This section of the book is from the Guide To Hardy Fruits And Ornamentals book, by Thomas Joseph Dwyer, published in 1903.
The San Jose Scale is a deadly fruit tree pest, minute in size inconspicuous in color, and remarkably prolific. It often escapes notice until it is present in dangerous numbers. This insect attacks trunks, branches, and even the fruit. If we begin spraying our trees when there is just a light sprinkling of scale there is no reason why we should not be able to keep it under control. We have been able to rid several country places of this pest, which have been under our supervision, with the following mixture: Twenty per cent. crude petroleum and 80 per cent, water, which should be applied in the early Spring just as the buds are beginning to swell; at that period the trees have a greater power to resist the penetrative qualities of the oil than during the winter months. The mixture should be applied in a thorough manner so that every particle of the tree will be reached.