The usual suspect is the fungal disease Rhizosphaera needle cast, says Yvonne Carree, University of Idaho extension forestry associate. Spread by rain and wind, the fungus overwinters on infected needles. Finally, adjust your sprinkler to avoid hitting foliage and moving spores to new areas, and thin your plantings and branches to encourage good air circulation and speed drying.
Drier environments are less hospitable to successful fungal infections.
If the problem continues, contact your county extension educator or Master Gardener to confirm the diagnosis. Your local lawn and garden outlets stock good, broad-spectrum fungicides, among them Daconil Weather Stick. Carree says organic fungicides work well, too. I read about a study where people were taking 2,000 IU of vitamin E daily. The Recommended Dietary Allowance for vitamin E is 30 IU and the long-term effects of megadoses in healthy people are still very unclear, says Martha Raidl, University of Idaho extension nutrition specialist.