Determining Optimal Fruit Crop Load in Apple Trees
As an apple grower, determining the optimal fruit crop load in your trees is a critical step in achieving high-quality fruit and maximizing yield. Crop load management involves balancing the amount of fruit on a tree with the tree’s resources, including its size, vigor, and carbohydrate reserves. In this article, we will discuss methods for determining optimal fruit crop load in young and mature trees, as well as in high-density and low-density orchards.
Determining Optimal Fruit Crop Load in Young Trees
Balancing fruit load with vegetative growth is crucial for young apple trees to avoid “runting out” or biennial bearing, particularly for varieties like Honeycrisp. Even though some crop is desirable as early as the second year, it is important to limit the fruit load to prevent stunting the tree’s growth. To determine the optimal fruit load for young apple trees, you can measure the tree trunk diameter, usually about a foot off the ground, using the Valent/Cornell University Young Apple Thinning Gauge. The notches correspond to the recommended number of fruit or buds that should be left on the tree for ideal size and quality. The Cornell Gauge shows recommendations for both annual and alternate bearing cultivars. Another gauge available to determine fruit crop load is the Equilifruit disk. You can also use a caliper and measure the trunk diameter about a foot above the graft union. You can then use trunk diameter to determine the number of fruits per tree using Table 1, based on the Philip Schwallier and Amy Irish-Brown’s article “Predicting Apple Fruit Set Model”.
Determining Optimal Fruit Crop Load in Mature Trees
Measuring trunk diameter to determine optimal crop load is most useful for trees in their second to fifth leaf. However, once the trees have filled their allotted space, it is best to use the tree spacing and desired yield per acre to define the desired number of fruits per tree. This approach is mostly applicable to high density planting systems (e.g., to tall spindle). Table 2 provides recommendations on how to estimate target number of fruits per tree based on tree density, this table was also published in the Philip Schwallier and Amy Irish-Brown’s article “Predicting Apple Fruit Set Model”.
Although very time consuming another strategy to determine optimum crop load applicable to low density mature apple orchards is to use the thinning gauges or caliper on individual limbs. In this case, you would record the diameter of each limb, or use the crop load gauges to determine the ideal number of fruits per limb, and then you would add of the values to calculate a total number of fruits per trees.
