Differentiating Phytophthora ramorum and P. kernoviae from Other Species Isolated from Foliage of Rhododendrons

Phytophthora species are among plant pathogens that are the most threatening to agriculture. After the discovery of P. ramorum, surveys have identified new species and new reports on rhododendrons. Based upon propagule production, morphology, and colony growth, a dichotomous key was produced that can differentiate P. ramorum and P. kernoviae from other species known to be pathogenic to aerial plant parts of rhododendrons. These distinctions were made without molecular tools and wide-ranging variables such as propagule sizes and can be made without the need for a large culture collection.