How to control potato ring rot? Key points of control techniques in high-altitude cold regions

Potato ring rot is extremely widespread, occurring in almost all areas where potatoes are cultivated, and is especially severe in the Northeast region, where it can reduce potato yields by 20%-30%. It is a very serious bacterial disease that not only affects potato yield but also affects potato quality, with poor edibility, causing serious economic losses to agricultural production. Therefore, management should be strengthened and timely prevention should be carried out.

1 Distribution and harm

Potato ring rot occurs in Asia, Europe, North America, South America and other regions, and in China it is found throughout all provinces, cities and counties, being especially severe in the Northeast region, where it can cause phenomena such as missing plants, reduced yield and storage rot. In addition, due to the highly contagious nature of ring rot, producers have very strict requirements for seed potato quality. Once diseased plants are found in seed potato fields, they should be promptly removed to avoid transmitting the disease to other plants, and all infected potatoes cannot be used as seed potatoes.

2 Pathogen and epidemic

2.1 Morphology: Ring rot is caused by bacteria of the genus Corynebacterium, which is Gram-positive, does not produce spores, has no capsule, has no flagella, cannot move, and has cells 0.4-0.6 mm in size, mostly wedge-shaped, with some rod-shaped, curved or straight.

2.2 Temperature: The optimum growth temperature for this pathogen is 20-30°C, with a maximum of 31-33°C and a minimum of 1-2°C. The lethal temperature is 50°C, and after 10 min the ring rot pathogen dies.

2.3 Transmission by tools: It can be transmitted through cutting knives, containers and tools, so they must be disinfected before use. It can survive for a long time on containers and machinery. Cutting knives can be strictly disinfected with a 100-fold dilution of 40% formalin.

2.4 Cultivation conditions: The pathogen mainly overwinters in infected tubers. After harvest, these tubers are stored in cellars, and they can also overwinter in tubers left in the field and be transmitted to the next year through volunteer plants; it does not overwinter in the soil.

3 Symptoms

Ring rot is a bacterial disease of the vascular bundle. Infected aboveground parts show two types: leaf spot and wilting. The main one is the wilting type, in which wilting begins at the top compound leaves, the leaf margins curl slightly inward as if lacking water, and the disease spreads downward, with the leaves of the whole plant beginning to turn chlorotic, curl inward and droop, eventually causing the plant to lodge and die. When tubers are affected, cutting them open reveals that the vascular bundles turn yellow, then dark brown, and an arc-shaped necrotic ring forms in the cortex, hence the name ring rot. In severely infected tubers, the vascular bundles darken and rot appears.

4 Control measures

4.1 Select disease-resistant varieties. According to experimental surveys, varieties such as "Dongnong 303", "Netherlands Potato" and "Russian Potato" have relatively strong disease resistance and cold resistance, and should be selected according to local conditions.

4.2 Choose appropriate plots, because potatoes are cultivated to harvest more high-quality tubers, while tubers have weak soil-emergence ability and are prone to rotting from moisture, with severe ring rot. Therefore, choose sandy loam plots with high terrain, loose and fertile soil, deep soil layers, and easy drainage and irrigation.

4.3 Rational crop rotation. Rational crop rotation helps reduce diseases caused by the pathogen and lower the incidence rate. A rotation of more than 3-4 years can be carried out with cruciferous or grass family crops, and rotation with Solanaceae crops should be avoided to prevent worsening of the disease.

4.4 Strengthen field management, carry out timely hoeing and ridging, and eliminate field weeds. During the field growth period, potatoes are often attacked by diseases and pests. If not controlled in time, this seriously affects yield and tuber quality. Grasping the timing and carrying out early control is the main principle for controlling pests and diseases.

4.5 Harvest and store in cellars at the proper time. The north is relatively cold, so harvest promptly at the harvest period to prevent moisture-related tuber rot. The storage cellar should be dry, ventilated and at a suitable temperature.