At one time, the pear was a popular and widely grown fruit in the Midwest, comparable in importance to the apple. Fire blight has eliminated the possibility of commercial pear production in most areas of the Midwest. The fire blight bacterium can infect any portion of a susceptible plant. The common types of infection are blossom blight, shoot blight, and branch and trunk canker. Blossom blight is most common on pear, apple, hawthorn, mountain-ash, and Pyracantha .
Infected blossoms become water-soaked and darker green as bacteria invade new tissues.
The leaves wilt, die, and turn dark brown to black, usually remaining attached to the tree throughout the summer. As the bacteria move through the pedicel, the tissue becomes water-soaked and dark green. Infected tissues may exude either small droplets of a milky-white ooze or fine, hairlike strands containing millions of fire blight bacteria that can initiate new infections. The ooze, which later turns an amber color, contains countless bacteria that also are capable of causing new infections. Shoot blight is recognized by the rapid dieback of shoots.