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Since 2015, Extension specialists from Virginia Tech (VT) have visited and collected plant and soil samples from several large areas of dying great rhododendron (Rhododendron maximum) in Virginia’s mountainous regions. In 2016 VT specialists met with Virginia Department of Forestry, US Forest Service personnel, and other experts to revisit some of these sites. No consistent cause of this mortality has yet been identified. It is possible that a variety of factors are stressing the rhododendrons in these areas to a point where opportunistic pathogens or insects can successfully attack and kill them. The following information summarizes our observations and diagnostic results from four separate great rhododendron mortality sites in Virginia. This information is not equivalent to a research study, which would also include samples taken from healthy great rhododendron for comparison; however, we are confident that we have ruled out two diseases that are frequently mentioned both online and anecdotally as a cause of this mortality, specifically Phytophthora root rot and Botryosphaeria dieback.
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Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
August 21, 2019