Resolve problem with Cedar Quince Rust
What is the best way to stop cedar quince rust on my juniperus squamata and serviceberry? I planted two juniperus squamata in early spring without knowing that it could produce spores that would attack my serviceberry tree. The shrub and the tree are planted close together. In mid-June I discovered the serviceberry fruit covered with the fungi. There are also black cankers on the twigs of the squamata(Mr. Bowling Ball). I have pruned out all of the infected fruit and many of the branches of the serviceberry that had swellings. What I want to do is save the tree. What action should I take now? I know about spraying the tree with a herbicide next spring but will that stop the infectious cycle? Will it help to replace the juniper? What shrub could I use.? The shrubs must be compact and hardy. I'm in zone 7a(Taneytown, MD). The shrubs must endure harsh treatment as they are situated on the corner of my property at the intersection of two sidewalks. They are backed by a brick wall and the planting area is small. What's the best solution? Thanks.
The best recommendation is to select disease resistant plants. Unfortunately we could not find rust resistant serviceberries.
Here is a list of resistant junipers, crabapples, and hawthorns. There are many junipers that may be susceptible and some may not have been tested. http://articles.extension.org/pages/60612/table-of-juniper-hawthorn-and-crab-apple-resistant-to-rust...
The rust on the serviceberry is disfiguring but will not kill the plant. This can be common in cool wet weather. We are getting a lot of reports of rust disease this year, as our weather has been favorable for it.
Serviceberry is in the rose family, so it is susceptible to many of the same disease and insect pest problems that are seen in other species within the family (e.g. apples and pears). The alternate hosts of this disease are Eastern red cedars (Juniperus virginiana), Common juniper (J. communis), and Creeping juniper (J. horizontalis). The fungus carries out its life cycle between the two host plants.
It is up to you if you want to remove the junipers. However if there are other host junipers in the area this may not solve your problem as spores can travel up to several miles. This disease is very weather dependent and you may not have an issue next year. Here is our website on rust. It is up to you if you want to spray the tree next season. In general, we do not recommend chemical control for ornamental plants.