How to control celery leaf spot caused by celery leaf spot disease

Celery leaf spot, also known as early blight. When the plant is damaged, the disease first occurs at the edge of the leaf and petiole, and gradually extends to the whole leaf, and the leaf is damaged, initially showing a watery yellow-green spot, and then round or irregular, the size of the spot is 2-15 mm, grayish brown, the edge color is slightly dark, the internal yellowing is thinner, not limited by the leaf vein, and in serious cases, the disease spot expands and converges into patches, resulting in celery leaves yellowing and dying. Celery stem or petiole is damaged, the disease spot is oval, the size of the disease spot is 3-23 mm, it begins to be yellow, slowly becomes grayish brown sunken, the stem is cracked, and in severe cases, the stem constricts, looms, and rotts at high humidity.

Celery leaf spot

Disease conditions: the optimum temperature for celery leaf spot is 22-30 ℃, and the relative humidity is 85%. The optimum temperature for conidia formation and germination was 15-25 ℃ and 28 ℃ respectively. It is easy to occur in high temperature, rainy and low-lying areas, but it is also easy to occur in the case of high temperature and drought condensation at night. In addition, the disease is serious due to lack of fertilizer, excessive irrigation or weak celery plants. 

Incidence regularity: celery leaf spot disease can occur in seedling stage and adult stage, and adult plants suffer more seriously, mainly harming stems and leaves. The next crop of celery leaf spot disease was mainly in Lanzhou, and the peak period was from July to September.

Integrated control technology: 

The main results are as follows: 1. Disease-resistant varieties are selected: Gaoyouta, California King, Ventura, Baili celery, crispy celery and other varieties have strong disease resistance.

2. Seed treatment: 

The main results are as follows: (1) soaking seeds in warm soup. Stir the seeds in 50 ℃ warm water to make the seeds heated evenly. Soak the seeds for 25 minutes and immediately put them into cold water to dissipate heat.

(2) soaking seeds with chemicals. Use chemicals to kill or inhibit germs on the surface of celery seeds and lurking inside the seed coat before sowing. Celery seeds can be soaked in 50% thiram wettable powder 600 times solution for 50 minutes, washed with clean water, dried, and sowed directly.

3. Clean the countryside: in the early stage of the disease, remove the diseased leaves and foot leaves in time; after harvest, remove the diseased remains of celery, concentrate on destroying deep burial, combined with deep ploughing of land to reduce the source of infection. The amount of disease source can be reduced by rotation for more than 2 years. 

4. The nursery (bed) of strong seedlings should be isolated from the place of production. Before raising seedlings. Thoroughly remove the celery remains and disinfect the soil. Choose cloudy days or evening to sow seeds, avoid high temperature, before sowing, first pour enough bottom water, and then fill the low-lying areas with fine soil to prevent uneven emergence or weak celery plants, cultivate disease-free and strong seedlings.

Celery leaf spot

5. Rational fertilization: the root system of celery is relatively shallow. After the previous harvest, apply 3000kg mature stable fertilizer per mu of celery, or sprinkle 1000kg mature human feces and urine, combined with deep ploughing, leveling and planting, so as to provide better conditions for celery plant growth and enhance celery disease resistance.

6. Field management: after celery planting slow seedling, fertilizer and water attack together to promote plant growth. Winter and spring production, large temperature difference between day and night, long time of condensation at night, easy to occur, we should pay attention to heat preservation and cold protection, reduce the temperature difference between day and night, prevent condensation, high temperature and rainy in summer and autumn, pay attention to drainage, irrigate with small water to prevent water accumulation in the border. In protected areas, ventilation should be strengthened and humidity should be reduced.

7. Spray prevention and treatment: at the initial stage of the disease, spray 50% thiophanate wettable powder 500 times, or 40% polysulfide suspension 800 times, or 77% carbendazim wettable powder 500 times, or 50% plus Ruinong wettable powder 400-500 times for 7-10 days, 2-3 times in a row. Under protected conditions, you can choose 5% chlorothalonil dust, 1 kg per mu of celery, once every 9 to 11 days. Or apply 45% chlorothalonil smoke remover, 200-250 grams per mu of celery, about 1 time every 9 days, continuous or alternating 2-3 times.