Cropload and hand thinning

Many crews are busy hand thinning apples to ensure that fruit is exposed to the sunlight and well-sized. In some cases, growers are trying to encourage return bloom as well, (although this response is greatest at bloom, and reduces as the season progresses). In the 2010 Cost of Production study, hand labour accounted for almost 20% of the labour hours, or about 24 hours per acre for mature orchards. This input has likely increased, as more growers focus on improved fruit size and colour, and recognize the benefit of hand thinning.

Fruit on the ground from thinning

Fruit on the ground from thinning

Cropload management on young trees is even more critical to ensure strong leader growth, a good balance of branch renewal and fruiting buds, and adequate fruit quality. Chemical thinning can be unpredictable in young trees, so most growers choose to rely on hand thinning. This task must be completed early in the season, and calculating the required number of fruit have become an important part of the cropload decision.

The Equilifruit Disk and the Cornell Young Tree Thinning Gauge are useful to carry in the orchard to determine how many fruit a young tree should carry. Use these tools to measure the trunk or branch by finding which semi-circle best fits. Then read the numbers beside the semi-circle to determine the correct cropload.

On the Equilifruit disk, there are 3 numbers by each semi-circle: the diameter in millimeters, the number of fruit (indicated by "F"), and the 'delta" number (shown in a triangle). The delta number shows the variation between cultivars. For example, on an 18 millimeter diameter branch, the F number is 15 and the delta number is 2. This means this branch can carry 15 fruit +/- 3, or a range of 12 to 18 fruit.

The Equilifruit disk

The Equilifruit disk

On the Cornell Thinning Gauge, there are 2 numbers for each semi-circle, an "H" number and a "G" number. In this photo, look at the largest semi-circle, and read below the numbers H182/G274. The smaller number (H182) represents the recommended final fruit count per tree for biennial varieties (eg. Honeycrisp, Fuji); the larger number (G274) represents the recommended crop load per tree for annual varieties (eg. Gala, Empire, McIntosh, Delicious). There are 10 semi-circles for various sized trunks, with corresponding H and G numbers. The gauge comes with instructions and is useful for larger trunk sizes.

The Cornell Young Tree Thinning Gauge

The Cornell Young Tree Thinning Gauge

For either tool, leave the desired number of fruit per tree by hand thinning, but only allow strong branches to crop.

For mature trees, this chart used for precision pruning in the spring may be useful to indicate how many fruits per branch are needed.

Orchard system Tall Spindle Slender Spindle Conventional
Yield goal
1500 bu/acre
1000 bu/acre
800 bu/ac
Tree density
1000 trees/ac
622 trees/ac
145 trees/ac
Tree spacing
11 x 4'
14 x 5'
20 x 15'
Yield per tree
1.5 bu/tree
1.6 bu/tree
5.5 bu/tree
Fruit per tree (100 count)
150 fruit/tree
160 fruit/tree
550 fruit/tree
Branches per tree
24
12
12
Fruit per branch
6-7
13-14
44-46
Buds needed*
12-14
26-28
88-92

*With insurance factor

Hand thinning can be a tedious job, but needs to be done correctly to achieve the results you want. Doing the calculations, and using these tools to keep on track will ensure the money spent on this task will return the benefits of fruit size, tree growth and return bloom.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca