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Table: Diagnosis and Control of Fireblight
Pest Identification Host Plants Damage Symptoms
Erwinia amylovora
Apples, as well as other fruit and ornamental plants. Fireblight causes a blackening of the flowers, leaves, petiole, and branches. This blackening causes the tree to appear scorched (as if by fire) when multiple branches are infected. Older infections will form cankers on the branches and stem. In addition, blackened flowers and branches will bend over and curl. This curling is known as a shepherd's crook.
Monitoring Control Options Pesticides
Begin watching for fireblight infections in early spring during periods of wet weather. This is when the bacteria begin to produce ooze. Visual symptoms first appear on the flowers and then progress down the branch. Fireblight can be controlled through pruning and chemical sprays. Control should begin with pruning of blackened branches during late dormancy. However, susceptible trees may need to be pruned as soon as infection is noticed. Since the bacterium thrives on young succulent growth, avoid heavy nitrogen fertilizing, or practices that promote excessive growth. Finally a fungicidal spray should be applied. Bordeaux mixture can be applied as a dormant season spray, while streptomycin sulfate can be applied as a blossom spray. Bordeaux Mixture (copper sulfate)

Fire Blight Spray (Streptomycin Sulfate)

Description and Life History
Description: Fireblight is a bacterial disease that affects the flowers, leaves, shoots and branches of crabapples. This disease reproduces during periods of wetness producing bacterial ooze, which is a mass of bacteria and plant sap.

Life history: Bacteria overwintering in infected trees produce ooze during wet periods in the spring. This bacterial ooze is dispersed from infected plants to healthy plants by rain splash or insects. Bacteria infect the flowers and leaves of healthy trees through natural openings or wounds. The bacteria then multiply and spread through the branch toward the main stem.

Overwintering: The bacteria overwinter along the margins of old cankers.


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Last modified on March 06, 2013