A fungal disease that kills needles of pine trees
Dothistroma is a fungus that infects the needles of Austrian, Ponderosa, Red, Mugho, and Scotch pines. Reddish-brown spots and bands form in the infected needles, giving the disease its alternate name of red-banded needle blight.
Diseased trees can be managed
Dothistroma needle blight can be controlled, but not cured, with sprays of fungicide. As with any needle blight disease, the aim of spraying the tree is to break the annual cycle of infection in the new needles. Multiple seasons of treatment are needed before results are noticeable in the tree. Needle blight diseases tend to return within a few seasons if spray treatments are discontinued.
What to look for
• Reddish-brown spots and bands form in the needles
• Infected needles drop from the tree
• Symptoms are most prominent in the lower six feet of the tree
• Fungus overwinters in infected needles.
• Infection of new needles takes place spring through autumn through spores moved by splashing of rain drops.
• The time period between infection and appearance of symptoms varies from 5 weeks to 6 months.
Treatment and Prevention
• Promote air flow by reducing density of plants around pine trees
• Modify irrigation system to avoid wetting needles; prolonged needle wetness favors fungal infection.
• Mulch the tree or treat it with Forest Floor Service
• Provide low level nitrogen fertilization
• Your consulting arborist may recommend fungicide sprays to control Dothistroma. Sprays will not cure the disease, but can increase the tree’s longevity in the landscape.