How to prevent and control ring rot in potatoes before sowing?

Potato ring rot is a common disease, but because the symptoms on the tuber, especially the external symptoms, are not obvious, it easily causes infection during seed cutting; and as the disease develops during storage, the tubers often rot in large quantities, resulting in abundant sources of inoculum. The following situations often occur in production: seed potatoes rot during sprouting; no seedlings emerge after sowing; seedlings die after emergence; diseased plants form, with few tubers set and small tubers, and seed potatoes rot away, causing serious gaps in the rows.

This disease is a bacterial disease, survives only a short time in the soil, mainly overwinters in the tubers, and can spread over long distances with diseased potatoes. It is a seed-borne disease, and as long as the seed potatoes are disease-free, no diseased plants will appear in the field. Therefore, pre-sowing control is crucial.

Control measures: for self-propagation, remove diseased potatoes while harvesting; after harvesting the tubers, first spread them in a ventilated place for 2~3 weeks so that the tubers enter the stage of dormant rest. Store them in the cellar when the temperature is stable at 0°C; before storing, strictly re-select the seed potatoes and remove diseased and rotten tubers, as well as tubers with mechanical damage, insect damage, flood damage, or cold damage. For storage, choose a wind-sheltered, sunny place with good drainage. During storage, ensure ventilation and air permeability,

Choose disease-resistant varieties suitable for local planting, such as Luyin No. 1, Zhengshu No. 4, Kexin No. 1, Wumeng 684, 697, 715, etc.

It is advocated to sow small whole tubers; sprout the whole tubers first and then cut them, and strictly disinfect the cutting knife. Small whole tubers have strong vitality and good disease resistance, and at the same time avoid cross-infection by ring rot bacteria and other pathogens, as well as poor healing of the cut surface and invasion by saprophytic bacteria. In production, it is advocated to give priority to using small whole tubers as seed potatoes. When cutting is necessary, it is advocated to sprout the whole tubers first and cut them just before sowing, so as to avoid long contact between cut surfaces. Before sprouting, strictly select and remove diseased potatoes. When cutting potatoes, each person should prepare as many cutting knives as possible; the knives should first be disinfected with alcohol or flame as necessary; observe the cut surface while cutting, and if the vascular bundles on the cut surface are found to have turned milky yellow to dark brown, first remove the diseased potato, then change the knife; before cutting, soak the knife in a 50 mg/L copper sulfate solution for more than 10 minutes.

Mix seed with plant ash: sprinkle a layer of plant ash on the cut surface, which not only keeps the cut surface dry and prevents pathogens but also adds potassium fertilizer, improving drought and cold resistance.

Apply chemicals in the holes: evenly sprinkle 50 g of 50 mg/kg copper sulfate poisoned soil into each hole.

Formulated fertilization and ridge cultivation: apply more organic fertilizer, with a nitrogen, phosphorus, potassium ratio of about 2.5:7:4.5; use superphosphate as the phosphorus fertilizer to supplement calcium; plant on ridges to enhance the disease resistance of the plants.