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One problem that has been much worse this year in some tree than I have ever seen it is fireblight. It is always been a problem with fruiting pears but it has attacked some flowering pears and many crabapple cultivars with a vengeance.
Fireblight is caused by a bacterium and can seriously damage and even kill pears and some apple varieties. It also affects many ornamentals.
This disease is dependent upon the environment. It develops if conditions are warm and wet during blossom time. Spray with copper or streptomycin every three to five days while the tree is in bloom. Streptomycin is an antibiotic or bactericide, not an insecticide, and it will not hurt the bees.
This information is from Sherm Thomson USU Plant Pathologist (retired)
Fire blight symptoms are easily recognized by the scorched appearance of leaves, blossoms, and young terminal shoots. The initial infection causes wilt; infected tissue and tissue outward of infections then turns black on pear and brown on apple.
Blighted leaves remain attached to the tree through much of the dormant season. Infected terminals often exhibit a typical curling on the end, called a shepherd's crook.
A diagnostic symptom of fire blight infection is small droplets of bacterial ooze, light amber in color on infected leaves, flowers, and young infected terminals. Pear trees are generally more susceptible to fire blight than apple. Infection of pear flowers or terminals may progress into larger branches and even into the trunk to kill the trees.
Bacterial cankers form when the infection progresses into woody tissue. Cankers are slightly sunken areas with discoloration of the bark.
The bacteria overwinter on the margins of cankers. They begin to multiply and enlarge the cankers when the weather warms. The cankers can girdle branches and kill all growth beyond the canker. Droplets of ooze are exuded, each containing millions of bacteria. Insects such as flies are attracted to the ooze and transport the bacteria to flowers during later visits. They can survive in other rosaceous hosts such as pyracantha, hawthorn, cotoneaster and crabapple.
Infection of shoots usually takes place after blossom infection and then only on new succulent leaves and stems.The bacteria enter through natural openings such as stomates or wounds caused by hail, wind, or sucking-piercing insects. The tree is susceptible to infection until new growth stops. Root sprouts and trunk suckers are frequently infected and are serious since the disease can spread into the trunk or root system and easily kill the entire tree.
Any practice that promotes excessive succulent growth should be avoided. Trees should be fertilized to promote good health, but overfertilization with nitrogen or applications late in the season often cause too much new susceptible growth. Remove blighted blossoms and twigs as soon as they are evident.
