What to look forFire blight affects many apple trees and pear trees. It damages cotoneaster, crabapple, hawthorne, mountain ash, ornamental pear, firethorn, plum quince and spiraea trees. Fire blight, caused by the blight bacterium Erwinia amylovora, can affect many parts of a susceptible plant but generally noticed first on damaged leaves.
Shoot blight occurs when infections begin at shoot tips, moving rapidly down the shoots and then to limbs and trunk. Apple and crabapple leaves turn brown, pear leaves turn black. Frequently, the tip of the blighted shoot bends over and resembles a shepherd’s crook.
How to treat fire blightPrune. Reduced Fertilization. Chemicals applications.
Control fire blight through pruning. Remove all stems showing symptoms as they first appear. Cut back into the healthy portion of both stems and limbs.
You can also control fire blight by making sure you do not over fertilize. Too much fertilizer will cause rapid new growth which is most susceptable to the blight. Moderate fertilizer to reduce rapid tree or shrub growth. Over pruning can have the same effect so you should refrain from heavy pruning.
Chemical sprays, although they have a negative stigma with use on trees that bear fruit we eat, will also do the job. The antibiotic streptomycin is the most effective spray material for controlling fire blight. It will prevent but not control infections. Use streptomycin in Spring during bloom.
To completely ensure fire blight won't wreck your crop, consider planting tree varieties that are resistant to this disease. There are resistant apple, pear, crabapple, ornamental pear and pyracantha trees. Check with your local garden center to find out which varieties they carry are fire blight resistance.