Trellis rust on Pear Tree

(Question)

I have 2 pear trees that look nice in spring but suffer every summer and fall from trellis rust, an ugly fungus that apparently overwinters in Junipers. The city’s ornamental ‘Chanticleer’ pear first showed it and later my dwarf fruit pear also became infected. Would removing all my junnipers help eliminate the trellis rust when my neighbour also has junipers 6 meters away? Is there a way to stop the fungus? I checked the City of Toronto website but it offered no solution. Thank you.

(Answer)

Pear Trellis Rust is becoming more and more common. It is a relatively new fungal disease in Ontario, first recorded in 2007. Unfortunately, it can be difficult to treat in urban settings, simply due to population density. It’s caused by the fungus Gymnosporangium sabinae that hosts in winter on junipers (although some junipers are resistant). In spring, the orange, gelatinous fruiting bodies (telia) emerge – usually after a rain – and mature to spread wind-borne spores over many kilometers. Some sources suggest the spores can carry for as much as 2-6 km. The spores alight on pear leaves, including those of ornamental pears, and then complete their spring and summer lifecycle – in their turn infecting or reinfecting junipers. And the cycle begins anew.

Advice is often to remove either the pear or the juniper, if they are spaced closer than 150 m (450 feet). In fact, the recommendation is to keep the two alternate hosts at least 1 km apart. within a 1-km radius.

The Ontario Ministry of Agriculture and Rural Affairs (OMAFRA) has an excellent fact sheet on Pear Trellis Rust.

http://www.omafra.gov.on.ca/IPM/english/tender/diseases-and-disorders/trellisrust.html

On the pear trees, it’s the leaves rather than the wood that play a role in the lifecycle of this fungus. However, do try to gather up and dispose of any fallen pear foliage and fruit; do not add them to your compost. One suggestion is to pluck them off the tree before they fall, but this is impractical for widespread infection.

While there are no fungicides specifically approved for Pear Trellis Rust, OMAFRA suggests that other fungicides might help minimize the impact on your trees. Look for those used to treat other Gymnosporangium rusts, such as cedar-apple rust.

If ever in doubt about a tree problem, it’s always wise to seek out a certified arborist for an on-site consultation. Try the Landscape Ontario website to locate an arborist near you. Click here.

Wishing you the very best of luck with your pear trees.