To get a good, healthy harvest from your fruit trees (including apples, pears, peaches, and plums) you need to thin the young fruit. This important step should be done when the fruit is smaller than a dime -- waiting much longer than this to prune will affect bud development for next year. Fruit is usually borne in clusters of two to six small fruits; you want to thin it to one large, strong, healthy fruit.
Look at each cluster. Here's what you want to remove:
- Wrinkled fruit
- Misshapen fruit
- Diseased fruit
- Fruit that is much smaller than the rest in the cluster
- Fruit with pest or disease damage