Dothistroma Needle Blight

Dothistroma blight is a devastating foliar disease of a wide range of pine species. The causal fungus, Dothistroma pini Hulbary, infects and kills needles. Premature defoliation caused by this fungus has resulted in complete failure of most ponderosa pine plantings in States east of the Great Plains. In the central and southern Great Plains, D. pini damages Austrian and ponderosa pines in Christmas tree, shelterbelt, and landscape plantings. In California, Oregon, and Washington, the fungus damages plantings of lodgepole and Monterey pines. Infection by D. pini occurs sporadically in natural stands of lodgepole and ponderosa pines in Idaho, Montana, and Washington.

The fungus has seldom been detected in young seedlings in nurseries in the United States. Yet, experience with epidemics in isolated new plantings in the central Great Plains indicates that trees infected in the nursery must have been responsible. The fungus is common on older transplants in nurseries that produce pines for landscape plantings. These nurseries are located in States.

Dothistroma pini occurs in States shown in figure 1 and in southwestern Alaska. Twenty pine species and hybrids are known hosts in the United States. In the Central and Eastern United States, the fungus is found most often in plantings of Austrian and ponderosa pines. These two species are highly susceptible. The fungus has not been reported in natural pine stands in the Eastern and Central United States.