In our own practice we found nothing better than linseed oil for cleaning bark of scale, but some have complained that it killed their trees. Perhaps where there is this risk the following from the Gardeners' Chronicle may be preferred :

"Now is a good time for cleaning any trees that may be infested with scale or mealy-bug. The following mixture may be used: - 2 oz. of flower of sulphur, 2 oz. of soda, 1/2 oz. of shag tobacco, and a small quantity of lime, put in a saucepan and boiled in a gallon of water for a quarter of an hour. Allow it to settle, pour off the clear liquid, and therewith syringe the trees well once or twice during the winter. It will keep good for any length of time. I have also used parrafin mixed with water, say a wineglassful to a gallon of water. This will clean the trees if repeated while growth is at rest. Another plan that I have found to answer, is to syringe the trees four or five times with strong manure water as collected in a tank from the cow-shed".