Diseases of ash (
Ganoderma root rot
The fungus Ganoderma lucidum causes Ganoderma root rot in ash (Fraxinus velutina). It is 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. 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 4 and 5). 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, minimize environmental stress such as drought, and provide proper cultural care. Cutting roots during construction or landscape maintenance should be avoided whenever possible. 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 probably not limited to Africam sumac, citrus, mesquite, olive, pyracantha, and Heritage oak.
Ganoderma lucidum is also known as the Chinese Ling Chi and the Japanese Reishi; it is considered a medicinal mushroom in the Orient and is grown by mushroom hobbyists.
Links for more Information:
http://cals.arizona.edu/pubs/diseases/az1124.pdf
(page 18)
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74109.html
http://www.ppath.cas.psu.edu/EXTENSION/PLANT_DISEASE/ash.html
http://cals.arizona.edu/yavapai/anr/hort/byg/archive/growingmushrooms.html
http://cals.arizona.edu/pima/gardening/aridplants/Fraxinus_velutina.html
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February 17, 2006