be needed in some cases
    • Scout for flea beetles and apply insecticides if insect populations exceed thresholds established by your state
  • Predict flea beetle / Stewart's wilt occurrence
    • Sum the mean temperature for the months of December, January and February
    • Risk increases with the sum of mean temperature - See extension materials from your state
flea beetles

 

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