Brown Leaf Disease on Evergreens

When it comes to controlling brown leaf disease on evergreens, you first need to identify the problem. Many different diseases and other conditions can cause needles to brown, so identifying the one affecting your tree will allow you to take the proper method in combating it. Disease can enter through wounds in the tree or by insects. Weak or stressed evergreens are most susceptible to contracting diseases.

Caused by the fungus Rhizosphaera kalkhoffii, this disease results in loss of evergreen foliage on spruce trees. According to the University of Illinois, infections start in spring, affecting lower branches first and working up. Afflicted foliage turns mottled yellow in late summer and by winter they turn brown. The dead foliage then falls the next summer. Fruiting bodies sometime appear in rows on infected needles.

Pine wilt occurs with an infestation of Bursaphelebchus xylophilus, or the pine wood nematode. Other insects like the Sawyer beetle carry nematodes from tree to tree. Once these nematodes affect a tree, they breed quickly and eventually kill the tree. Once infected, an evergreen becomes stunted and the foliage fades. Older needles turn yellow and fall off while young needles turn brown. Other types of nematodes can also infect trees, but not as seriously as the pine wood nematode.

When an evergreen gets an infection of scleroderris canker, the needles on branch tips turn brownish orange at the base while staying green at the tips. As the disease progresses, all the needles turn brown. Newer growth turns first, with older growth becoming infected later. In addition, the needles fold back along the stem and wood beneath the bark gives off a greenish cast. This disease affects young plantings more seriously than older trees.

Also termed diplodia, sphaeropsis blight comes from the fungus Sphaeropsis sapinea and affects conifers, particularly pines. This fungus attacks older trees although young trees near infected old trees can get the disease as well. Among the symptoms, new shoots and needles twist and stunt, turning brown. New growth often droops because of infected stems. In addition, resin forms at the base of infected needles, causing them to stick to the tree.

While you can control brown leaf diseases on evergreens by spraying with a fungicide, you can also take other steps to reduce the spread and severity of these diseases. For example, you can remove affected parts and clear debris from the base of the tree. Some diseases require complete removal of the infected tree. However, before treating any evergreen, you must properly identify the disease in order to apply appropriate fungicides.