What is Armillaria Root Rot?

Armillaria root rot is a severe fungal disease that affects trees, woody plants, and some herbaceous plants including palms and succulents.

Also known as oak root fungus, Armillaria root rot can rapidly kill trees and presents a challenge to management since infected woody roots can persist for years underground. No plants are completely immune to Armillaria root rot, so prevention is key. Deeply planted trees are often more susceptible to this disease.

The distinctive “honey mushrooms” growing from the base of a tree signals an infection, but they may not always be present. Other visible symptoms include flat cankers on the trunk, wilting, and canopy...

Landscape trees provide welcome shade, fruit, homes for wildlife, and even a place for kids to climb. But if the wood is damaged, disease-causing fungi can infect the tree. A number of fungal diseases decay wood in both tree branches and trunks, weakening and sometimes killing the tree. Wood decay can be hazardous when infected branches and trunks fall.

In the December 2013 issue of the Green Bulletin, we looked at “Pruning and Tree Physiology: The Bad and the Ugly” for pruning and maintaining ornamental trees as well as some pruning pitfalls. However, pruning can also be highly beneficial for many landscape trees. In this article I will review some approaches to pruning which either directly suppress pests or which maintain tree health, and because impaired health predisposes trees to a number of diseases, these pruning measures could thus be considered a part of an integrated pest management program.

Formative pruning: A young tree arriving from the nursery or...