Fire blight is caused by the bacterium Erwinia amylovora and affects over 100 different plants. It’s generally more serious in Apple and Pear trees in orchards due to loss of production (technical information).
First symptoms appear in early spring with temperatures above 60°F when weather is rainy or humid. Tips of affected branches appear burned and take on the shape of a ‘Shepherd’s crook’.
“If you have noticed the “shepherd’s crook”, blackened and wilted stems during flowering, blackened flower parts hanging on to the tree well after bloom or slightly sunken darkened canker on the wood that may ooze cream-colored liquid you may have Fire Blight.”KATHLEEN V. SALISBURY – Penn State University
Some plants, like ‘Prairiefire’ Crabapple, are resistant to the disease.
Nitrogen is the primary plant nutrient that appears first on a fertilizer label, and the one that is known for pushing new growth. W.I.N. (water insoluble nitrogen) and organic sources of nitrogen provide more gradual release.
So, long story short, don’t get ‘burned’ by Fire Blight, go easy with the nitrogen on susceptible plants like: