Answer: Bradford pears will develop blackening of leaves from root stress problems (drought, too much water, root injury, etc). This is their form of leaf scorch. Fire blight is also a disease that affects Bradford pear.
Fire blight usually first appears during bloom. The blossom clusters wilt and turn dark brown or black. This is followed by twig blight infection of the current season's growth. The most obvious symptom of twig blight is a scorched appearance of affected stems in which the leaves wilt, turn brown, and cling to the stem. It is this stage that gives the disease the name "Fire Blight".
If you didn't notice any symptoms with the flowers earlier in the season, I suspect the problem is simply root stress.
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