Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Apple -- Fire Blight
See Also: Pear -- Fire Blight
 
Symptoms: Several combinations of rootstock (M9 and M26) and cultivar ('Braeburn', 'Fuji', and 'Gala') are very susceptible to fire blight. Trees may collapse without any sign of disease in the canopy. Disease symptoms can be confused with Phytophthora collar rot. Symptoms have been observed around the graft union area. Infection may spread from the collar to the roots or from the roots to the collar. Cankers near the base of the trunk often appear dark, water-soaked, and purplish on the outside. The margin may at first be indefinite or raised and blistered but becomes definite and marked by a crack or crevice later. When the bark is removed, the cankered area may show red-brown streaking. The younger the tree, the more likely the tree will die following infection.

A "hold-over" canker on main trunk. This canker will remain here and provide inoculum for next year unless removed.

The classic "shepherd's crook" symptom where the tip of the shoot turns down when it dies.

Fireblight canker on apple branch.

Symptoms of fireblight on shoot tips.

Diseased branch not associated with flowers.

Bacterial ooze from infected branch.
 
Notes: Resistant rootstocks can be used and include G.16 and G.30 in the Geneva series and Budagovsky 9.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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