Nine types of true fir trees grow in North America, with the majority of these trees found in the northern states or in high elevations. Among them are the balsam fir, the California red fir, the Fraser fir, the subalpine fir and the white fir. Like all tree species, the firs are vulnerable to certain diseases, most of them brought on when certain fungi gain access to the tree. Some are only a cosmetic nuisance while others are more serious.
Annorous Root Disease
A disease called annorous root disease affects fir trees, precipitated by a fungus that brings about the formation of what botanists call conks. These structures can look like seashells and develop on the crown of the roots. They eventually cause the bark of the fir to separate from the inner wood. This disease will usually kill pine trees, but firs are luckier in that normally the affliction simply causes some decay in the inner wood of the tree. However, this can weaken the tree and leave it at the mercy of other diseases. The fungus has the ability to live for decades within the roots of an infected tree, meaning any other fir tree's roots that contact them will also come down with the ailment.
Needle Cast Diseases
Needle cast diseases are common problems for fir trees in North America. Different kinds of fungi--including those from the families such as Lophodermella, Elytroderma, Rhabdocline, Phaeocryptopus and Rhizosphaera--precipitate needle cast. The symptoms include dark-colored lesions on the fir tree's needles, or spots on both the stems and the needles. The wood of the infected branch can experience tissue death known as cankers and the entire branch, or part of it, can succumb to the disease. The fungi that cause needle cast require damp weather to thrive and infect other needles on the tree.
Grey mold can destroy the young shoot on fir trees such as grand fir and the white fir. A fungal malady, grey mold wilts these shoots and dries them up. Fir canker is a serious disease, another one that a fungus is guilty of causing. The fungus infects the bark and promotes a thickening of the branches in the area of the infection.
If it gets into the tree trunk, the fungus kills the tissue, sometimes around the entire circumference of the tree, making it prone to snapping off in high wind and poor weather. The salt put on roads in the snowy and icy areas where many firs exist will get into the soil near the highway. This high level of salt in the ground adversely affects the tree as it absorbs it through the roots. It can then change needles to yellow or red and make them come off the tree prematurely, almost like the effects of a bad dry period would.