Fireblight attacks growing tissue so the only time we are really safe is winter. That’s important because canker in stone fruits like cherry, peach,and plum is always active. The bloom stage for pears is very dangerous because the blooms grows very rapidly and insects go from bloom to bloom spreading the disease. Fireblight is at its height when its wet and warm. 65 degrees give or take and 65 percent humidity give or take is perfect fireblight weather so for us that’s spring. Our summers July and August are hot but dry so FB does not spread much. Insects eat foliage and birds fly tree to tree so don’t rul it out. Like Olpea said spraying antibiotic past bloom won’t help and once the fruit develop the tree sealed those open flowers. Open wounds and fast growing tissue are the things to watch for now. FB strikes typically tips of branches during this time and amputate below those strikes as fast as you can.