Last year's late-spring freeze destroyed both crops, resulting in an overabundance of developing fruit on trees this spring.
"Oftentimes when you have no crop one year, it sets you up in an alternate bearing cycle, especially on apples," said Michelle Warmund, University of Missouri tree fruit specialist.
When thinning peaches, leave one fruit every 8 inches. Thinning should be done before the peaches or apples reach the size of a dime.
Some peaches are fusing together like Siamese twins. This is a result of cold temperatures during pollination this spring. Such fruit is unsalable and should be thinned.
Some growers thin by striking the peach trees with rubber hoses, but this can result in a loss of leaves.
Apples usually grow five fruits in a cluster. Thin clusters to a single fruit to increase fruit size, boost the amount of sugar in each fruit and improve pest control, Warmund said.
"When you have five fruits hanging together, moisture collects between the fruits, making a good environment for disease," she said.
"If you have a tree with 500 apples on it, you have 500 small apples. All the sugars must be distributed among 500 fruits. If you thin down to 100, you get a much bigger fruit size," she said.
"The earlier you do it, the bigger fruit size you will have at the end of the season," she said.
Source: Michelle Warmund, 573-882-9632