At present, the disease has become an important disease of celery in winter and spring protected areas, and has a great influence on the yield and quality.
Symptoms? The main damage to the leaves, but also damage the petiole and stem. Leaf lesions have two types of small spots and large spots. In the early stage, they were light brown oil-like spots, and gradually enlarged to the central brown necrotic spots. The diameter of the small spot is usually less than 3 mm. The shape of the spot is nearly circular to indeterminate. The outer edge is yellow-brown, and the central part is yellow-white to gray-white. Some spots have yellow halo around the spot. Large spots can be expanded to 7 to 10 mm with dark brown edges and brown middle parts. Both spots showed scattered small black spots (conidia). Petiole, stem lesions nearly diamond-shaped to oblong, slightly concave, brown, pale interior, scattered small black spots.
Pathogen? The pathogen Septoria?apiicola Speg. called celery culm, and S.apii Chest said that the celery shell spores and S. apii-graveolentis Dorogin called celery large shell spores, are all fungi of the subphylum Fungi. The conidiospore was buried in the epidermis and its size was 87--155 and 4*25--56 microns. It escaped from the orifice of the device and escaped from the spores and conidia. Spores are colorless, transparent and long-lined. The top is relatively blunt, with 0--7 septa, more often than 3, and 35-55*2--3 microns in size. When the conidia germinate, the diaphragm increases or breaks into several sections, and each section can produce germ tubes. Mycelium and conidia lethal temperature 48--49C. After 30 minutes. The conidial germination temperature ranged from 9 to 28C. The bacteria grew well under high temperature, and the optimum temperature for development was 20-27C. It was higher than 27C. The growth and development slowed down. It only infringes on celery.
The characteristics of the disease? Mycelia and mycelia with the remnants of the disease left over in the soil to survive the winter, or mycelium in the seed strain and seed coat latent overwintering. The endogenous conidiospores of the spores were used as primary invasive and re-invasive inoculums. They emerged from the orifices of the spores of the spores and spread through rain spattering. They penetrated through the stomata or epidermis and invaded into the bacteria. ~ 27 °C, and requires high humidity, the presence of water droplets when the spores are more likely to release and germination. The cold weather is generally cold and humid and rainy weather is most conducive to disease. Protected cultivation, such as poor ventilation, high humidity, easy to induce low moisture, low fertility, poor fertilization, growth of weak fields and plants are more severe. There are differences in resistance between varieties. Foreign cited Italian winter celery and summer celery, beautiful cited Florida 683 (but high temperature and drought susceptible black heart disease), Utah 10-B, Emerson pas-cal, June Bell and early Green, Tianjin's Jinnan Ciqin, Shanghai's Daqin, and Beijing's 8401 (bred from Shanghai Daqin) all showed resistance to spot blight, which can be selected according to local conditions.
Control methods
1, choose resistant varieties. Such as Jinnan celery, winter celery, Xiaqin, Jinqin, Tianma, Shanghai Daqin, Ventura, American glass crisp, Celery 3, Chunfeng and so on. Use disease-free seeds or sterilize diseased seeds. From the disease-free strains or seedlings stored for 2 years. Strengthen field management, apply basic fertilizers, see seedlings and enhance plant resistance to disease.
2, open field can be sprayed with 75% chlorothalonil WP 600 times, 40% Fuxing (fluorosiliconazole) 8000 times, or 45% Tecto suspension 1000 times, or 50% acetaminophen can be wet Powder 1,000 times. 5% of chlorothalonil or 6.5% of moldoyl dust or 45% of chlorothalonil aerosol can be used as protection ground, and it can be controlled for two to three times every 7-10 days.
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