How is water core managed in the apple orchard? - Ask Extension
We have Prairie Spy apple trees with fruit that looks good on the outside but has a waxy, translucent flesh in part or all the apple. I'm wondering if...
Knowledgebase
How is water core managed in the apple orchard? #157299
Asked October 16, 2013, 2:30 PM EDT
We have Prairie Spy apple trees with fruit that looks good on the outside but has a waxy, translucent flesh in part or all the apple. I'm wondering if it's watercore. If so, how is it treated or managed in the orchard. Not all the apples are affected. We have other trees, Haralson, Sweet sixteen, Fireside, that are not affected by this condition. We did have 2 Northwestern Greening trees that also exhibited the same waxy flesh--those trees were lost in a 2008 hailstorm. I haven't found good information on "watercore". Appreciate any help or information you have available. I'll try to attach a picture.
Anoka County Minnesota
Expert Response
We have received a number of questions about this disorder. Here is a PDF link from the University of Wisconsin Extension Service-
http://fruit.wisc.edu/wp-content/uploads/2011/06/Watercore-of-Apple.pdf,
and a longer response from another Master Gardener that may answer your question
"It appears your apples have what is called Watercore. Watercore is a physiological disorder of apple fruit characterized by water-soaked tissue around the vascular bundles or core area due to the spaces between cells becoming filled with fluid instead of air. Affected tissue is water-soaked and glassy looking. Generally damage is not visible on the skin, and it is only when fruit are cut that the damage is seen. In severe cases flesh can be affected right up to the skin, which then darkens over affected areas. Some varieties are more susceptible to the disorder than others. These include Braeburn, Sundowner, Fuji and Lady Williams. Red Delicious and Granny Smith also are susceptible. Fruit with watercore are more likely to develop internal breakdown and alcoholic off flavors during mid to long term storage. While the cause of the disorder is only partially understood, it is thought to be linked to changes in membrane integrity associated with maturation and ripening. Apples with watercore have high levels of the sugar sorbitol in the intracellular spaces. There are several theories as to how this occurs, as sorbitol is not present in normal tissue. Low night temperatures in autumn and high day temperatures when apples are nearing maturity favor watercore. Low fruit calcium and high levels of nitrogen may increase the chance of watercore in susceptible varieties such as Braeburn, Red Delicious and Fuji. Over maturity at harvest and light crops of large fruit also favor the disorder.
There are two main types of watercore, each having a different range of symptoms. Block watercore occurs during summer on immature apples and radial watercore occurs on mature fruit.
BLOCK WATERCORE is characterized by translucent tissue, which originates from the conducting tissues near the core itself. It forms continuous flooded areas of flesh, which may extend to the skin (plate 1). Badly affected fruit can be recognized by darkening of the green skin or a darkening and high polish of red fruit. The lack of air in affected tissues may cause the cells to die, due to interference with respiration. If the tissues survive, they may recover whilst the fruit is still on the tree.
RADIAL WATERCORE occurs in ripening fruit. When affected fruit are cut across the center, a number of strips of watercore affected tissue can be seen radiating from the center like spokes of a wheel (plate 2). These strips run along the conducting tissue of the apple. The affected areas are often on the sunny side of the fruit, where there is more direct heat.
CONTROL There are no known cures for affected fruit. Picking fruit before watercore develops and at the correct stage of maturity will help reduce losses. Adequate calcium nutrition and careful use of nitrogen fertilizers can minimize damage in susceptible varieties.
http://fruit.wisc.edu/wp-content/uploads/2011/06/Watercore-of-Apple.pdf,
and a longer response from another Master Gardener that may answer your question
"It appears your apples have what is called Watercore. Watercore is a physiological disorder of apple fruit characterized by water-soaked tissue around the vascular bundles or core area due to the spaces between cells becoming filled with fluid instead of air. Affected tissue is water-soaked and glassy looking. Generally damage is not visible on the skin, and it is only when fruit are cut that the damage is seen. In severe cases flesh can be affected right up to the skin, which then darkens over affected areas. Some varieties are more susceptible to the disorder than others. These include Braeburn, Sundowner, Fuji and Lady Williams. Red Delicious and Granny Smith also are susceptible. Fruit with watercore are more likely to develop internal breakdown and alcoholic off flavors during mid to long term storage. While the cause of the disorder is only partially understood, it is thought to be linked to changes in membrane integrity associated with maturation and ripening. Apples with watercore have high levels of the sugar sorbitol in the intracellular spaces. There are several theories as to how this occurs, as sorbitol is not present in normal tissue. Low night temperatures in autumn and high day temperatures when apples are nearing maturity favor watercore. Low fruit calcium and high levels of nitrogen may increase the chance of watercore in susceptible varieties such as Braeburn, Red Delicious and Fuji. Over maturity at harvest and light crops of large fruit also favor the disorder.
There are two main types of watercore, each having a different range of symptoms. Block watercore occurs during summer on immature apples and radial watercore occurs on mature fruit.
BLOCK WATERCORE is characterized by translucent tissue, which originates from the conducting tissues near the core itself. It forms continuous flooded areas of flesh, which may extend to the skin (plate 1). Badly affected fruit can be recognized by darkening of the green skin or a darkening and high polish of red fruit. The lack of air in affected tissues may cause the cells to die, due to interference with respiration. If the tissues survive, they may recover whilst the fruit is still on the tree.
RADIAL WATERCORE occurs in ripening fruit. When affected fruit are cut across the center, a number of strips of watercore affected tissue can be seen radiating from the center like spokes of a wheel (plate 2). These strips run along the conducting tissue of the apple. The affected areas are often on the sunny side of the fruit, where there is more direct heat.
CONTROL There are no known cures for affected fruit. Picking fruit before watercore develops and at the correct stage of maturity will help reduce losses. Adequate calcium nutrition and careful use of nitrogen fertilizers can minimize damage in susceptible varieties.
-Patricia Fischer Wisconsin Master Gardener
I hope this is helpful information. Please contact AaE again if you have further questions.
I hope this is helpful information. Please contact AaE again if you have further questions.
