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Judging by the photo, potato tubers are affected by glandular patches. This disease is also called rustiness of tubers.
Characteristics and causes of the onset of the disease
Glandular spotting is manifested in the form of brown (rusty) spots on the potato flesh. Coloring spots can vary and acquire different shades - from light amber to brown-red. The lesions are most often located around the circumference, closer to the core, but are scattered throughout the tuber. The spots have no clear shape, the edges are vague. Further rotting of the affected part of the pulp does not occur: it simply becomes solid, and starchy grains - are destroyed.
A characteristic feature of the disease is that it can not be detected by external examination - rustiness is visible only when the tuber is cut.
The causes of the appearance of the disease are a change in the composition of the soil and weather conditions, which lead to disturbances in the development of potatoes and their nutrition. These include:
- high air temperature;
- lack of moisture in the soil (drought);
- excessive amounts of iron and aluminum in the soil;
- lack of phosphorus.
Rusted tubers are not suitable for consumption, but they can be used for planting (the disease does not pass to the future crop).
Appears and develops rusty spotting only during the growth of potato bushes, during storage the disease is no longer distributed. Most often, rustiness affects planting in hot and dry weather, but it can also be with sufficient soil moisture in the event that the air temperature reaches 30 degrees Celsius. In a cold summer, when the temperature of the soil drops to 18-11 degrees, the disease does not manifest itself.
How to protect potatoes from rust?
First of all, for planting should be used zoned varieties that are resistant to this disease. In addition, it is necessary to ensure full nutrition of the tubers during growth. For this, periodically fertilize the soil with nitrogen fertilizers (organic, nitroammophoska), and also introduce phosphorus in the mobile form (superphosphate) during the entire developmental period. The liming of the site works well against rust.
Do not forget about the timely watering of plantings in arid days, as well as on lowering the soil temperature.
It is noticed that rusty spotting on potatoes appears less often if planted on a site on which lupine, lucerne, rape or olive radish first grew.