How to use medicine for carrot black spot disease

(1) symptoms. Stems, leaves and petioles can all be infected. Leaf infection mostly starts from the tip or edge of the leaf, showing irregular dark brown to black spots, the surrounding tissue aggravates discoloration, black mildew layer grows on the spots with high humidity, serious spots converge, the leaf margin rolls up, and the leaves wither early. The stem is infected, and the disease spot is oblong, dark brown and slightly sunken. (2) the condition of onset. The disease is a fungal disease. The pathogen overwinters on seeds or diseased bodies with hyphae or conidia. Spread and re-infect by airflow. In general, the disease is serious in the fields with weak plant growth in the rainy season. (3) Prevention and treatment methods. ① pulled out the diseased plant in time and buried it deeply. ② should be watered in time when the weather is dry to prevent the soil from drying and wetting, and proper application of phosphorus and potassium fertilizer can make the plant grow healthily and increase its disease resistance. ③ collected seeds from disease-free plants and collected them only. ④ has carried out crop rotation for more than 2 years. Before sowing ⑤, seed was mixed with 50% thiram wettable powder, or 40% seed dressing powder, or 70% mancozeb, or 75% chlorothalonil, or 50% promethoin wettable powder. The dosage of the reagent is 0.3% of the seed weight. In the early stage of ⑥, 75% chlorothalonil wettable powder was sprayed, or 58% metachlorothalonil manganese zinc wettable powder 400 times, or 40% carbendan wettable powder 300 times 400 times, or 50% propofol wettable powder 1500 times, once every 10 days or so, for 3 times.