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This article will help: https://www.gardeningknowhow.com/plant-problems/disease/fire-blight-remedies-and-symptoms.htm

If it is mature and healthy, there is not much you need to do for it but a little clean up pruning now and then, a yearly application of balanced fertilizer and watering it in times of drought.

Clean up pruning will consist of removing dead or sickly branches and thinning out branches that are crossing one another.

For bigger fruits, you may want to consider thinning the fruit in the spring, but if it is producing what you would consider adequate size fruit, you do not have to do this.

What a treat to get this question! We always hear about a lack of fruit not too much. This is why I love my pear tree. It offers such an abundance. Yes, you can remove some fruit. It won't be edible, but your remaining fruit will grow larger.

Could you send us a picture attached to this email That will help with identifying it.

Caterpillars and worms can typically be killed either by using Bt or neem oil, both of which are organic solutions. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/insects/prevent-caterpillars.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

This could be caused from some type of fungus. Treat the tree with a fungicide and see of this helps.