Our wet and warm May conditions were favorable to widespread fire blight in Boulder County. Consider pruning now to manage the infection and burn or remove cuttings from site.
Symptoms of fire blight are first seen about the time of petal fall. Infected blossoms appear water-soaked and wilt rapidly before turning dark brown; this phase of the
disease is referred to as blossom blight. As the bacterial invasion progresses, leaves wilt, darken and remain attached to the tree; this gives the tree a fire-scorched appearance, thus the name “fire blight.”
Infected twigs darken and branch tips may bend over forming a “shepherd’s crook.” During wet conditions infected tissue may exude creamy bacterial ooze in droplets or fine, hair-like strands. Infected fruits also exude bacterial ooze. Rather than dropping from the tree, infected fruits gradually dry and remain attached to the branch.
Fire blight cankers on branches or stems appear as dark discolored areas that are slightly sunken, with a narrow callus ridge along the outer edge. The narrow callus ridge is diagnostic for differentiating fire blight cankers from fungal cankers. Under the bark associated with a canker, the inner bark turns from green to brown, but the appearance varies depending on plant variety. Droplets of bacterial ooze may appear on the canker.
There is no cure for this disease, so prevention is the best solution for the management of fire blight. Fire blight management methods include: planting resistant varieties, implementing cultural practices that favor growth of the plant rather than the pathogen, pruning to remove infected plant parts, and chemical sprays. Using resistant varieties is the most effective prevention method.
Please click for more info in this factsheet and excerpt: http://extension.colostate.edu/topic-areas/yard-garden/fire-blight-2-907/
For more commercial approach to management, see:
For more information call or vist Colorado State University Extension, Boulder County, 9595 Nelson Rd. Box B, Longmont, CO 80501, 303-678-6383.