Hi. It is difficult to say for certain what the issue might be without some additional close-up photos and perhaps even some samples. However, I suspect you may be dealing with a disease known as fire blight, which is a bacterial disease that commonly affects apples and pears. Ohio State University has a good fact sheet on the disease that you can read here. It is transmitted in the spring when the tree is blooming, often by pollinators but also by splashing rain and pruning. The bacteria infect new shoots and kill the vascular tissue, which causes the shoots to die. However, the leaves remain attached to the branch, as can be seen in your photo. As the disease progresses, it can move into older parts of the tree, which also seems to be evident in your photo. The branches in your tree that are affected appear to be long, unpruned branches that grew rapidly this and other seasons; that type of tissue is particularly susceptible to fireblight. The U. of Minnesota has a good fact sheet on growing pears here, and it recommends that new shoots be pruned to three feet or less on susceptible varieties. Fire blight is difficult to control. Next winter/early spring, when the tree is dormant, you should prune out all affected branches at least 4” below the dead wood to try to minimize the bacterial population. The wood should be burned or disposed of in the trash. During the summer, you should avoid applying excessive nitrogen fertilizer around the tree, since that will promote excessive growth. That could be happening if you apply a lot of fertilizer to your lawn, since the tree is surrounded by grass. The OSU fact sheet indicates that you can make an early season application of copper next spring to reduce the build-up of bacteria. You can also make several applications of the antibiotic streptomycin when the tree is blooming, though that is not recommended due to the risk of bacteria developing resistance. Spraying beneficial bacteria instead (Bacillus subtilis; available in Serenade Garden Defense) is a biological alternative described in that fact sheet. If you do decide to use any chemical sprays, be sure to read and carefully follow the label directions. You might also find this fact sheet on growing pears from Virginian Tech U. useful, which has similar recommendations to those of OSU regarding fire blight.