Apple trees can grow to a height of 30 feet and a width of 15 feet with a growth of 8 to 12 feet per year. They require rich soil, moderate watering, good drainage and full sun. When planting, space trees according to their ultimate size. To prevent corrective pruning later on, frequent light pruning during the tree's early years is required. It is recommended to prune mature trees to allow new growth and to permit sunlight to reach into the tree to discourage mildew. Scab is the most troublesome disease that affects apple trees. Fire blight, apple rust disease, black rot, and bitter rot can all be a problem as well as the following insect pests: aphids, red mite, flat-headed apple-tree borer, friot-tree bark beetle, codling moth, and apple maggots.