Serviceberry rust


We have a problem with rust on our serviceberry bush. The bush is about 3 years old. The rust is visible in the spring & continues through the summer.
Is there anything that we can do to get rid of this.
I tried to attach a photo but the file is too large


Serviceberry is susceptible to rust fungi that turn the leaves a rusty-orange colour or results in rusty-looking lesions on the leaves.  The fungus requires 2 hosts living in relatively close proximity — juniper and your lovely serviceberry. These rusts generally do not harm the plant, they just make it less attractive and the berries often are also affected, so should not be eaten.  The wet spring and ongoing wet summer we’ve had (it’s now the end of August 2023) have likely stressed your plant and contributed to emergence of the fungi.

You can remove afflicted branches, berries or leaves and dispose of these in the garbage (not compost).  Or you can choose to put up with the rust and leave the bush alone.  Refrain from over-head watering, to keep the leaves as dry as possible. And keep in mind that if we have a relatively dry spring/summer next year, the rust fungus will likely not be so aggressive!

The fungi over-winter on branches and galls that are found on junipers and red cedar trees. In the spring, these nasty galls produce gelatinous orange growths that release spores, which are released into the air and carried by the wind to infect your serviceberry.  These trees may be a few kilometres from your serviceberry, but usually will be found within a few hundred metres.  If you wish, in late winter or early spring, inspect nearby juniper and red cedar trees – look for and prune out the brown, woolly galls.  This step will help control the fungal infection on these plants, and later on your serviceberry.   Discard these in the garbage (not compost).

If the entire bush is covered in fungus, it may be unhealthy and you may wish to pull it up and discard it (again, in the garbage).  If this is the case and you wish to replace your serviceberry with another, there are some varieties that are marketed as having “improved” rust-resistance.  It’s not clear how rust-resistant these bushes are – I’d suggest speaking with your local garden centre.

A couple of previous responses posted on our Ask a Master Gardener website provide helpful information about rust:

  • Serviceberry blight, Part 2 – The Missouri Botanical Garden link in this post has a good section on what to do to manage the fungus.  Note the updated link to Cornell University’s Cedar-Apple Rust.  For additional information on how to manage the rust fungus, see also University of Minnesota Extension’s Cedar-apple rust and related rust diseases
  • Edible garden – spikes on serviceberry fruitsThis response provides additional details about rust, including how to control it, with a link to the very limited number of fungicides permitted for use in Ontario. Generally fungicides are not recommended for use by home gardeners, as they can harm pollinators, birds and wildlife.

I’m assuming that your serviceberry is indeed suffering from rust.  However, there are a number of diseases and pests that can affect the plant. See the Connecticut Agricultural Experiment Station’s Shadbush, Serviceberry (Amelanchier) – Plant health problems.  I’m bringing this to your attention as as a previous client asked about serviceberry rust, yet described a likely case of fire blight (discoloured, curled leaves with dark spots). Fire blight is a bacterial disease that can infect the plant, but this would make the plant tissues look burned and the leaves would look shrivelled — not rusty.

All the best in keeping your serviceberry healthy!