Gymnosporangium-rust of Rosaceae, Juniper-rust – Gymnosporangium sp.
Symptoms / species
Impact / measures
Pears: leaves in summer on the upper surface with orange-red spots, lower surface with felty excrescences; Crataegus, Sorbus aucuparia, Cydonia, Mespilus, Chaenomeles, Malus and others: leaves with red, yellow or brown spots; juniper: yellow-orange or brownish, jelly-like extuberances on the stem and on branches, attacked parts often swollen.
Affected tree species
Apple; Common medlar; Common whitebeam; Cotoneaster; European mountain ash; Hawthorne; Juniper; Juniper cultivars; Pear; Serviceberry; Wild service tree;
Leaf; Needle; Stem; Shoot/Twig/Branch;
Several species of the rust genus Gymnosporangium with host alternation between juniper and various Rosaceae. Junipers sometimes suffer from branch dieback, Rosaceae(esp.pears) from loss in fruit yield; generally not life-endangering. Further information (in German): Gehölzkrankheiten in Wort und Bild (TUM Weihenstephan).
Curative measures Control mostly not necessary; in orchards preventive fungicide treatment of the main host (Rosaceae) in spring (see official register of Plant Protection)