Thank you David for your question to "Ask Extension".  Your asian pear has a fungal infection known as Pacific Coast Pear Rust.  The fungus, also known as Gymnosporangium asiaticum, must reproduce using two hosts — making its life cycle unique.  It typically cycles from junipers to hosts in the rose family in early springtime, around the time that asian pears go through bud break.  
     Eliminating either host is the only practical cultural control. If the pear is the important plant, remove all junipers from a 1,000-ft radius.  There are no chemical controls for the home gardener.
    I hope that you find this information useful and as always Happy Gardening.

     Good sanitary practices should help reduce spreading of the disease. Pick up the dropped fruit and leaves.  Generally, you can place diseased plants (fruit and leaves) in the yard waste bin.  Commercial compostors reach a high enough temperature to kill pathogens.  Home composting is not recommended.  Overhead watering is also not recommended.  Being watchful of the other two scions would be a great experiment.  Again Happy Gardening.