Canker
This is a disease presenting very serious difficulties, principally in the cultivation of Apples and Pears. Both the trees and fruits, especially of some varieties, are, in many localities, so far injured as not to be worth cultivating. What causes the disease is not at all times known; indeed, it is, in most cases, but imperfectly understood. Were the causes better known, the remedy might generally be much easier found. Some of the primary causes are cold and undrained soil, severe and careless pruning, extreme variations of temperature, and excessive growth, made late in the season, when it has not sufficient time to get well ripened. Trees that are badly Cankered may often be improved by lifting, and replanting in improved or better-drained soil. Immediately the disease is detected in young trees, by the cracking of the bark or the skin of the fruits, measures should be taken to find the cause, if possible, and avert its progress. Some Pear-trees, in various localities, will not produce fruit without Canker in the open garden, but they will do so when planted against a wall; and as such may be the very best varieties, trees should be placed in the latter position. The removal of large branches, late in spring, will sometimes produce Canker, at the point where mutilation has taken place; and it may be caused by severe late pruning, which induces the growth of soft shoots that are almost certain to be injured by severe frosts. The difference in the seasons, as regards the amount of moisture, is one that can scarcely be provided against. One spring may be favourable to rapid growth, and the following may be most unfavourable, thereby arresting the natural flow of the sap until the latter part of the summer, when excessive growth will probably take place. Such cheeks invariably produce Canker. At times, the disease seems caused by the punctures of insects, in an early stage, on the stems or branches. In such instances, a thorough cleansing, and a smearing of quicklime, made into a wash, often proves successful. Strong tobacco water will destroy insects, and a weak solution of sulphuric acid is also fatal to lichens and mosses, which should never be allowed to obtain a footing. The chief preventatives, therefore, are: Planting in well-drained soil; avoiding the use of any rank manure, to cause excessive growth; changing the old, or adding new, soil to injured trees; careful pruning, and the encouragement of early growth in spring, and subsequent well ripening in autumn.