A Technical Report from The Bartlett Tree Research Laboratories
Dothistroma needle blight (DNB), also known as red band needle blight, is a serious disease of pines. It is caused by the fungus Mycosphaerella pini. DNB has been reported from over 60 countries infecting over 80 different species of pine and several other non-pine species. Austrian, Monterey, and Ponderosa pine are the pine species most susceptible to this disease. DNB infects needles of all ages, causing a reduction in photosynthetic capacity and premature mortality. Symptoms of the disease first appear as light green lesions on needles. Lesions eventually turn tan to reddish brown as the disease develops. It is within these red bands that the small, black, spore-containing fruiting bodies tend to be found with symptoms most apparent in June and July. A distinct transition line forms between the necrotic lesion and healthy green tissue. Needle tips may die back while the bases remain green in severe cases. Premature needle drop occurs, leading to gradual thinning of the canopy. Symptoms are most severe in portions of the canopy located within 6 to 10 feet of the ground.