July 15, 2019
Pennsylvania plant owners have been warned to check for signs of infectious disease in rhododendrons they may have recently purchased.
The Department of Agriculture issued an alert Monday advising residents that rhododendrons received by retailers in 28 states may have been exposed to a plant pathogen called Phytophthora ramorum.
Officials said the pathogen causes infectious disease in a range of popular Pennsylvania plants and shrubs, from mountain laurel and lilac to viburnum and pieris. Its containment can be extremely difficult past the point of early detection.
Rhododendrons comprise more than 1,000 species of woody plants, including azaleas and pink "bow bell" evergreen shrubs. Their flowers are often pink, red, purple, yellow and white.
Signs of potential infection rhododendron owners should watch for are shoot dieback and leaf spots, though other problems common to these plants may mimic the disease. The best way to confirm the pathogen is through a lab test.
Phytophthora ramorum has at times been devastating to oak and other tree populations in California and Oregon. The pathogen, first reported in California in 1995, is believed to have been introduced to North America as an exotic species.