Orange Rust on Pear Tree - Ask Extension
We have about 8 fruit trees, including 3 pears. One is showing orange spots on many of the leaves that match orange rust fungus. First time I've see...
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Orange Rust on Pear Tree #875535
Asked July 01, 2024, 4:06 PM EDT
We have about 8 fruit trees, including 3 pears. One is showing orange spots on many of the leaves that match orange rust fungus. First time I've seen this. We do have a cedar next door, by the way. I would have to remove many (most?) leaves to eliminate infected foliage. I've used "Serenade" to treat a different fungus on our Quince and it seemed to work, but would it work on this? But I've seen it said this is systemic, so once in the tree it's too late to treat - perhaps treatment is only effective early to prevent? I'd hate it to spread to our other trees or lose this one, wondering what should I do.
Thanks,
Frank
Multnomah County Oregon
Expert Response
Well, there are several different rust fungi that attack pear. Most cycle on some kind of conifer. If you have never seen this before then it could be the new rust called pear trellis rust. This one cycles on juniper not cedar. The one called Pacific Coast Pear Rust does cycle on incense cedars. Both are common these days. We manage the rust on pear in the spring and then on the cedar when spores are available on the pears. Here is info on the new rust: https://pnwhandbooks.org/plantdisease/host-disease/pear-pyrus-spp-trellis-rust-european-pear-rust
and on the other: https://pnwhandbooks.org/plantdisease/host-disease/pear-pyrus-spp-pacific-coast-pear-rust
and on the other: https://pnwhandbooks.org/plantdisease/host-disease/pear-pyrus-spp-pacific-coast-pear-rust
It doesn’t look like that new fungus because there are no growths on the back. Here are some pictures. What if anything should I do this time of year? What should I do next spring?
That is the one called Pear Trellis rust. The growths will occur this fall. It is interesting to watch them if you want. Depending on the severity you could just remove the infected leaves. The Juniper host is nearby somewhere. Removing that could also help but it might be in a neighbors yard and as such kind of difficult. Sprays in the spring are possible but I find most home gardeners are not able to spray thoroughly, on time and multiple times. Overall, it might not be a situation that needs control as the tree will continue to grow and you should continue to get fruit.
Thank you, this is helpful and encouraging. Sounds like it won't spread to other fruit trees from this one, rather will come each spring from the Juniper. So removing leaves may not have much impact - they don't seem so damaged that they aren't still working for the tree somewhat. I do see a Juniper about 100 feet away in a neighbor's yard - it looks healthy. Fascinating life history for a fungus to rely on two species like that.
Interesting that the affected tree has two pear varieties, and it's not affecting the Asian Pear half. Also not nearby Apple or Quince, but maybe just chance where spores landed .
Frank
