Host Plants: Apple, flowering crabapple, pear, ornamental pear, firethorn, hawthorn, cotoneaster, quince, mountain ash.

Description: Fireblight affects a wide range of rosaceous plants including apple, flowering crab, pear, firethorn, hawthorn, cotoneaster, quince and mountain ash. Although fireblight can be a devastating disease, it is not as common in Kansas as scab and cedar-apple rust.

Symptoms of fireblight are most noticeable in the spring on blossoms and succulent new growth. Infected blossoms become water-soaked and turn dark-green or brown. Young, infected shoots rapidly wilt as if scorched by fire. The terminal end of the diseased shoot becomes hooked and is commonly referred to as a shepherd's crook. During wet weather, small droplets of amber-colored ooze containing millions of bacteria can be seen leaking from infected tissue. After initial infection of the shoots, the bacterium may move long distances within the living tissue and kill large portions of the tree. Infected areas of the bark on branches and trunks become slightly depressed and darker in color than surrounding healthy bark. When the outer bark is peeled away, the inner tissues appear red and water-soaked.

The bacteria overwinter in dead portions of the trunk or scaffold branches called holdover cankers. During wet weather in the spring, bacteria ooze from canker margins in gelatinous strands. The bacteria in the strands are splashed to flowers by rainfall or carried to the flowers by insects. The bacteria enter through natural openings in the floral parts. Infection is favored by wet weather and temperatures between 65 and 86 F. Honeybees visiting diseased flowers become contaminated with the bacteria and spread them to adjacent healthy flowers. Shoot infection may also occur at wounds caused by pruning cuts or hail injury.