Pest survey card on Chrysomyxa arctostaphyli

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M2020-0114), at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for surveys for Chrysomyxa arctostaphyli, the causal agent of spruce broom rust. Chrysomyxa arctostaphyli is a well-defined and distinguishable fungal species of the genus Chrysomyxa (Uredinales, Coleosporiaceae) and a Union quarantine pest currently not known to occur within the EU. The pathogen is rust fungus with a two-year life cycle alternating between two systematically distinct hosts: the aecial host Picea spp. (spruce) and the telial host Arctostaphylos spp. (bearberries and manzanitas). The natural spread of C. arctostaphyli is through wind-borne aeciospores and basidiospores from the aecial to the telial host and from the telial to the aecial host, respectively. The spread can be facilitated by human activity through the movement of infected host plants. Should C. arctostaphyli be introduced into the EU, climatic conditions will not be a limiting factor to pathogen establishment, and both hosts are widely distributed (spruce occurs naturally, as an ornamental and forestry plantation tree) and often found associated in the same habitats. Detection and delimiting surveys of C. arctostaphyli in the EU should target all susceptible Picea and Arctostaphylos species located within a distance of 300 m from each other. Chrysomyxa arctostaphyli is detected in the field through visual observation of symptoms on both host plants (conspicuous, perennial brooms on Picea spp., purple-brown spots on one-year-old leaves of Arctostaphylos spp.). Nevertheless, the identification of the pathogen needs to be confirmed in the laboratory by observation and description of the morphological characteristics of the pathogen and by the use of molecular diagnostic techniques of PCR.