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Fruit Cracking

Fruit cracking is often a physiological response to environmental conditions, such as irregular water supply. It’s common in the second part of the growing season that starts in July while the fruit is still relatively small and can go up to harvest.

Two other factors, boron deficiency and apple scab lesions, can lead to cracking as well. But, by far, the response to irregular water supply is the main reason for this phenomenon.

In order to understand how cracking happens, we have to consider that there is a set number of cells in an individual fruit. Those cells expand to accommodate and retain water absorbed through the skin and by the root system.

With sudden influxes of water and low rates of evapotranspiration due to high humidity and low wind, the cell walls will rapidly expand and stretch until they reach the breaking point. That breaking point is not the same for all apple cultivars. Different cultivars have different epidermal and sub-epidermal thicknesses. Cultivars with thicker layers are more resistant to cracking.

There are several other contributing factors to cracking:

  • Poor tree vigor – stressed trees that are suffering from malnutrition will not produce abundant foliage and strong flower buds. The fruit set on stressed trees is low, coupled with excessive fruit drop. Those trees will have poor growth resulting in reduced canopy size or a smaller surface for evapotranspiration that leads to increased fruit cracking.
  • Very late and hard pruning – can affect normal growth of foliage leading to overall reduction of surface area for evapotranspiration that results in fruit cracking.
  • Poor fruit set and/or over-thinning – few fruits left to absorb all the sudden, excess water can result in fruit cracking.
  • Apple scab infected areas – are not capable of cell division and expansion that results in cracked fruit.

Susceptible Cultivars

The most susceptible cultivars to cracking are Stayman, York Imperial, Wealthy, Fuji, Gala and Golden Delicious, mainly late in the season.

For Stayman and Wealthy, the cracks are found on the green cheeks as irregular lines that could be barely visible or extend deep into the flesh and circle the entire fruit.

The York exhibits numerous horizontal cracks, mainly concentrated around the fruit’s equator nearing ¼ inch deep.

When fruit is close to maturity, Gala and Golden Delicious cultivars develop cracks around the stem in the stem cavity.

The shallow cracks often heal and the fruit develops scars that resemble cork and deform the fruit. Deep cracks, especially ones on fruit near maturity, are attractive to many insects and susceptible to secondary pathogens that can lead to decay.

Prevention

What could be done to prevent this? There is not much we can do about the weather, but cultivar choice and tree care is in our hands. Avoid the crack-prone cultivars mentioned above.

Tree maintenance, such as pruning, fertilization, fruit thinning, and insect and disease protection, should be provided on a regular, timely basis in order to minimize fruit cracking.