Seasonal symptom expression, laboratory detection success, and sporulation potential of Phytophthora ramorum on rhododendron and camellia

Camellias and rhododendrons are important nursery and landscape plants and are known to be highly susceptible hosts of the quarantined plant pathogen, Phytophthora ramorum Werres, de Cock & Man In?t Veld. Nursery inspection can not always occur during optimal conditions for the disease and its detection. The goals of this research were to (1) characterize and document seasonal development of symptoms, including, lesion growth rates and host leaf abscission, (2) evaluate the USDA-APHIS approved laboratory detection methods during four seasons, and (3) access the seasonal potential for sporangial or chlamydospore production on lesions. This paper contains the results of the first complete year of a two year field and laboratory study.