Relative Susceptibility of Selected Apple Cultivars to Cedar Apple Rust and Quince Rust

Incidences of cedar apple rust and quince rust, caused by Gymnosporangium juniperi-virginianae and G. clavipes, were collected over several years from 1995 (23 entries) and 1999 (22 entries) planting groups of new apple cultivars and selections established at multiple locations. Cultivar Golden Delicious was the standard. Incidence of cedar apple rust on leaves and fruit and quince rust on fruit were analyzed. Only two analyses had significant cultivar × location interactions, suggesting differences within the cedar apple rust fungus. Cedar apple rust on fruit did not vary by location. Incidence of quince rust on fruit varied among cultivars by location. Incidences of cedar apple rust and quince rust on fruit were not related. Accepted for publication 16 August 2009. Published 14 October 2009.