Pear Tree Rust


my friend has a pear tree in his backyard in Brampton. it gets lots of sun. don’t know the soil type, its a rented house. the tree is affected with some sort of blight. please see the photos. can you tell us what it is and how to treat it and is the tree salvageable? thank you.


Thank you for contacting Toronto Master Gardeners.

From your photo it looks like what you have are blisters from Pear Trellis Rust. This is a fairly new disease in Toronto having arrived in the last few years. It is caused by a fungus, Gymnosporangium fuscum. All pear trees are susceptible to this disease with no known resistance in any of the trees.

The rust depends on another plant to complete its life cycle. In the fall when the blisters appear, the wind will carry spores from the blisters to nearby Junipers where it will over winter. In the spring it will again travel to the pear tree and begin all over again with orange spots on the leaves. These spots will mature and eventually end with the blisters like you have this year.

In the winter when it is on the junipers you will see:

  • Swelling or gall on branches in which the fungus overwinters.
  • Tiny, dark horn-like growths (telia), covered with an orange to orange-brown gelatinous mass protrude from galls.

From one of our earlier posts:  “Pear Trellis Rust alternates between pear trees (its summer host) and junipers (its winter host) this disease will almost certainly continue to cause your pear tree to lose its vigour as it is re-infected every year.  Even if you have no junipers in your immediate area, the spores of this fungus can travel up to 6 km on the wind, so the likelihood of continuing infection is strong.  You may be interested to read the Toronto Master Gardeners’ article on it:

The City of Toronto lists the following management practices for the Rust:

  • Attempt to maintain at least 10-1000 meters between juniper and pear.
  • Prune back and dispose infected branches from juniper in the fall and winter.
  • There is no registered pesticide in Ontario for control of this disease.




Good Luck