My pears have rust, what can I do?

Two small pears with rust
Photo credit: Ask an Expert

Last year crop was a total failure due to this. This year I have gently removed close to 6 small fruit starts. I just found some leaves on the pear with these spores. I have been treating the soil and the tree with neem granules, for soil, and neem oil spray for leaves and branches and fruit. Spraying about every 2 weeks. Still not under control. Please advise on any other methods besides cedar tree removal. I haven't found any cedars close by with this rust yet. But I believe a western red cedar in the adjacent yard was orangish in color about 2 years ago. Looks bright green now. 

- Washington County, Oregon

Yes, your pear tree is infected by Pacific Coast Pear Rust. (If it's any consolation, many other pear trees in our region also have rust this year.) Significant outbreaks occur every several years. Both Asian and European cultivars are susceptible. 'Winter Nellis' is severely affected whereas 'Bartlett' is typically less affected. Some years, ‘Bartlett’ can also be seriously affected.

Most rust diseases are interesting in that they require two hosts to complete the life cycle. With Pacific Coast Pear Rust the alternate (2nd) host is incense cedar.

At the time pears were in flower, bright orange telia (jelly-like blobs; the fungus) were on the infected cedars. (See attached image.) Airborne spores from the jelly masses infect susceptible pears, both flowers and leaves.

In order for a spray to be effective, it must be applied when the swollen, orange telia are present on the cedars. In western Oregon, that’s usually during bloom. (In other words, it’s too late to spray this year.)

Another glitch is that suggested products are available only to commercial pest control companies. (If you may hire a company, consider reviewing “Selecting a Pest control Company”.

Do not apply pesticide to the soil. It won’t affect rust.

Your strategy for the remainder of this year will include (1) good sanitation (collect and discard infected leaves and fruit); (2) remove and discard any infected woody parts; and (3) if the incense cedar is on your property, consider removing it.

Jean R. Natter
Master Gardener Diagnostician
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