The first signs of trouble usually show up during wet spring seasons when fire blight makes its appearance in the form of blackened blossoms and tips of branches that look as though they have been scorched by fire. The affected parts turn black, bend into a wilted position, and rapidly die back. Pear trees in spring are a feast for the eyes and a boon to beekeepers. The trees usually bloom late enough to avoid frost damage. There are so many agents helping to spread the blight bees and other insects, wind-blown rain, etc that there is no feasible way of preventing contagion.
Some authorities recommend spraying for blossom control and pruning to save the unaffected branches.
If the spring is a relatively dry one, spraying is helpful. In our area, spring is accompanied with plenty of rain either in the form of showers or storms, and spraying is a wasted effort. This year, for good measure, we re reaping some of El Nino s erratic behavior. As for pruning, my experience with blight-prone trees has been that I prune back more of the branches than grow in a season. Fire blight is a capricious disease.