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The term pocket or junk disease has its origins in the "crazy" look of the fruit ('fools'). The term 'Tesche' or 'pocket' comes from the Middle High German language and means something like 'foolish woman'. The affected fruits are also referred to as scallops or prawns.
Reasons for the infestation with the fool / pocket disease
The pocket / fool disease is mentioned in the literature as early as 1583. The pathogen is the fungus "Taphrina pruni". However, this pathogen was discovered explicitly in 1860. Other variants of the genus "Taphrina" are, for example, the "Taphrina cerasi" (witches broom on cherry cultures) and "Taphrina deformans" (curling disease in peach cultures). Apricot, plum and bird cherry crops (Prunus padus), for example, are prone to pocket / jumbo disease. On the other hand, for example, mirabelle and Renekloden (a subspecies of the plum) are considered much more resistant. Especially a mild weather in the winter weeks in combination with increased moisture during flowering promotes a significant infestation with "Taphrina pruni".
Unique features of the infection
The clinical picture manifests itself in this way:
- The young fruits develop from May, compared to the fruit growth of healthy fruits, using a fungus-produced hormone (indolylacetic acid) much faster
- The result is curved, flat, pod-like fruits
- they show a length of about 4 to 6 centimeters and a thickness of about 1 to 2 centimeters
- The surface of these altered fruits is light green and smooth at the beginning and later on acquires a red touch, then becomes warty, wrinkled and appears yellowish / gray matt
- the pulp remains hard, green and succulent, the fruits are tasteless but non-toxic
- instead of the stone inside, there is an elongated cavity in its position
- If the spores are hurled out, they shrink and start to rot and fall prematurely
- the shoots and leaves of the cultures are attacked much less often
- This, however, shows miscarriage, curvature and thickening.
In principle, joint action is required especially for preventive measures within the neighborhood.
- If the infestation is rather weak, the affected fruits are picked as quickly as possible (before a Pflaumbildung) and thoroughly removed (bio bin). Under no circumstances should infected fruit remain behind.
- A regular cut of each tree as well as a precautionary protective coating with lime broth, in the period from October to November can reduce the infection pressure.
- Fruit crops in protected locations such as under a roof projection are largely spared infection because the moisture that promotes infection is usually not present here.
- Targeted spraying against the fungus "Taphrina pruni" at the time of flowering or at the time of budding and the start of shoot can be successful with plant strengthening agents as well as with fungicides.
Hibernation possibilities of the infection
The fungus "Taphrina pruni" survives virtually invisible 'saprophytic' (feeding on organic dead substances). In addition, various spores of the fungus are within the bud scales, so they are better protected from the cold than the fungus, which are located on the shoots. Thus, the fungus can infect the ovaries due to weather conditions at flowering. The surface of the affected fruit shows a mature coating during late spring. This bursts and thus provides the spores the material for hibernation.