| Oak -- Sudden Oak Death |
| See Also: Tanoak -- Sudden Oak Death ; and Rhododendron -- Ramorum Leaf Blight and Shoot Dieback |
| Cause:
The disease was first reported in 1995 in Mill Valley, CA. Since, many oaks have died throughout the central coastal counties of California. Dying trees have been observed in urban and rural forests and woodlands. A fungus-like organism, Phytophthora ramorum, killing tanoaks, wild rhododendrons, and evergreen huckleberry in a few isolated spots just north of Brookings, OR, was found during the summer of 2001. There was also incidental leaf infection on salmonberry, cascara, myrtlewood, and poison oak (stem cankers). No oaks were involved. Eradication of infected plants began soon after the sites were found. The infestation remains limited in Oregon, confined to isolated spots of forest land near Brookings. Federal and international quarantines have been established to prevent the spread of this pathogen in soil and infected plant material.
The host list for this organism includes many different plants. Tip dieback and/or leaf spotting occurs on bigleaf maple, cascara, coast redwood, Douglas fir, honeysuckle, horsechestnut, huckleberry, kinnikinnick, myrtlewood, Pacific madrone, poison-oak (stem cankers), rhododendron cultivars, salmonberry, Viburnum and others. Lethal bark cankers develop on susceptible members of the oak family, such as black oak (Quercus kelloggii), coast live oak (Q. agrifolia), Holm oak (Q.ilex), southern red oak (Q. falcata), Shreve’s oak (Q. parvula var. shrevei) and tanoak (Lithocarpus densiflorus). |
| Notes: This disease and fungus are different from the outbreak of P. cinnamomi in southwest Mexico that has similar symptoms on oak. |
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References: Rizzo, D.M., M. Garbelotto, J.M. Davidson, G.W. Slaughter, and S.T. Koike. 2002. Phytophthora ramorum as the cause of extensive mortality of Quercus spp. and Lithocarpus densiflorus in California. Plant Disease 86:205-214. The California Oak Mortality Task Force http://www.suddenoakdeath.org |
| Content edited by: Jay W. Pscheidt on January 1, 2009 |
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