When infected early, the fruits remain small, become discolored, shrivel, and remain attached to the tree. On fruit, the symptoms depend on the stage at which the fruit was infected. On apple, it is common for the affected blossoms to cling to the spurs. The necrotic (dead) blossoms may or may not remain attached to the tree. One of the earliest symptoms of the disease occurs on flowers and is 'blossom blight.' The blossoms appear discolored (water soaked, gray-green color progressing to black). Secondary infections on young shoots are common following injury caused by hail, wind-blown dust, or insects.

Infected tissue turns brown to black, shrivels and droops, but remains attached to the tree. The infection moves from blossoms to young fruit and then to adjacent leaves. The bacterium enters the plant through blossoms, wounds, and natural openings (such as stomata, hydathodes, lenticels, and nectaries). In spring when the bacterium becomes active, wind-blown rain or insects spread it from oozing cankers to blossoms. During periods of high humidity, infected tissue may produce a characteristic ooze. Fire blight can infect blossoms, fruit, stems, leaves, and woody branches. The characteristic symptom of fire blight is that affected plant parts (most notably the branch terminals) appear to have been scorched by fire (fig 1). Other hosts include rose, quince, hawthorn, loquat, almond, apricot, plum, cherry, chokecherry, mountain ash, raspberry, blackberry, and strawberry. In New Mexico, the disease is most common on apple, pear, crabapple, pyracantha, photinia, and cotoneaster. Within this plant family, the bacterium infects at least 39 different genera. It affects only plants in the rose family (Rosaceae). In commercial orchards, spray with bactericide.įire blight, caused by the bacterium Erwinia amylovora, is one of the oldest known bacterial diseases of plants.Sign: Watery ooze produced from infected plant tissue. Key symptom: Branch tips turn black as if scorched by fire. Hosts: Plants in the rosaceae family, notably apple, pear, pyracantha, cotoneaster, and photinia. This publication is scheduled to be updated and reissued 2/04.Ĭausal agent: Erwinia amylovora, a bacterium. Goldberg, Extension Plant PathologistĬollege of Agricultural, Consumer and Environmental Sciences New Mexico State University.

Fire blight treatment