Southeastern Apple Production

PLANT PATHOLOGY

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

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.

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.

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Department of Plant Pathology
North Carolina State University
Raleigh, NC 27695 USA

Web Crafters: Anne S. Napier and Steve Schoof
Email: steve_schoof@ncsu.edu

Format updated March 29, 2011