Phytophthora root and crown rot is caused by members of the genus Phytophthora, a group commonly known as water molds that affect over 100 of the most popular and desirable ornamental plants grown in North Carolina. Since Phytophthora is very difficult to control in the landscape through chemical management, knowledge of resistant plant species is the next best option; however, there is very limited information on which plant species and cultivars are resistant to the disease and can survive in soils with a prior infestation of Phytophthora.
In 2018, Meadows’ team evaluated 15 annuals and 12 herbaceous perennial plant species for resistance to multiple species of Phytophthora. Three landscape beds were established in North Carolina (Waynesville, NC; Salisbury, NC; Mills River, NC) and were infested with three species of Phytophthora known cause disease of nursery crops. Plants were rated for disease incidence and severity every two weeks throughout the growing season, and symptomatic plants were harvested and processed to determine the presence of Phytophthora and/or other common diseases that may have been suspected.