The latest control measures of potato late blight

Potato late blight, also known as blight, is a common and serious epidemic disease. All potato planting areas have occurred, non-resistant varieties in the epidemic of late blight, field yield loss of up to 20%-50%, light cellar loss of 5%-10%, heavy more than 30%. Late blight not only harms potatoes, but also harms tomatoes, peppers, eggplant and so on.

Host crop

Potatoes, tomatoes, eggplant.

Disease diagnosis

Leaves, petioles, stems and potato pieces can be damaged, and most of them show symptoms before and after flowering. When the leaf is infected, water-immersed spots begin to appear from the leaf tip or leaf edge, and quickly expand into brown spots when the humidity is high, and the edge is flooded, resulting in a circle of white mildew, especially in the mildew layer on the back of the leaf. Petiole and stem damage, resulting in black-brown stripes, less white mold, often causing leaf wilting, dry and sagging, and black wet rot of the whole plant in the later stage. Potato block disease, the spot brown to purple-brown, the diseased part of the subcutaneous potato meat is also reddish brown. The disease spot expands into irregular patches, and the boundary between disease and health is often unclear. Most of the disease departments do not go deep into the interior, often showing dry and hard, necrotic. In the later stage, it is easy to cause miscellaneous bacteria infection and soft rot, which has a strange smell and can not be eaten. During the cellar storage, the disease department can continue to develop, causing a lot of decay.

The pathogen is Phytophthora infestans, whose hyphae are colorless, septate, multinucleated and slender. The cyst pedicel is colorless, single or bundled from the stomata, branched, and nodular in upper part. The sporangium is colorless, ovoid, with papillary protuberances at the tip and produces zoospores after water absorption. Zoospores are visceral, with two flagella on the side. The pathogen can form dormant chlamydospores in the hyphae.

Morbidity regularity

The pathogen overwintered mainly in the form of mycelium, which became the main source of disease infection. After sowing diseased potato, the heavy ones could not germinate or the buds were not unearthed and died, while the light ones became sick after being unearthed and became the central diseased plant. Sporangia are produced in the disease. Through the airflow, Rain Water spread to carry out re-infection, expansion and spread. Sporangia can also infect potato tubers with water infiltration into the soil to form diseased potatoes, which can be used as the source of infection in the following year. Germs prefer warm days and cool nights and high humidity. The relative humidity is more than 95% and the condition of 18-22 ℃ is favorable for sporangium formation. Rainy years, foggy and dewy in the morning and evening, humid weather, etc., are conducive to the occurrence and spread of diseases. In the northern potato planting area, there is often a cloudy and rainy season before and after flowering. If the variety is susceptible, warm and humid, the disease can spread throughout the field 10-14 days after the occurrence of the central diseased plant.

Prevention and cure measures

1. Application of disease-resistant varieties

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

2. Select disease-free seed potato

Establish disease-free seed field, select disease-free seed potato, achieve income cellar in autumn, store cellar in winter, get out of cellar in spring, cut pieces before sowing, and strictly eliminate diseased potato in every step in the process of vernalization to avoid diseased potato and reduce the source of primary infection.

3. Strengthen cultivation and management.

Sowing early at the right time, selecting the land with loose soil and good drainage, applying fertilizer reasonably to keep the plant strong and enhance the resistance. The diseased plant in the center was found and removed and destroyed in time.

4. Timely chemical control

Spray immediately if there is a central diseased plant. You can choose 40% ethanophosphate-aluminum wettable powder 300x liquid, or 70% mancozeb wettable powder 600x liquid, or 25% Ruidui wettable powder 800x liquid, or 64% poisonous alum wettable powder 400x liquid, or 72.2% Pulicol water agent 800x liquid, or 72% Kelou wettable powder 600x liquid, or 47% Carrinone wettable powder 800x liquid, or 69% Anke Manganese Zinc wettable powder 1000 times liquid.