Validation of the bait test with rhododendron leaves for Phytophthora ramorum

A bait test with leaves of Rhododendron ‘Cunningham's White’ and Rhododendron ‘Catawbiense Grandiflorum’ was validated for the detection of Phytophthora ramorum according to EPPO Standard PM 7/98 (2) Specific requirements for laboratories preparing accreditation for plant pest diagnostic activities (EPPO, 2014). The bait test was validated with zoospores and agar cultures as inocula for the parameters ‘frequency of leaves with necrosis’, ‘size of necrosis’ and ‘isolation rate’. In addition, the influence of the month of collection of bait leaves on the parameters was studied.