Dothistroma Pine Needle Blight

One of the most common fungal diseases to affect pines is dothistroma. This disease affects over thirty species of pine trees, and is responsible for much of the premature needle drop associated with urban pine. This disease can kill younger hosts; older trees will continuously defoliate and eventually lose their esthetic value

Affected trees: Austrian pine, ponderosa pine, mugo pine, and scotts pine in some rare cases.

Noticeable signs

Common signs of dothistroma tend to show:

  • scattered spots begin in fall but are barely¬† noticeable
  • older needles vary in color from yellow to red, eventually turning brown by mid-summer to fall.
  • spots often develop into red bands that encircle the needles, turning brown and then dying towards the tip while the base remains green.
  • After the needles die, black fruiting structures appear on the outer needle tissue; .
  • Infections will cause premature needle drop, typically in lower branches first. .

Treatment / Management 

Two to three fungicidal spray applications in spring, starting at bud and continuing every 3 to 4 week intervals.  The first spray protects older growth while the second and or third protects new growth. Treatment for dothistroma will not cure the disease, but it will stop the progression of it.