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White Root Rot

Scytinostroma galactinum (synonym Corticium galactinum)

White root rot, caused by S. galactinum, is scattered throughout the southeastern Appalachian fruit growing region. Although the disease is found in many orchards, it is usually not widespread. Tree losses may increase as higher density orchards replace older, lower density ones because of the greater likelihood of tree-to-tree spread through root contact.

Symptoms

Aboveground symptoms of white root rot are similar to those of other root rots, but symptoms often progress much faster once infection has occurred. Infection can occur on large roots or at the tree collar. Infected roots are covered with a white to cream-colored mycelial mat that is readily visible when the tree is pulled or roots excavated (Fig 1). Affected roots are soft, lightweight, and crumble easily when touched.

Fig 1 - Mycelial mat on roots
Fig 1. Mycelial mat on roots

Disease Cycle

The fungus that causes white root rot has a large number of hosts in the wild, including oak, dogwood, and holly. Consequently the disease is often most severe on newly cleared land, but it can be a problem in replant sites as well. S. galactinum can survive in roots in the soil for many years. Replants into infested sites usually die in 2 to 3 years.

Control

There is no effective control and replanting infested sites is seldom successful. If replanting is attempted, remove all old roots from the site.

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Format updated March 29, 2011