Ask the arborist

Q: What are these orange growths on my cedars and serviceberry trees?



With the wet spring we had in southern Ontario this year, there has been an increase in the prevalence of Quince rust on serviceberry trees and shrubs. This fungus has a two-stage life cycle, the first of which is hosted on juniper or cedar species, and the second of which is hosted on species of the rose family. In the first stage, branches on infected cedars will swell up to double their normal size, and red-orange fungal fruit bodies will emerge out of the bark mid-spring.


The second stage of the fungus’ lifecycle will appear on both the fruit and the leaf of the serviceberry, and will cause damage to the twigs of the plant as well. The fungus will create orange colour spots on the leaves of the serviceberry and the fruit will appear smaller than normal with orange-to-white growths, like tentacles, surrounding it in early summer.


Serviceberry with quince rust


The easiest way to combat this fungus is to plant species from the rose family apart from cedar or juniper trees. If this is not possible, it is advisable to prune away infected areas of the serviceberry on a yearly basis and rake up and dispose of the infected leaves and fruit from around the tree.  These actions will disrupt the fungus’ lifecycle and thereby diminish its overall population. If left as is, the fungus can strangle branches and cause dieback after a couple of years.  Chemical treatment is rarely necessary, as minor management practices can help your serviceberry overcome the fungus.