Evergreen Needlecast Diseases are caused by several fungi. Needles infected with fungi generally fall several months after the actual period of infection. The period of greatest infection for most needlecast fungi is during the late Spring and early Summer months. Symptoms, the visible indication that the needle is diseased, do not appear until the late Winter, Spring, and early Summer of the next year.
All the needlecast fungi form small structures on the infected needle in which thousands of spores form. These "fruiting structures" may be black, orange-red, or tan, depending on the fungus. Other fungi that grow on dead or dying needles but do not cause needlecast may form similar structures. Finding a fungal fruiting structure on a dead needle is not proof that the tree has a needlecast disease.
Managing Evergreen Needlecast Diseases
Needlecast fungi require abundant moisture for their growth and development. Therefore, plant so that the air circulation around trees will be good. Maintain good weed control so that tall weeds do not impede air circulation around the lower branches. Avoid planting susceptible trees in law or shady areas where humidity and needle wetness tends to be high for prolonged periods. The fungicides listed below can be applied to protect healthy foliage. If needles are already infected, a fungicide will not prevent their falling off the branch.