Beginner Gardening: Please help me solve this pear tree disease (Rust??), 1 by asish

asish wrote:
My pear tree which has 5 different kinds of pear varieties grafted onto the same plant has suddenly developed a disease that looks like rust disease.

Roughly about half the leaves have these kinds of spots that are shown in the attached photo.

I do not want to put any chemicals on the tree since the tree is fruit bearing.

Can you tell me what I should do to get rid of the rust spots on the leaf? Is this common? Where can I learn more about this - the causes and how can I prevent this in the future.

Thanks

Asish