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Title: Sudden Oak Death (Phytophthora ramorum) and lilacs

item Shishkoff, Nina

Submitted to: Lilacs- Quarterly Journal of the Iternational Lilac Society
Publication Type: Other
Publication Acceptance Date: 5/22/2007
Publication Date: 10/1/2007
Citation: Shishkoff, N. 2007. Sudden Oak Death (Phytophthora ramorum) and lilacs. Lilacs- Quarterly Journal of the Iternational Lilac Society. Fall 2007 Edition.

Interpretive Summary: Lilacs are one of the hosts of Phytophthora ramorum, the pathogen responsible for the deaths of hundreds of thousands of oak trees on the west coast of the United States. This paper details the symptoms on lilac, the epidemiology of the disease, and the relative susceptibility of a number of lilac cultivars. This allows readers of the journal “Lilacs”, hobbyists and nursery growers, to better understand the disease, what it looks like on lilac, and why the quarantine is important to reduce the risk of P. ramorum to eastern forests.

Technical Abstract: In the 1990s, Californians began to notice that native oaks were dying in unusual numbers. By 2001, it was clear that a new pathogen, Phytophthora ramorum, was causing the stem cankers on oaks and foliar lesions and stem dieback on a number of other plants, in the U.S. and in nurseries in Europe. At first only a handful of host plants were known, but the list currently includes almost 50 genera. Among these hosts is lilac. In 2003, the first infected lilacs were found in British nurseries. In 2004, an infected lilac was found in a nursery in New Jersey and in 2006 one was found in Maine. Since lilacs are a popular ornamental and P. ramorum sporulates abundantly on them, it is important to be able to recognize symptoms of the disease and understand how the disease spreads in a nursery situation. It may also be useful for plant breeders to know if there are sources of resistance in Syringa. This paper outlines the current situation for the disease, including quarantine and regulatory issues, and discusses what is known about P. ramorum on lilacs: symptomology, epidemiology, and relative susceptibility of cultivars.