Fruit Removal Where No Fruit Is Desired
Apples and Crabapples
Florel (3.9 percent ethephon), marketed by the Union Carbide Company, and the insecticide carbaryl (Sevin) have fruit removal and growth regulator effects on apples and on some crabapple varieties. Many garden stores sell both products.
Florel. Early in the blooming period, spray the trees with a solution containing 21⁄2 to 3 fluid ounces of Florel per gallon of water. Use the higher rate if the weather is cool. Apply enough spray to wet thoroughly all the blossoms and leaves. Florel is not as effective when applied at petal fall (when most of the petals have fallen) or later. It is also not very effective on small, red-fruited varieties of crabapples.
Carbaryl (Sevin). This chemical is most effective when applied at petal fall. As the young apples grow, they become more resistant to the effects of carbaryl and are almost completely resistant to it about 20 to 25 days after petal fall.
Apply carbaryl (50 percent wettable powder form) at the rate of 3 level tablespoonfuls per gallon of water. Do this at petal fall and be sure to wet the young fruit and leaves thoroughly with the spray mixture.
Carbaryl is toxic to bees. Therefore, it should not be applied until most of the petals have fallen. Spraying at dusk will further minimize the risk of killing bees, especially when the petals still remain on a few later flowers.
The thinning action with carbaryl should begin to be apparent 7 to 10 days after application. By that time, affected apples will stop growing, their stems and seeds will turn yellow, and the fruit will start to drop. Fruit drop may continue for 7 to 10 days. If needed, a second application of carbaryl can be made 10 to 15 days after the first application.
Note that apple varieties differ in their response to the fruit removal action of carbaryl. In general, fruit removal is more successful on the fall and winter varieties than on the summer ones.
Mechanical Method. When the young apples are about 1 inch in diameter, vigorous shaking of the branches will remove much of the fruit.
Apricots, Peaches, and Plums
No chemicals are registered for fruit removal on apricots, peaches, or plums; therefore mechanical methods are suggested.
About 4 to 7 weeks after the blooming period, the fruit goes through a phase of about 2 weeks duration in which the attachment to the tree is not as tight as it was earlier or will be later on. In other words, the fruit is loose and can be removed more easily by jarring the branches. The fruit is approximately 1 to 11⁄2 inches long during this loose period. But when the pits start to harden, the fruit attachment becomes stronger.
Grab a branch and shake it vigorously, using short strokes, or give the branch a sharp blow with an instrument that will not cause injury to the bark. Toy plastic bats, used to hit hollow plastic balls, are useful on smaller branches. An 18-inch-long piece of stiff rubber hose nailed to a broom handle can also be used. Only hit the branch with the rubber hose portion of this device.
Cherries and Mulberries
There is no practical method for the removal of young fruit on cherry and mulberry trees.
No chemicals are presently labeled for fruit removal on pears. However, vigorous shaking of the branches when the fruit is about 1 inch in diameter will remove much of the fruit.
Fruit Thinning Where Fruit Is Desired
In addition to their ornamental value, fruit trees that are cultured for fruit production frequently re- quire some fruit thinning. Excessive crops of apples, peaches, pears, plums, and apricots result in small- sized fruits of inferior quality. In addition to reducing fruit size at harvest, excessive fruitset retards the development of fruit buds for the next year’s crop. Bro- ken branches, distorted tree shapes, and every other year bearing cycles may also result.
The decision to thin fruit on a tree is always difficult to make, even for experienced commercial growers. Home gardeners who are hesitant to thin fruits are encouraged to use this procedure on a few selected branches. They can then make a direct comparison of fruit quality with those produced on the unthinned portions of the tree.
Chemical Thinning of Apples
The insecticide carbaryl can also be used for the selective thinning of apples by modifying the concentration and timing.
Summer varieties are relatively difficult to thin. Therefore, carbaryl should be applied at petal fall. Use 2 level tablespoonfuls of carbaryl 50 WP per gallon of water and apply so that the entire tree is wetted thoroughly.
On ‘Golden Delicious,’ ‘Red Delicious,’ and other fall and winter varieties, delay applications until the largest of the young apples are 1⁄2 inch in diameter.
Then spray thoroughly with 2 level tablespoonfuls of carbaryl 50 WP per gallon of water.
Chemical thinning rarely gives perfect results. It may be necessary to follow up with hand thinning once the apples reach 1 inch in diameter.
Shaking and Pole Thinning of Peaches, Plums, and Apricots
Careful mechanical shaking or branch jarring when the peaches, plums, and apricots are in the loose stage will remove some fruit without removing all of them. (See the section on “Apricots, Peaches, and Plums” for a discussion of this method.) Start with gentle shakes or hits and gradually increase the intensity until sufficient fruit are removed.
Hand Thinning of Apples, Pears, Peaches, Plums, and Apricots
Selective hand thinning is the only method suggested for pears. It is also recommended for the final thinning of apples, peaches, plums, and apricots.
Following the normal “June drop,” when the fruit is 1 inch or more in diameter, thin apples, pears, and peaches to an average spacing of 6 to 8 inches apart. For example, if there are two apples on a 12- to 14-inch-long branch, leave both fruits, even if they are close together. However, if such a branch has more than two fruits, remove all except two.
Thin plums and apricots to an average of about 3 inches apart. Delay plum thinning until the latter part of June.
Hand thinning enables one to remove and discard small, misshapen, damaged, and diseased fruits. Leave only the largest and healthiest specimens on the tree.