Symptoms

The infestation with Erwinia carotovora is a frequent cause for defects in the existence. Plants and/or single impulses in the existence vergilben, care and die finally. They can be pulled easily from the earth. The bacteria destroy primarily the cells of the supporting fabric of the To the finds one a typical black coloration with a strong fabric destruction of the so-called and stinging smell. The illness prevents the Wasserzufuhr upward and the evacuation of the Assimilate formed in the sheets into the tubers. The tuber wet rot transforms the tubers into a soft-putrid, breiige mass, which is held together only by the thin bowl and with light pressure bursts immediately. The typical stinging smell is however only released by secondary infections with certain other bacteria.

Biology of the harming exciter

The understanding of the biology of Erwinia is made more difficult by the fact that different subspecies of the bacterium occur, which can to settle and furthermore in their transmission way differ different in each case fabrics of the potato plant. Beside the potato Erwinia strikes carotovora also a number of other plants such as carrots, Kohl, Tomaten, Paprika, Zwiebel, Bohne, Erbse and

The most important source of the spreading is for both subspecies a latent (more visibly =nicht) infestation of the planting property, all planting tubers is latently infected. Particularly strongly the bowl and the Lentizellen (breathing openings) of the tubers are settled. The different planting property goods differ only in the extent of the settlement. The question about the transmission over the soil is not clarified until today finally. A substantial source of infection seems the soil only with very close succession of landlords (e.g. To be turned around carrots after potatoes or).

If the bacteria of the nut/mother tuber arrive directly at the impulse and grow the impulse up, they cause the typical symptoms of the Schwarzbeinigkeit there. The emergence of defects and/or of Schwarzbeinigkeit is favoured particularly by damp conditions after planting and during the youth development. Early planted existence, whose accumulate by cool, wet weather one retarded, are therefore affected by Schwarzbeinigkeit most strongly. Precipitation and low temperatures lead in the spring to intensified infestation.

On the tuber bowl responsible germs cannot arrive independently into the daughter tuber, therefore an infection of the tuber fabric is only directly over the nut/mother plant, or possible with the Bodenwasser over wounds and over the Lentizellen. A high soil water content creates favorable propagation possibilities and promotes a settlement of the Lentizellen, since these are opened with high humidity. Therefore heavy locations are more strongly concerned by tuber wet rot than easy. Injuries during the harvest and assortment work create entrance gates for the bacterium, a contact of the tubers with contaminated material (putrid-end tubers, dust, machine parts) during the harvest, dressing and storage increase the contamination degree of a tuber and/or a portion. Wet rot outbreaks, which are released by damages as consequence of mechanical injuries during the harvest and storage, are limited however to the initial phase of the camp period.

Whether after a successful settling of the tubers a rot actually breaks out, hangs off of the number of penetrated bacteria, the resistance reactions within the tuber as well as the conditions in the camp. Because with Erwinia the environmental condition (humidity and temperature) play a crucial role. Develops at temperatures above 10 "°C, the temperature optimum lies with 25-30 "°C. High humidity and small Sauerstoffkonzentrationen in the room air favour an outbreak, since by oxygen deficiency the resistance reactions of the potato are almost completely restrained. For the formation of a certain bacteria density is necessary (on the average 10,000 germs per gram). This is explained thereby that if bacteria occur over damages or over opened and unverkorkte Lentizellen the tuber fabric, these within the short time interval before a new cork layer forms, a sufficient quantity of enzymes to produce to have, which the destruction of the fabric advances, in order to win the race. For sufficient production at enzymes a certain quantity of bacteria is necessary, which overcome the resistance reactions of the tubers together. Under optimal conditions for the bacteria (no oxygen, damp) less than 100 bacteria per gram are enough, in order to cause a disease outbreak, while under aerobes conditions are necessary at the temperatures usual in the camp at least 1.000.000 to 10.000.000 bacteria cells per gram. Also a high nitrogen supply increases the danger of wet rot outbreaks, since after the Lentizellen later corks and offers to the bacteria during a longer period an entrance gate.

Fight and preventing measures

The fight of this bacteria illness begins with the use of as small as possible struck planting property. Precipitation and irrigation before accumulating the plants increase the danger of an infestation substantially. The harvest should take place only after reaching the bowl firmness with dry soil. The soil conditions to the harvest as well as the storage conditions in the first weeks after the storage are of paramount importance for the occurrence of For the avoidance of injuries the Rodearbeiten should take place at soil temperatures from over 10 "°C, the temperature in the soil should however no more than 20 "°C amount to.

A ten to fortnightly Wundheilungsphase as well as careful drying of the tubers after the harvest can contribute to the dismantling of the infestation pressure with Erwinia. An autumn assortment of the tubers - if it to go around actual should not be accomplished with care. It represents an additional substantial load.

A good ventilation during the entire duration of storage provides for an oxygen supply and prevents the formation of condensation and liquid films on the tuber surface as well as of anaerobic conditions in the stick.

Loose-shelled early potato portions represent a special problem also in the ecological agriculture, which are very injury-endangered. The lot shelledness causes that such portions sweat after the harvest at appropriate temperatures more strongly than festschalige potatoes in the autumn. For the avoidance of early potatoes should be gotten as coolly as possible from the soil, so that the bacterium in the tubers cannot develop so fast. This means that the Rodearbeiten should be usually locked early in the morning before 10 o'clock, because in the high summer the soil temperatures rise rapidly to 30 "°C and over it. Furthermore it should be prevented with the temporary storage in the camp and in the shop that a water film on the tubers develops. Potatoes also washed are particularly endangered. These portions should be dried after washing as fast as possible again. In the trade measuring instruments can be acquired, which measure the moisture content in the pile by determination of the electrical resistance.

Articles in category "Schwarzbeinigkeit"

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