Pear tree leaf rust problem

9 years ago

I live in the Pacific NW in Zone 8b. I usually get some orange-y spots on the leaves of my 10 year old pear trees, but it hasn't yet seemed to interfere with fruit production. However, the rust on the leaves is very widespread this year. I have done a little research online and have not been able to find very much info on ways to treat this. I understand this fungus gets passed back and forth between pear trees and juniper trees, but removal of the junipers is not an option because there are several of them on neighboring properties. Can anyone suggest some type of chemical treatment that would cure or at least diminish this?

Featured Answer

gardengal48 (PNW Z8/9)

9 years ago

"Certain other trees (that have similar looking foliage to juniper) can also harbor the fungus."

That is not correct. Only junipers are hosts to the various Rosaceae plants affected by this fungal issue. But they are not limited to just the eastern red "cedar" or Juniperus virginiana that gave the disease its name - various other juniper species can be hosts as well, many of them common landscape plants. This tends not to be a big issue here in the PNW. What does tend to be somewhat more common is pear trellis rust, Gymnosporangium sabinae. It tends to be rather common on pear leaves but appears much later in the season - like midsummer rather than spring - than does the very common cedar-apple rusts. And far less disfiguring to the fruit.

There is also a distinctly different but somewhat related disease, Pacific Coast pear rust/ aka cedar broom rust. It DOES have a non-juniper host, Calocedrus decurrens or incense cedar. These are native to the west coast and also pretty unique to this area. But no mistaking them for a juniper - these get to be huge trees of 40-60' or more!! This is far less common as incense cedars are not nearly as commonly or as widely planted as are junipers.

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Comments (7)

parker25mv
9 years ago
Are there any juniper bushes in the vicinity? That could by the problem.
kudzu9
Original Author
9 years ago
Yes. As I mentioned, several neighbors have junipers.
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parker25mv
9 years ago
You will need to continually spray Daconil and copper on the leaves. This is not to make the rust immediately go away but to prevent the tree from contracting rust in the future. This type of rust goes back and forth between the pear and the junipers to complete its lifecycle. It would also help if you made sure any other apple or pear trees in the area get sprayed, especially if they show any signs of rust. You are likely going to need to keep spraying for several years, with the fungal disease having established itself in the area. Best times to spray (in your climate) through March to May, and also late August to October. Typically spray every 1-2 weeks.

I'd also see if it is possible to spray all the juniper trees in the area with sulfur. Certain other trees (that have similar looking foliage to juniper) can also harbor the fungus.
kudzu9 thanked parker25mv
kudzu9
Original Author
9 years ago
parker-

Thanks so much. That all makes perfect sense.
clarkinks
9 years ago
Any fungicide rated for pear rust should treat it. Regular spray schedule will be needed.
kudzu9 thanked clarkinks
Mike Turner
3 years ago
One of you said to use daconil on pear! No sir! Daconil is NOT for pear