Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of leaf blight caused by Phytophthora ramorum on cherry Laurel (Prunus laurocerasus) in Washington State, U.S.A.

Abstract

In April 2014, Phytophthora ramorum was recovered from symptomatic foliage of cherry laurel (Prunus laurocerasus) at an ornamental plant nursery in Washington State. Cherry laurel, also known as English laurel, is widely propagated in Washington State because it is commonly used in landscaping. It is invasive in forests near the urban/wildland interface in the western United States and in Europe. Given its popularity as an ornamental species, the potential of this host to spread P. ramorum is of regulatory concern due to possible long-distance spread to other states via nursery stock. Foliar symptoms consisted of dark brown lesions near wounds or around leaf margins where water collected. Shot-hole symptoms characterized by abscission zones and dropping of infected tissues were also observed. Lesions expanded beyond the margin of the shot-hole in some cases. Phytophthora was isolated from symptomatic foliage by surface sterilizing leaf pieces in 0.6% sodium hypochlorite and two rinses in sterile water. P. ramorum was identified based on morphological characteristics, molecular data (multilocus genotyping with microsatellite markers), and pathogenicity test. This is thought to be the first report of P. ramorum naturally infecting cherry laurel in the United States.