Diplodia Shoot Blight and Canker

Scientific Name: Diplodia sapinea

Diplodia is a fungus that will survive in new candles of conifers and will eventually infect the main stem of the tree. While it is in the candles, at the “blight stage” it can be controlled through the continuous use of fungicides over a period of several years. When the disease is in the “canker stage” on the main stem of the tree, the only management that can be done is to increase the vigor of the tree and enhance its ability to callus over the infected tissues. This procedure will not cure the tree, but will increase its longevity in the landscape.

Attacks: Red, Austrian, Scots, Mugo, White, and Ponderosa pine; Spruce; and Douglas fir

• Once the tree is diseased it will never be cured

What you will see:

• Shoot blight phase:
  • Brown shoot tips
  • Black fruiting bodies (pycnidia) at base of needles and on old cones
• Canker Phase
  • Cankers with enormous amounts of sap
  • Bleeding cankers
  • Gray to black staining of the sapwood
  • Black fruiting bodies under bark in the canker

Life cycle:

• Fruiting bodies begin to form in the fall and the following spring on:
  • Needles
  • Sheaths
  • Cone scales
  • Bark
• Fungal spores are dispersed by splashing water
• Infection can occur throughout the growing season
• Blights and cankers can both be on the same tree

Cultural practices:

• Enhance Growth
  • Reduce stress in environment by reducing or enhancing watering
  • Increase tree vigor
    • Tree nutrition (Pro-growth or Booster)
    • Mulch with low C/N POM
    • Root Enhancement System
• Reduce source of inoculum
  • Prune affected branches in fall or early spring
  • Clean pruning tools between cuts with 5% bleach and 70% alcohol
  • Remove fallen limbs
  • Rake up and remove dead foliage

Chemical

• Chemicals can manage the blight stage of the disease
• No chemical control is available for the canker stage
• Consult with your Arborist for recommended treatment

 

An integrated approach

When caring for urban trees it is important to make a complete evaluation of all environmental conditions to accurately diagnose all stress factors and prescribe care based on specific circumstances. This prescriptive care will help your tree meet its full potential.