Common Diseases Found in Western North Carolina's Trees
Have you ever wondered if your trees in Asheville, and WNC, are plighted with disease?
We pride ourselves in working to sustain the health and wealth of our beautiful trees, so here is a guide to identify some of the common diseases that could be affecting your trees.
Armillaria Root Rot
Armillaria root rot refers to diseases caused by fungi from the genus Armillaria, mainly A. mellea and A. ostoyae. These fungi are root pathogens for hardwoods and conifers, playing a key role in decomposing dead trees.
Symptoms often mimic other tree issues like drought or cankers, including growth reduction, chlorotic leaves, premature leaf drop, branch dieback, and tree death. Conifers may produce undersized cones during decline. Armillaria creates cankers on the inner bark and lower stem, which can kill roots and cause dieback. After a tree dies, the fungus decays the sapwood.
Distinct signs of Armillaria include white mycelial fans under bark and black or brown rhizomorphs that resemble fine roots. These rhizomorphs can spread through soil, growing up to 8 feet per year, and attaching to tree roots.
Prevention and management can be challenging, as there are currently no effective treatment options available. Ensuring optimal tree health is essential. Choose the right tree species for the specific location, and supply sufficient water and fertilization when needed. If feasible, eradicate any diseased trees and their infected root systems.
White Pine Blister Rust
White pine blister rust is a harmful disease that threatens eastern white pine and related pines with needles in fives. Caused by the non-native fungus Cronartium ribicola, it entered North America in the early 1900s and is now widespread in Western North Carolina with pines. This pathogen affects trees of all ages but is particularly damaging to seedlings and saplings.
Infection of needles by Cronartium ribicola causes yellow to brown spots and bands. The fungus infiltrates pine needles and bark, leading to cankers on twigs, branches, and trunks. A canker is a localized disease area that may appear swollen or sunken, surrounded by healthy tissue. Typically, a white pine blister rust canker has resinous margins and a “blistered” look before breaking open to show Cronartium ribicola’s fruiting bodies, which produce yellow to bright orange spores. As the canker enlarges, it kills all surrounding tissue. Dead branches may retain orange to red needles, creating a striking “flag” that indicates the disease.
There is no definitive cure for trees affected by white pine blister rust cankers on the main stem. When the canker fully encircles the trunk, the tree above it will perish. If branch cankers are within four inches of the trunk, the trunk is likely colonized, increasing the risk of a main stem canker. Pruning branches farther from the trunk can prevent the fungus from spreading. To remove these cankers, prune at least six inches beyond visible symptoms on the trunk side. Eliminating branch cankers and trees with main stem cankers prevents spore production. The fungus dies quickly in discarded branches, posing no further risk to its hosts. To prevent needle wetness, avoid sprinklers on ornamental trees, dense planting, weeds around young trees, or placing white pines in persistently moist, poorly ventilated areas.
