A bacterial disease, fireblight affects only members of the rose family. The infection enters through the blossoms, then spreads by pollenizing insects and splashing water from rain or sprinklers. Fire-blight is favored by temperatures above 60°F and high humidity caused by rain, dew, fog, or irrigation. The bacteria survive in blighted twigs and cankers.


Pear and quince are most susceptible; apple, crabapple, pyracantha, hawthorn, spirea, cotoneaster, toyon, and mountain ash are know to be damaged. 


Leaves, shoots, and developing fruit wilt and blacken as if scorched by fire. Dark, sunken cankers may form in large branches.


Streptomycin. fungicides, Pruning.


Prune off diseased growth, making cuts at least 6 inches below the infection on the smaller branches, at least 12 inches below blighted areas on the larger limbs. After each cut, disinfect pruners in a solution of nine parts water to one part bleach or rubbing alcohol. Apply a fungicide or streptomycin when about 10 percent of the flowers are in bloom; repeat at 4 or 5 day intervals until bloom ends.

Bonide Solutions