Speck (apple)

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Tip on a large apple
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Stippe (also stippigkeit , in Middle Low German stip (p) e = point) is a deficiency symptom in apples .

Damage

Small, sunken, mostly pin-sized, brown spots can be seen on the shell. These spots are not only present on the skin , but also in the pulp below . In these places the pulp is also brown and somewhat corky and tastes slightly bitter. The symptoms of the speck sometimes only appear some time after harvest or intensify during storage and are therefore often discovered late - usually only when the apples are taken from storage for consumption. The apples can still be eaten without hesitation or processed into applesauce , for example .

root cause

The cause of specks is a lack of calcium in the fruit. However, there is often enough calcium in the soil. For example, the tree uses calcium for wood growth instead of fruit growth due to an excessively high nitrogen supply. Too much pruning can also stimulate the tree to grow heavily, so that the calcium is not used for the fruit. Calcium is also not absorbed in sufficient quantities due to an oversupply of potassium and magnesium in the soil.

More recent studies assume that the inadequate calcium supply in apple fruits is caused by insufficient perspiration. Calcium is mainly transported within the fruit via the xylem , while only extremely low concentrations are present in the phloem . A few weeks after flowering, when the apple's cell division has ended, or a certain degree of cell elongation has been reached, transpiration of the apple fruit comes to a standstill, which means that the xylem can no longer supply nutrients. The phloem transport, which takes place independently of the transpiration, still takes place, which is why nutrients such as potassium, magnesium and nitrogen can still get into the fruit. If the apple has not received a sufficient supply of calcium by the end of its transpiration, the risk of speckling increases sharply.

susceptibility

Large-fruited apple varieties such as Jonagold or Boskoop are particularly susceptible .

Countermeasures

The risk of specks can be reduced by pruning a tree , which counteracts both excessive shoot growth and too much fruit. Another possibility is the application of leaf fertilizers , such as calcium nitrate or calcium chloride . Since calcium can still be absorbed by the fruits after the harvest, the apples in many countries are immersed in a calcium solution after the harvest and rinsed off with water after 36 hours. In Germany, however, this form of post-harvest treatment is prohibited.

Web links

Commons : Bitter pit  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Defects in apples. Spotty is not rotten - SWR house guide
  2. ↑ A. Miqueloto, CVT Amarante, CA Steffens, S. dos Santos, E. Mitcham: Relationship between xylem functions on, calcium content and the incidence of bitter pit in apple fruit . Scientia Horticulturae, 165, 2014, pp. 319-323.
  3. ↑ High risk of illness with low calcium supply LW online, accessed on January 14, 2013
  4. ↑ KJ Scott, SE Hardisty, LA Stafford: Control of bitter pit in early picked Granny Smith apples from Western Australia . CSIRO Food Pres. Quart. 40, 2014, pp. 29-32.
  5. ↑ W. Dierend, S. Rieken: Post-harvest treatment of apples with calcium chloride . Commercial fruit growing, 49, 2007, pp. 51–56.