Following periods of rain mushroom hunters venture out into the hills of Sonoma County in search of edible mushrooms. But in your home landscape mushrooms may be an indication of a potential deadly root fungus that can weaken or kill our native oaks. While many mushrooms are harmless, the presence of some mushroom species growing on or near oak trees is a reason for concern.
Armillaria mellea
December is a good time to check the trunks of your oak trees for signs of potential root fungi. One of the more common mushrooms that are associated with native oaks is known as honey fungus. Honey colored clusters of these mushrooms are an indication of Armillaria mellea, a pathogen that causes the tree’s roots and stem to rot. This in turn, causes a reduction in tree vigor and can potentially result in the tree falling over. Check the lower trunks and the soil near the tree trunks and roots for these honey-colored mushrooms. Mushrooms are not always present when Armillaria has infested the tree. Excavating the soil at the tree base to identify decayed wood near the ground and roots should performed, especially for trees of low vigor or that have defects in the bark.
Armillaria is present in many oak roots, but during periods of stress the severity of the pathogen increases. Our recent drought is an important factor contributing to stress in our native oak trees.
It is also important to check lower trunks for cracks or loose bark. This may indicate dieback of the cambium area of the tree from fungal activity.
Reducing risks of Armillaria mellea
There are best practices to reduce the likelihood of damage to your oak trees from Armillaria. Be sure that mulch or soil is not piled around tree trunks which can lead to greater chances of root fungi entering through the bark. Irrigation near oaks in summer months also contributes to the development of harmful fungal infections. Warm moist conditions are ideal for the growth of fungi.
Oak species susceptible to Armillaria
Armillaria is the most common fungus that affects Valley Oak trees in Sonoma County. Valley Oaks are known as a Riparian tree which means they are commonly found near waterways. These are the majestic trees in the Laguna de Santa Rosa area that can be seen as you travel between Sebastopol and Santa Rosa along Highway 12. Valley Oaks are also prevalent in the Sonoma Valley area along Highway 12 from Santa Rosa to Kenwood and Oakmont. They are also native to the Santa Rosa, Windsor and north to Healdsburg and Cloverdale.
Reducing risks from fungi and tree decay
If you have Native Oaks in your home landscape the best way to ensure their health is to have your trees inspected by a Certified Arborist periodically. Give TreePro a call today for a no cost inspection of the oak trees at your home. A Certified Arborist will inspect your trees for health and structure to promote tree longevity and reduce hazards.