Evergreens offer year-round green landscape color. Long coveted for their ongoing seasonal interest, evergreens fit into many landscapes. Relatively hardy, the trees suffer from very few pests. Often, the foliage of the evergreen changes color. It might taken on a purplish or yellowish hue before the needles begin to dry, turn brown and drop from the tree. Partial or complete death of the tree may occur quickly if the tree is suffering from brown leaf disease.
Diseases that cause needle browning and dropping can occur year-round on a conifer. The tree might exhibit symptoms of needle drop that begins in the top branches of the tree and proceeds downward, or the needle drop might commence around the base of the tree and work its way upward. Brown needle drop often begins in the spring and effects only the tree's new growth. As the disease advances, the new-growth needles drop to the ground and the twigs of the tree begin to die on the north side of the tree, according to the University of Illinois. By autumn, the tree might suffer partial or complete defoliation.
Root rot in the conifers root system can also cause the tree to show signs of browning foliage with severe needle drop. The tree will often begin to exhibit loss of vigor. New growth is limited and quickly dies on the tree. Root rot is caused from a fungus. It begins to proliferate as the root system of the tree remains moist for an extended time period. Evergreen trees should always be planted in a location that offers well-draining soil. A wet root system renders the tree susceptible to root rot, browning of the needles and eventual death.
Diagnosis of browning needle diseases in an evergreen are often difficult to make. Evergreens naturally loose needles as new needles emerge. The tree can also suffer wintertime needle damage from the ground freezing and the tree being unable to receive enough water. When an evergreen goes through a period of drought it will often drop its needles. Natural wintertime damage does not prove fatal to the tree. It will eventually recover, but ongoing diseases can cause the tree's eventual demise. Natural needle loss and winter damage cause the tree to uniformly loose needles, but diseases afflict the tree appearance sporadically.
Apply a fungicide in the spring will help prevent fungal needle diseases of the evergreen from gaining a foothold on the tree, according to the University of Iowa. Fungicides for conifers are widely available and easy to apply. They will quickly help the tree overcome the disease and return it to its normal vigor over the summer months.
Avoid planting evergreen trees that exhibit any browning of the needles because the tree might be unhealthy and suffering from disease, according to the University of Minnesota. Evergreen trees do not wilt, so the only indication of their true health is their green needles. By the time a needles begin to turn brown the tree might be seriously sick and require prompt treatment. Planting only healthy trees will also help keep neighboring evergreens from becoming infected with browning needle diseases.