Diseases of African sumac ( Rhus lancea ) in Arizona
Ganoderma root rot
Ganoderma root rot in African sumac (Rhus lancea) is caused by the soil borne fungus Ganoderma lucidum, a member of the group of basidiomycetes known as polypores. The fungus is soil borne and infects roots, particularly at wound sites. It rots the roots causing a slow decline and death of mature trees (photo 1). It can move from tree to tree via root contact, but is not found in upper parts of the tree.
The only distinguishing sign of disease is the appearance of fruiting bodies at the base of the tree (photos 2 and 3). These growths are most common during the summer rainy season, and start out as white bulbous structures at soil level (photo 4). If they continue to grow, the fruiting bodies become shelf-like structures that are reddish brown and glossy on the top and cream colored on the bottom (photos 5 and 6). Spores released from the bottom may leave a reddish brown dust on the soil and trunk nearby.
There is no recommended treatment for infected trees. The best way to prevent infection is to prevent wounding. Cutting roots during construction or landscape maintenance should be avoided wherever possible. Native trees that have been disturbed during construction activities are particularly vulnerable. Since the fungus survives in the roots of dead trees, it is important not to replant a susceptible plant in the same site. The host range of Ganoderma in landscape ornamentals in Arizona continues to grow and includes, but is not limited to, ash, citrus, mesquite, olive, pyracantha, Heritage oak, California pepper, willow, mulberry, elm, carob and locust.
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August 7, 2013