Hales (1727I 733) discussed the rotting of wounds, cankers, &c., but much had to be done with the microscope before any real progress was possible, and it is easily intelligible that until the theory of nutrition of the higher plants had been founded by the work of Ingenhouss, Priestley and De Saussure, the way was not even prepared for accurate knowledge of cryptogamic parasites and the diseases they induce.
But undoubtedly the most importapt of the woody excrescences on trees are cankers.
Such frost-cracks, sun-cracks, &c., may then be slowly healed over by callus, but if the conditions for necrosis recur the crack may be again opened, or if Fungi, &c., interfere with occlusion, the healing is prevented; in such cases the local necrosis may give rise to cankers.
It occurs in UK, but is not known to cause cankers.
However Q. robur and Q. petraea trees with oak decline do not usually exhibit bleeding cankers of the main stem.
Bacterial canker is spread by splashing rain and can cause rough cankers with amber colored gum, sometimes leading to total tree collapse.
cankers on umbra tree caused by Fusarium species.
The origin of the lesions was traced to basal stem cankers ca.
In native oaks in the USA, Phytophthora ramorum causes bark cankers.
A fungus was isolated from the leaf lesions and stem and stolon cankers.
First disease symptoms included chlorosis of the leaves as well as gum exudation through the cankers on the tree collar.
Such cankers often commence in mere insect punctures, frosted buds, cracks in the cortex, &c., into which a germinating spore sends its hypha.
It might well be maintained that the faults just enumerated were only cankers inseparable from every new and great movement, and that these excrescences would disappear in course of time, and the whole movement enter upon a more tranquil path.
Other potential diseases include leaf spot, die back, powdery mildew, cankers, and black knot.
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