Early blight is the main disease of celery and can occur in both open and protected areas, resulting in severe reductions in production and quality.
Symptoms: Celery early blight, also known as leaf spot, spot disease. Early blight of celery mainly damages the leaves, but it can also harm the petioles and stems. The leaves were attacked and began to produce water-stained yellow-green spots, which later developed into round or irregular shapes, brown or gray-brown, yellow on the periphery, and lesion size of 4-10 mm. In severe cases, the lesions expand into patches and eventually cause the leaves to die. When the humidity is high, there is a gray and white mold layer on the lesion. After petioles and stems were damaged, the lesions were water-stained, showing oval spots or stripe spots, gray-brown, and slightly sunken. In severe cases, it can cause the petiole to fold down and even cause the whole plant to fall to death. When the humidity is high, there are gray and white moldy layers on the lesions.
Characteristics of the disease: The pathogen mainly grows with the diseased body in the field. When the conditions are appropriate, the overwintering diseased body produces conidia, which is transmitted through airflow, rainwater, and agricultural operations. It invades through celery stomata or directly penetrates the leaves and stem epidermis. Celery seeds can also be transmitted by bacteria. In addition, the early blight can continue to occur on the celery cultivated in the greenhouse, providing a source of bacteria for the onset of celery. Spores produced by open field celery can also infect studio celery.
The onset temperature is 25-30°C, high temperature and heavy rain or heavy dew condensation at night, and early blight is prevalent when the relative humidity is high. Lack of water, lack of fertilizer, poor growth of the plant when the disease is also heavy. The ventilation in the protected area is not timely, the stifling heat is high in the shed, the temperature difference between day and night is large, condensation is easy, and the onset is aggravated.
Control methods:
There is a difference in disease resistance or disease severity among varieties, and disease-resistant and mildly diseased varieties such as Jinnan Shiqin No. 1, U.S. Utah, Bresley celery, California King, and Ventura can be selected. Chemicals are used before sowing to kill or inhibit the surface of the seeds and germs lurking inside the seed coat. Can be soaked with 50% Formamide WP 600 times for 50 minutes, then rinse with clean water or dry to direct sowing.
At the early stage of disease, diseased leaves and leaves are removed in time. After the harvest, the diseased plant debris is removed, and the debris is deeply destroyed. The deep-buried land is combined with the land to reduce the source of infection. In serious diseased fields, the 1-2 year rotation can greatly reduce the number of disease sources. Protected cultivation should enhance ventilation and reduce humidity.
Spraying and spraying: 72% of frost urea Mn-Zn wettable powder 500-1000 times, or 30% of Ethericide water 1000 times, 50% of iprodione (promethine) wettable powder 800-1000 Doubling, or 58% methadone WP wettable powder 600-800 times every 7-10 days, continuous medication 2-3 times.
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