This week’s fungus, Cedar-Quince Rust. Cedar-quince rust is caused by the fungal pathogen, Gymnosporangium Clavipes. This fungus infects a wide range of plant material; plants in the rose family such as hawthorns, serviceberry, and crabapple. Eastern red cedars and junipers are evergreen hosts. Pictured in the photos are infected carpet junipers.
On evergreen hosts, infection occurs on needles and new shoots. In damp spring weather, orange, gelatinous blisters burst through the bark where the branches are swollen. Most people do not notice the branch swellings until they observe the bright orange color on the twigs. Cedar-quince rust disease damages the ornamental value of infected cedars and junipers as most of these swellings girdle and kills small twigs. When infection occurs on the main trunk it will weaken the entire plant. Some plants may survive and remain infectious for many years.
There are some strategies for controlling Cedar-quince disease. Sterilize pruning to remove infected branches can be performed. Protective fungicides can be applied to the infected plant to reduce further infection. Treatments should be performed annually.
