How to Manage Pests

Pests in Gardens and Landscapes

Annosus root disease—Heterobasidion annosum or Fomes annosus

Annosus root disease is a fungal disease that can infect the roots or butt of many conifers and some hardwoods. Disease presence may be indicated by conks. These vary in form, often forming a small button, seashell-like bracket, or amorphous whitish, gray, or light brown growth, usually around the root crown. Bark may separate readily from wood in infected trees; the separated surfaces are light brown and the wood surface is often streaked with darker brown. Numerous silver or whitish flecks may also appear on the inner bark surface, and small whitish mycelial growths may occur between outer bark scales or on the bark surface.

Life cycle


Avoid wounding trees. Apply borax to freshly cut pine stumps in areas where pines grow naturally to prevent infection by Heterobasidion annosum, which can spread from stumps through roots to nearby pines.

annosus infection in tree trunk
Annosus infection in tree trunk

Statewide IPM Program, Agriculture and Natural Resources, University of California
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