FIRE BLIGHT OF APPLE DISEASE

Описание: FIRE BLIGHT OF APPLE DISEASE
12.3 FIRE BLIGHT OF APPLE
Causal Organism: Erwinia amylovora
Symptom:
All above ground tissues including blossoms, fruits, shoots, branches, and in the root stock
near the graft union on the lower trunk are affected. Blossom clusters and young shoots:
The floral receptacle, ovary, and peduncles become water soaked and dull, grayish green in
appearance. Later shrivel and turn brown to black. Shoot symptoms: Tips of shoots may wilt
rapidly to form a "shepherd's crook”. Leaves on diseased shoots often show blackening along
the midrib and veins, before becoming fully necrotic. Numerous diseased shoots give a tree
burnt and blighted appearance. Droplets of milky coloured, sticky ooze may appear on
infected parts which usually turns brown on exposure to air.
Fig 12.3: Fair Blight of Apple
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Disease cycle:
Primary Infection: The bacteria overwinter at the margins of the cankers and possibly in
buds and apparently healthy woody tissue.
Secondary Infection: Insects such as bees, flies and ants spread the bacteria.
Favourable condition: Warm and Humid climate favours the disease development
Management:
 During winter pruning of blighted twigs, branches and cankers, and even whole trees,
at about 30cm below the point of visible infection.
 Disinfect the tools after each cut with 10% sodium hypochlorite.
 Insect control.
 Resistant varieties.
 Dormant sprays with copper sulphate or bordeaux mixture, however, Bordeaux
mixture or streptomycin are the only effective blossom sprays