Hello,

Sprays for fungal diseases in pears begin with pear scab control in the green tip to pre-pink phenological stage. Fungicides work best as protectants before the plant is exposed to pathogenic fungi. Spraying during periods of low wind will help you to get good coverage where protection is needed while reducing drift. Reducing the initial fungal inoculum by early seasonal intervention is the best way to ensure that the fungal pathogen does not get established. Pruning out infected branches will also help to reduce recurrence of the disease. Above average rainfall will create a favorable environment for fungal diseases to thrive and may require additional applications within the specifications on the fungicide label.

Arborvitae (Thuja spp.) is not a host for rust diseases, including cedar apple rust and European pear rust. See this Ask Extension answer from 2020 for more information.

Do you have a picture of the rust on either the pear or the arborvitae?

I have an espalier pear tree on a west facing wall of my house. It’s been there about 4 years and growing ok. It doesn’t get a ton or full sun. Every spring it leads out and flowers beautifully and sets fruit. By about July I have rust and all the fruit drops. I’ve tried spraying fungicide and been oil but apparently not on an optimal schedule. Full disclosure I have arborvitae nearby. I spray those too in an attempt to control the fungus. To no avail. I’m not too concerned about the drop but would love the tree to look healthy through the summer.

Thank you for the reply. Attached are a few photos from different
years. The spots start around early July and by the end of the summer,
almost every leaf has spots. The arborvitae have never shown any sign
of rust or disease, but a garden center told me that they were a host
for the rust and I needed to treat both. So, good to know.

Is the stress from the disease causing the fruit drop generally? or is
there something I can do to help with that? I think I've harvested
about 5 pears (small) in the 5 years I've had the tree. It is grafted
and supposedly there are a couple of varieties I'm supposed to see. I
see some differences once fruit sets, but they all drop pretty much.

Thank you.


On Mon, Mar 27, 2023 at 4:30 PM Ask Extension <ask> wrote:
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Thank you for the reply. Attached are a few photos from different years. The spots start around early July and by the end of the summer, almost every leaf has spots. The arborvitae have never shown any sign of rust or disease, but a garden center told me that they were a host for the rust and I needed to treat both. So, good to know. Is the stress from the disease causing the fruit drop generally? or is there something I can do to help with that? I think I've harvested about 5 pears (small) in the 5 years I've had the tree. It is grafted and supposedly there are a couple of varieties I'm supposed to see. I see some differences once fruit sets, but they all drop pretty much. Thank you. On Mon, Mar 27, 2023 at 4:30 PM Ask Extension <ask> wrote: > ></ask>