The malady known as Pink disease, due to the attacks of the fungus Corticium salmonicolar, has much more the appearance of what is commonly regarded as a canker. This disease makes its appearance as a pink incrustation covering the bark. The patch may extend until it covers a large area, in the centre of which the bark is dead and dry, whilst at the edges the advancing fungus is only superficial. Spores are formed upon the surface of the pink patch, and are carried by the wind until they find a lodgement upon the surface of the bark. This commonly occurs at a point where the trunk forks into two or more branches, and it is in such a position that the disease generally arises. Hyphae from the germinating spores penetrate into the bark and destroy its living tissue. From the centre thus established the disease then spreads widely over the surface.
The disease is readily recognisable owing to the pink colouration which it produces. When the fungus makes its appearance upon the upper branches of a young tree, the diseased branches may be cut off completely and burnt. On older trees, as in the case of canker, it is sometimes possible to cut out the diseased patch of bark, if the presence of the fungus is recognised at a sufficiently early stage. In South India the application of Bordeaux mixture is widely adopted as a preventive measure. The fungicide is simply painted on to the trees with a brush. This remedy is found to be effective, and the cost of application is small in comparison with the value of the immunity obtained. Bordeaux mixture is made by dissolving 5 lbs. of copper sulphate in 25 gallons of water in a wooden barrel, and pouring this solution into a large vessel simultaneously with a like amount of milk of lime. The mixture must be continuously stirred during the process. The milk of lime is prepared by pouring water very gradually upon S lbs. of quicklime, with constant stirring, the slaked lime being finally made up to 25 gallons. Theoretically, the amount of lime should be rather less than that of the copper sulphate, but in practice perfectly pure quicklime is not obtainable, so that some margin may be allowed.