Hello,

Control of rust disease on pear trees has a critical period of time in early spring. Thorough coverage of a fungicide spray repeated 2 to 3 times during the wet period of spring is important. Thorough coverage of the tree is also important.

You should also scout your area for junipers that show the second part of the lifecycle of rust disease. This second host of rust disease shows Juniper galls that can be pruned out and so reduce the rust spores in the area. You can also treat junipers now with a fungicide to reduce fungal infection on that plant. Or remove the junipers completely from the area. See the details in the link below.

Here is the paragraph describing fungicide treatment from the reference below:

“Fungicides have the potential to inhibit or minimize infections. Timing is critical. For example, spores are released from juniper for infection of pear during a two-three-week period in late April to early-mid June, at least according to observations over the past couple of years. Fungicides should ideally be applied before spore release and infection. Application of fungicides after the infection has taken place will be useless. Fungicides can also be applied to junipers to protect them from infection in the fall, typically late September to early October. Fungicides can be applied by cover sprays or by trunk injections… Thiophanate-Methyl and Chlorothalonil, and Propiconazole and Chlorothalonil.”

Here is a reference that describes the details of treating pear trees for rust diseases. Please note that any mention of brands or retailers in the article is for example and not an endorsement by MSU Extension.

http://www.gpwmi.us/Docs/Departments/DPW/Environmental/pear%20tree%20trellis%20rust.pdf

Here is another pear rust reference:

Kansas State:

https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Pear%20Rust.pdf

For the black spot issue:

I recommend you get a confirmed diagnosis from the MSU Diagnostic Plant Lab - Please send your leaf image that has the black spots to the MSU Diagnostic Plant Lab. The lab strongly encourages clients to email digital images prior to bringing or sending physical samples. Images can be sent to <personal data hidden>. There is a $20-25 dollar fee. Their website has the form and instructions: https://www.canr.msu.edu/pestid/

When you are ready to send a sample - Details of submitting a sample are at this link: https://www.canr.msu.edu/pestid/submit-samples/

Hope this helps!!