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Black potato scab is one of the main and most dangerous enemies of this root crop and gardener. It not only spoils the crop, reducing its quantity and quality, but also deprives it of the opportunity to procure home seed material. To defeat the potato rhizoctonia (as they call the disease), it is important to know what causes it and what conditions are favorable for development.
"Culprit" of rhizoctonia
The causative agent of black scab is parasitic and very viable fungus Rhizoctonia solani Kuehn. It is noteworthy that potatoes are not the only culture that he loves. The mushroom parasite is able to have other hosts, both among garden crops (solanaceous, pumpkin, cruciferous), and among weeds (special preference is for field horsetail and sow-stand).
Spores of fungus perfectly winter in the soil for 4 years, and in wet and cool weather begin to develop actively, while, the heavier and poorer the soil, the better they are feel. The mushroom parasite is also preserved on the tubers themselves, leading to damage to the crop during storage and subsequently infecting the shoots.
To eat the infected potatoes it is possible, but to use for reproduction - in no event.
How to understand that the potato is sick?
Black scab threatens potatoes at all stages of vegetation. Depending on when it happened, to determine that the culture is infected, you can by such signs:
- ripe vegetables are covered with black tubercles, sometimes merging into solid growths;
- when storing the crop spotted root crops start to rot;
- if the potatoes were able to winter, the sprouts that it produces in the spring are brown-red, strongly branching and very fragile;
- on the bushes afflicted with rhizoctonia, with the beginning of flowering there appears a white plaque beneath the stems and they rot;
- surviving bushes do not develop, remain low, leaves from the top begin to blush and curl;
- the sick young potato also stands out for ulcers, and gradually becomes rotten.
The fight against rhizoctonia is mainly in preventive measures aimed at preventing the creation of favorable conditions for the development of the fungus. To do this you need:
- Process the seed material before planting fungicides (Maxim, Bactofit and others).
- Every year, fertilize the soil with organic (especially manure) and mineral preparations.
- Observe the crop rotation in the garden beds.
- To start landing no earlier than the temperature will reach 8 degrees of heat and not "bury" the tubers too deep.
- To be in time to harvest before the onset of cool and damp autumn weather, which contributes to the development of the fungus (until September).
- All parts of the plant that are infected with rhizoctonia, including weeds, are burned.
If found in domestic potatoes tubers with black scab, it is better in the next season to completely change the inoculum, acquiring varieties resistant to this disease.