Wednesday, August 15, 2012

Apples and pears beware ~ Fire Blight

Fire blight is a serious disease of apple trees and pear trees. This disease occasionally damages cotoneaster, crabapple, hawthorne, mountain ash, ornamental pear, firethorn, plum quince and spiraea. Fire blight, caused by the blight bacterium Erwinia amylovora, can affect many parts of a susceptible plant but generally noticed first on damaged leaves.

The bacterium, Erwinia amylovora, overwinters in trunk and branch cankers. In the spring, the bacteria resume multiplication when temperatures are above 65 F.

Disease symptoms are obvious which makes fire blight very easy to diagnose.  The name “fire blight” describes the most characteristic symptoms of this disease: a brown-to-black scorched appearance of twigs, flowers and foliage. It is usually seen first in Spring when blossoms and fruit spurs appear water-soaked, wilted, shriveled and finally turn brown to black.

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.

Disease Control:
A combination of pruning, reduced fertilization and chemicals can help control fire blight. Prune and remove all stems showing symptoms as they first appear. Cut back into the healthy portion of both stems and limbs.

Over fertilization 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.

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.

Resistant varieties to fire blight are apple, pear, crabapple, ornamental pear and pyracantha. You need to stick with these varieties when planting. Check your planting stock for fire blight resistance.

Trees "R" Us, Inc. is a professional tree service in the Chicagoland area.  We service the north shore, north suburbs and northwest suburbs of Chicago.  Trees "R" Us, Inc. has 4 certified arborists on staff ready to assess your plants and tree care needs in a timely manner.  Our services include tree trimming, pruning, stump grinding, emergency tree services, tree removal, cabling and bracing, fertilization and plant health care.

Trees "R" Us, Inc. can be contacted at 847-913-9069 or through our online forms at

Thanks for reading,

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