Root Rot in Fir Trees


Root rot is a very dangerous plant disease. Once it infects fir trees, they are doomed. Gardeners can take precautions against root rot by following proper planting and care practices. Learn to recognize the symptoms of root rot in fir trees to stave off the fungal disease and protect other trees in the yard.

Armillaria Root Rot

Initial symptoms of Armillaria root rot occur underground when the fir tree's roots begin to rot from contact with standing water. Above ground, small tan or cream-colored mushrooms form near the fir tree's trunk. The mushrooms range from 4 to 6 inches high with 2- to 4-inch wide caps and may show brown freckles. Trees also ooze brown sap or liquid from the trunk or infected branches. Gardeners can dig under the soil to expose additional fungal bodies in the roots.

Phytophthora Root Rot

As with Armillaria root rot, Phytophthora root rot's initial symptom happen underground when a tree's roots begin to rot. This root rot's symptoms are not as noticeable as Armillaria root rot. The needles on infected fir trees begin to turn yellow or brown. Branches may die, will feel hollow to the touch and won't move in the wind. This disease is more prevalent in warm weather.


There is no treatment for infected trees. They will eventually die. By the time a gardener notices the symptoms, the root rot infection is generally quite severe. Gardeners should cut down and dispose of infected trees, because bacteria can spread to other trees. The site remains contaminated with fungi for several years; gardeners should remove the soil before planting susceptible plants in the location.


The best way to prevent root rot in fir trees is by planting the trees properly and providing the right care. Fir trees contract root rot when they are planted in poorly draining soil. To test whether your soil is draining well, dig a hole 12 inches wide by 12 inches deep. Fill the hole with water, then allow the water to drain into the soil. When the hole empties, fill it again with water. Time how long this batch of water takes to seep into the soil. Well draining soil will lose 1 inch per hour, so if your soil is significantly slower, do not plant fir trees in that area. After planting, provide trees with adequate water, but do not water during rainy periods.


Armillaria root rot infects about 500 types of woody plants, including many species of fir. Oregon State University Extension notes that Douglas fir, grand fir and white fir can all become damaged. Phytophthora root rot infects in all types of firs, including Fraser.

Keywords: armillaria root rot, phytophthora root rot, fir tree rot, fir root rot

About this Author

Based in Northern California, Elton Dunn is a freelance writer and nonprofit consultant with 14 years' experience. Dunn specializes in travel, food, business, gardening, education and the legal fields. His work has appeared in various print and online publications. Dunn holds a Master of Fine Arts in creative writing and a Bachelor of Arts in English.