Cedar-apple rust. Clip off and dispose of all affected fruits -- try not to get the orange dust which are SPORES on anything else. What I do is hold open a smallish plastic bag right under the fruits and clip off without touching the orange protuberances. You may also see yellow-orange spots on leaves. These will also grow the spore producing nodules on the UNDERSIDE while the spots kind of hump up. They should also be carefully discarded.
I keep a travel atomizer of rubbing alcohol with me and spray my hands and tools as I work. I also spray large cuts or other parts of the tree if it seems necessary ...or sometimes just because I feel like it. LOL
I only grow resistant varieties so the extent of damage is usually small and preventive sprays with milk solution and AACT (actively aerated compost tea) has been sufficient to keep things in check. But if yours is suffering quite a bit, you may need to use stronger antifungal measures. What variety of pear is it?
As the name implies, this fungus has a two year cycle, alternating hosts with cedar/ juniper trees. So if there are any nearby, you may be in trouble.
My next door neighbor had a very large cedar tree against the side of their house very close to my apple tree, but (luckily
) it succumbed to the cedar apple rust while my very disease resistant Enterprise Apple tree only suffered a few spotty leaves.
Unfortunately, my Serviceberry has turned out to be quite susceptible, and every year loses most of its fruits to this disease.