Control measures of Potato late Blight

Potato late blight, also known as blight, is a widespread and serious epidemic disease. When late blight was prevalent, the yield loss of non-resistant varieties could reach 20%~50%, the storage loss was 5%~10% and more than 30%. Late blight not only damages potato, but also tomato, pepper, eggplant and so on.

host plants

Potato, tomato, eggplant.

disease diagnosis

Leaves, petioles, stems and tubers can be damaged, and symptoms appear before and after flowering. Leaves infected, from the leaf tip or leaf edge began to produce water-soaked spots, humidity quickly expanded into brown spots, water-soaked edge, gave birth to a circle of white mold, leaf back mold layer is particularly obvious. Petiole and stem damaged, producing black-brown stripes, less white mold, often caused by wilting leaves, dry droop, late whole plant black wet rot. Potato block disease, brown spots to purple-brown, the disease part subcutaneous potato meat was also reddish brown. The lesion expanded into irregular patches, and the boundary between disease and health was often unclear. The disease part is not deep into the interior, often showing dryness and necrosis. The later period is easy to cause miscellaneous fungus infection and soft rot, has the strange smell, is unfit to eat. During cellar storage, the diseased part may continue to develop, resulting in a large number of rot.

The pathogen is Phytophthora infestans, whose hyphae are colorless, septless, multinucleated and slender. Cyst peduncle colorless, single root or fascicles from stomata, branched, upper uneven thickness nodular. Sporangia colorless, ovoid, with papilla-like projections at the top, water after the production of zoospores. The zoospores are kidney shaped and have two flagella on each side. The fungus can form resting chlamydospores in mycelium.

occurrence regularity

The pathogen overwinters mainly in the form of mycelium, which is the main source of disease infection. After sowing diseased tubers, serious ones could not germinate or die before budding, while light ones developed disease after emergence and became central diseased plants. Sporangia are produced in the diseased part. By air flow, rain transmission for re-infection, expansion and spread. Sporangia can also penetrate into soil with water to infect tubers, forming diseased tubers, which can be used as infection sources in the following year. The pathogen prefers warm days, cool nights and high humidity. Relative humidity above 95%, 18~22℃ conditions, conducive to sporangia formation. Rainy years, morning and evening foggy dew, wet weather, etc., conducive to the occurrence and spread of diseases. In northern potato planting areas, rainy seasons often occur before and after flowering. If the varieties are infected, the disease can spread in the whole field 10~14 days after the central diseased plant appears.

prevention measures

1. Application of disease-resistant varieties

All localities should select disease-resistant and high-yield varieties suitable for planting according to local characteristics.

2. Select disease-free seed potatoes

establish disease-free cultivation, selecting disease-free seed potato, harvesting in autumn, storing in winter, checking in cellar, discharging in spring, cutting before sowing, and strictly eliminating diseased potato in each step of vernalization process to avoid diseased potato falling to that ground and reduce primary infection source.

3. Strengthen cultivation management

Early sowing in due time, selecting loose soil and good drainage plots, rational fertilization, keeping plants healthy and enhancing resistance. If central diseased plants are found, they shall be removed and destroyed in time.

4. Timely chemical control

Spray immediately when you see a central diseased plant. 300 times solution of 40% Phosphoethyl aluminum wettable powder, or 600 times solution of 70% Mancozeb wettable powder, or 800 times solution of 25% Redoxycycline wettable powder, or 400 times solution of 64% Sandufan wettable powder, or 800 times solution of 72.2% Prochlor aqueous solution, or 600 times solution of 72% Kelu wettable powder, or 800 times solution of 47% Garinone wettable powder, or 1000 times solution of 69% Anke manganese zinc wettable powder can be selected.