III.

Culture

Apple growing is a highly specialized business and the trend is toward larger orchards, especially because costly mechanical sprayers have been used to control diseases and insects. Leading diseases of apples are apple scabs, mildew, and fire blight. Insect pests include the codling moth, the apple maggot, the red-banded leaf roller, aphids, leaf hoppers, mites, San José scale, and oyster-shell scale. Rodents, particularly pine and meadow mice and rabbits, cause severe damage to trees unless proper control measures are employed.

Several horticultural methods are used in apple culture. One system is based on clean culture, with winter cover crops sown throughout the orchard; another method utilizes permanent sod and sod mulch. If a permanent grass or sod system is used, additional fertilizer is needed to compensate for organic nutrients absorbed by the grass. If clean culture is practiced, no additional cultivating is advisable after the first week in August, in order to permit the trees to harden off—that is, to become adapted to the lower temperatures of fall and winter.

Apple trees are vegetatively propagated by grafting or budding. By these methods a scion (bud of the desired variety) is inserted into the base of the stem or trunk of a seedling tree known as the stock. Sometimes the stock itself is a vegetatively propagated tree. Most trees are propagated, however, on seedling rootstocks. Several size-controlling rootstocks are available. Uniform heights facilitate spraying and harvesting. Extremely dwarfed rootstocks are popular where space is limited.

Most apple varieties require cross-pollination in order to bear satisfactorily. Certain varieties, known as triploids, are of no value as pollinators because of their genetic makeup. Two diploid pollinating varieties must be present to pollinate each other as well as the triploid variety.