Excepting perhaps the codling-moth the scab is now the most destructive and widely spread drawback to apple culture and to a less extent of the pear. It is now so general in commercial apple-growing centres that every dealer and grocer in the Union is compelled to handle scabby Baldwin and most other leading commercial varieties. The fungus is first seen on the leaves in the form of smoky-brown patches. But it soon extends, changing the color and healthy expression of the foliage. The spores live over winter on the fallen leaves and on the branchlets of the trees. Hence it is advisable to plow under or to rake up and burn the leaves. In spraying it is usually advised to use the standard Bordeaux mixture (162. Spraying for Fungous Diseases) for the first as well as the after treatment. But the best results have come from spraying before the trees start growth with a much stronger mixture. Our practice has been to use six pounds of the sulphate to the milk of four pounds of lime, with water to make a total of fifty gallons.
After the blossoms have fallen the standard mixture may be used. In dry seasons the two treatments are sufficient with most varieties. But in neighborhoods where the scab is prevalent it is better to spray not less than four times, with intervals between of from ten to fifteen days.
The spraying for scab will also answer to keep down the bitter rot, powdery mildew, and to some extent the apple rust.