Diseases Of Evergreens

Needle Cast of Spruce

• The fungus known as Rhizosphaera kalkhoffii is responsible for needle cast of spruce trees. This is a disease that usually causes the tree to lose its needles prematurely but fails to kill the specimen. Needle cast of spruce does make the tree unsightly. Colorado blue spruce is particularly vulnerable. In most instances, the lower branches show signs of losing needles before the upper ones. Severe infestation kills the lower branches. Needles infected in late spring turn purple or brown before falling off in autumn. Black spots are the fungus present on them. A chlorothalonil fungicide applied in spring as the new needles emerge is a recommended treatment of this disease, notes the Ohio State University Extension.

Cytospora Canker

• Cytospora canker affects many types of evergreen trees and shrubs, including blue spruce and its hybrids, Norway spruce, white spruce, hemlock and Douglas fir. The fungal malady starts low on the tree and makes its way up to the higher branches in time. The dead, brown needles may or may not fall off the limbs. Dead areas develop on the trunk and the branches eventually killing the tree in worst-case scenarios. Trees 15 years old and older are usually the victims of cytospora canker. Keeping the trees watered during drought, avoiding injuring the trunk or branches, and pruning back any affected branches prevent this disease or limit its spread.

Sphaeropsis Blight

• Pine trees with their needles in bundles of twos and threes, including species such as red pine, Austrian pine, Mugo pine and Ponderosa pine, are at risk from Sphaeropsis blight. This evergreen disease results in brown, shortened new growth, with this symptom normally appearing first on the lower branches of the pine. Any stress on the tree makes it possible for entire branches to fall victim to the disease, with trees weakened by poor soil, compacted soil, lack of water or damage to the trunk and/or roots highly vulnerable. Spraying trees with compounds including thiophanate-methyl or propiconazole 3 before new needles bud out helps keep this disease in check, according to the Nebraska Forest service.

Cercospora Blight

• Eastern red cedar trees and juniper species, planted close together such as in a windbreak setting, sometimes contract Cercospora blight. Foliage in the inner portion of the evergreen dies first once infected, with the fungal disease then moving outward and upward on the tree. Small branches sometimes fall off from the interior as the disease takes hold. Rain spreads the spores of the fungus in early summer. Control this disease by removing trees that are too close to one another, which increases air circulation and discourages fungal growth. Spraying the trees thoroughly with a fungicide can stop the infection