Q. Four years ago I planted several apple trees that are now starting to bear fruit. The apples they produced last year were numerous but small, and they had a lot of bad spots. In order to increase the size and quality of the fruit, what should I do?
A. Apple trees often set more fruit than they can mature to a good size and quality. If you permit all that fruit to stay on the tree until harvest time, you will wind up with a lot of small apples. Commercial orchards produce large, high-quality fruits by careful attention to thinning the crop and following a spray schedule to control disease and insect pests.
Apples naturally lose some of their abundant crop on their own. Some pea-sized fruit will drop after the flowers lose all of their petals (petal fall). These fruits usually have not been pollinated properly due to cool, rainy weather or poorly timed insecticide applications that interfere with bee activity. Late spring frosts can also damage the flowers to the point that the fruit aborts. There is a second drop from late May to early June. Commonly known as June drop, it occurs from competition among the fruits for water and nutrients. Hot, dry weather in spring can exacerbate it.
Although the amount of fruit that falls on its own might be alarming, you often need to do some additional thinning to get the larger fruit you desire. It is ideal to remove all but the largest fruit from each cluster and space the apples 8 to 10 inches apart on the branch.
While commercial orchards often rely on chemical thinning -- growth regulators or Sevin (carbaryl) insecticide -- hand thinning is a better choice for home orchardists. Chemical thinning does not permit the best positioning of fruit on the branch, and you can remove too many apples this way. Save the largest, healthiest fruits and remove the rest as soon as possible after June drop. In addition to increasing fruit size, thinning allows the tree to produce flower buds for next year's crop.
Some varieties will bear crops in alternate years if you do not thin out enough excess fruit. Thinning also protects the trees from breaking under a heavy load of fruit. Properly thinned fruit is exposed to more sun and better air circulation, which can help reduce disease problems and allow more even ripening. It is also easier to get good coverage with pesticide applications when fruits aren't hanging in clusters.
As for the "bad spots" in the fruits, there are many disease and insect problems that could be responsible. Follow a spray schedule through the growing season. Home orchard sprays are available that combine a fungicide and an insecticide so that you can control disease and insect problems with a single application. If you prefer to use botanical insecticides, companies like Gardens Alive! offer organic versions of combination fruit tree sprays.