Links to recent or useful information on rust diseases (in addition to photos further down on this page):
2016: Rust Diseases of Apples and Pears. This article in Scaffolds Fruit Journal reviews the six species of rust diseases that can occur on apples and pears in the Northeastern United States and measures for controlling them.
2005: Susceptibility of New Apple Cultivars to Rust Diseases in Southeastern NY.
This poster provides assessments of susceptibility to cedar apple rust, quince rust, and hawthorn rust in graphic format, along with some photos. (This is a very large file, so it may take a while to load). Most of the data shown in graphics on this poster were presented in tables, along results of statistical analysis, in the 2003 Fruit Quarterly article listed below (see the next link).
2003: Susceptibility of New Apple Cultivars to Common Apple Diseases. Publication in New York Fruit Quarterly.
Photos of Cedar apple rust on apple fruit and leaves:
Rust-induced leaf spotting on apples: Cedar apple rust infections may fail to develop either because they are arrested by fungicides with post-infection activity or because host-resistance in some cultivars prevents further development. However, the rust spores germinating on apple leaves apparently kill or injure some of the leaf cells, and these compromised cells are subsequently invaded by secondary pathogens such as Phomopsis, Alternaria, or Botryosphaeria species that cause leaf spotting. In some cases, the leaf spotting can cause as much leaf damage as would have occurred if the development of the rust pathogen had not been impeded.
Rust-induced leaf scorch: When apple trees are exposed to high concentrations of rust spores, some leaves develop a generalized leaf yellowing (upper left photo below) that is independent of the appearance of rust lesions. Scorch refers to development of necrotic leaf tissue either along leaf edges or between veins, and it appears in late May or early June on leaves that were severely compromised by rust and may occur even on cultivars that are considered resistant to the development of cedar apple rust. Leaf scorch may result from invasion of leaves by secondary pathogens or from phytotoxicity caused by other pesticides that are absorbed into rust-damaged leaf tissue.
Cedar apple rust on cedars:
Quince rust on apple fruit:
Quince rust on apple fruit stems: Photos taken shortly after bloom in 2005 in a variety trial at the Hudson Valley Lab where apples were planted close to cedar trees. Infections on fruit stems will cause the fruitlets to abscise and can result in total loss of the crop.
Quince rust on cedars:
Quince rust on quince and pear fruit:
Pear trellis rust on pears (photos courtesy of Margery Daughtrey, Long Island Hort Reseach Center):
Updated 13 June 2017