It sounds like it could be fireblight, a serious bacterial disease which pears are susceptible to. In the early stages you can manage it by pruning off infected branches; but when it gets to the trunk, there is no rescue and the tree will need to be removed.

Before doing anything drastic, you should have someone knowledgeable look at it. Check with your county extension office or a tree care specialist for help. I hope it is something else.

It does sound like fireblight to me after reading online about it. What could I use to spray it after I cut off all the dead branches?

There is nothing to spray that will control fireblight. Prune out and destroy all affected palnt tissue and try to make the soil the trees grow in as healthy as possible so the trees can fight off this bacterium.

Pruning out infected tissue is helpful--- if you can find it. New cankers that are developing from this year's infections are pretty hard to spot until they become next spring's sunken or cracked oozing lesions. But cutting out what you are able to see can help. You can also reduce infection by spraying a 0.5% bordeaux solution at bud break with two or three repeat applications until flower drop. That's because the pathogen is a bacteria that is largely vectored by honey bees. If a bee picks it up in one flower and drops it off in the next, on the same or a different tree, you can get another infection point started. If you can hit the bacteria with an antibiotic before it gets into the nectarthodes, you can prevent that new infection from happening. (It also helps keep down new infection points that pop up from rain splashing the bacterial ooze around and other insects picking up the ooze and moving it around the tree) Of course, If you hire someone they can use a more effective antibiotic than homeowners can buy. Back when I was an applicator, we had a lot of success with Agristrep. It's virtually impossible to eradicate the problem, but you can control it.

In My area the "Master Gardeners" are calling every pear problem Fire Blight. I have not found a single case where they were correct..... If it is fire blight there is a material (streptomycin) that can be sprayed on the tree before flowering & several times after that ALSO have use a spray of Copper Sulfate with good results There is also a "Moget" injection for fireblight which works well ... I say this meaning IF started 1st or 2nd year of problem..... By the way most of the trees around here are SUFFERING from damage caused by the late freeze we had. IF buds are full & IF wood is green there is a good chance your tree will come out of it & be well next year.... just fertilize & water

We have been living here for 6 years and these pear tree's are about 30-40 years old. The one tree is almost 1/2 dead. Branch, by branch it is turning black and dying. Last year it wasn't too bad and we trimmed all the dead branches. This year it's very bad and we have lots more to trim. The buds were full on both trees this spring, but we had no fruit at all. This is the first year that has happened and there was no fruit on either tree. I want to try and save them both and fear the one tree may be too far gone?

As Botanybob suggests, have your tree tested for fire blight. The symptoms you describe certainly sound like this incurable disease. It's better to know, for certain, what you're fighting against. Your local extension office will be able to help you with sample collection and might even have a pathologist on hand to help you.