Seeds are one of the most important ways to spread vegetable pathogens. With the sowing of diseased seeds, on the one hand, the new epidemic area can be continuously expanded. In particular, once the quarantine diseases are introduced, the future troubles are endless; on the other hand, they can be aggravated. The damage caused by the original disease caused greater losses. The germs that the seeds carry can directly infect the seed buds and seedlings, resulting in the destruction of seedlings, and provide pathogenic sources for later onset, which is the root cause of the disease in the field of vegetables.
1 Vegetable Seed Strains and Parts
1.1 The species of the pathogenic fungi that cause the transmission of bacterial pathogenic fungi by fax are generally propagated in different parts of the seed by vegetative or propagating organisms, but are also spread among seeds for transmission.
1.1.1 The pathogens are mixed in the seeds. Diseases that are mixed with pathogens or inclusions between the seeds spread diseases, such as the sclerotia of Sclerotinia sclerotiorum, often mixed in cabbage seeds, along with cabbage seeds sowed into the soil. Under appropriate conditions of temperature and humidity, the sclerotia will germinate the ascitium plate and emit ascospores to infect.
1.1.2 The attachment of pathogens to the seed surface generally means that the fungal asexual spores or sexual spores adhere to the surface of the seed to spread the disease. Some germs adhere to the surface of host seeds with conidia, such as cucumber anthracnose and tomato leaf mold; some bacteria attach to the seed surface with oospores, such as pepper blight, welsh downy mildew, etc.; in addition, some Germs can also adhere to the outside of seeds with conidiospores or sclerotia to spread disease.
1.1.3 Pathogens Latent in the seed coat The pathogens are usually lurking in the seed coat in the form of mycelium and the disease is transmitted. Such as cucumber wilt, cabbage black spot and so on.
1.1.4 Pathogens Latent in seed coat tissue or pathogens in seed embryos are usually latent in the form of mycelia within the seed coat or within the seed embryo to spread disease. For example, chilli brown spot, eggplant verticillium wilt lurk in the form of mycelia within the seed coat, and the mycelium of the blastocyst and endosperm of the pepper embryo and endosperm has blight.
1.2 Species-borne bacterial pathogens The phytopathogenic bacteria do not have dormant organs like fungi, and they often adhere directly to the seed surface or lurk inside the seeds. After the vegetable seeds are infected by the pathogenic bacteria, on the one hand, the seeds can be rotted. For example, the cabbage is attacked by black rot pathogens, and the seeds are often completely rotted, or the embryos are infected, and the buds and cotyledons become black rot; on the other hand, Seed discoloration, beans infected by bacterial pathogenic bacteria, the formation of red-brown, slightly depressed lesions in the pupa.
1.2.1 Pathogens The pathogenic bacteria that adhere to the surface of the seed, such as the bacterial blight of pepper, adhere to the appearance of the seeds. In dry conditions, they remain dormant for a long period of time. When the seeds germinate, the cotyledons are infected and form lesions. The bacteria spilled from the cotyledon lesions and invaded other parts of the plant.
1.2.2 Pathogens The pathogenic bacteria that lurk in the seeds of this type of seed disease are lurking within the seed coat or within the seeds. Bacteria such as the bean bacterial blight are latent in the seed coat, while bacteria of the cucumber bacterial leaf spot are lurking in the seed coat, endosperm and embryo.
1.3 Species-borne viral diseases are different from species-borne bacterial pathogens and species-borne bacterial diseases. Seed-infected viruses are caused by the combination of specific viruses and plants. For example, the seeds of cowpea can transmit the mosaic virus transmitted by cowpea, while the cucumber mosaic virus does not spread through the seeds of cucumber, but it spreads through the seeds of wild cucumber and melon. This should pay special attention to the seed treatment.
1.3.1 External transmission of virus from seeds This type of virus contaminates the appearance of seeds. Virus diseases of tomatoes, watermelons, melons and other crops are mainly caused by the seeds contaminated with pulp.
1.3.2 Internal transmission of virus in seeds can be divided into two types: external propagation of virus in embryos and internal transmission of viruses in embryos. In general, virus transmission is the second type. The virus is present in the embryo of the seed. When the seed germinates, the virus is transmitted from the interior of the embryo to the seedling.
2 Vegetable Seed Processing Methods According to the different kinds and locations of vegetable seeds and different types of vegetables, different seed treatment methods can be adopted, which can be broadly divided into physical and chemical methods.
2.1 Physical Methods for Seed Processing
2.1.1 Seed selection is the use of specific gravity to eliminate pathogens or diseased seeds between seeds. The selection includes hand selection, water selection, screening and mechanical selection. Based on differences in size, specific gravity, morphology, or roughness of pathogens or diseased seeds and healthy seeds, pathogens such as sclerotia, bacillary dysentery, and diseased seeds that are intermixed in seeds are removed. For example, Sclerotia sclerotiorum sclerotia mixed in the seeds can be removed with clear water, saline, 20% (specific gravity 1.478) or 30%-40% yellow muddy water. In general, diseased seeds cannot be sufficiently mature or even mature, and they are lighter than healthy seeds. Therefore, diseased species can be removed by means of air separation.
2.1.2 Thermal treatment is the method of using heat resistance of seeds and pathogens to kill pathogenic bacteria. The most common method is warm soup soaking and dry heat treatment.
1 Soaking with warm soup: It is an effective way to use a certain water temperature to eliminate germs inside and outside the seed. Since some pathogenic bacteria are lurking inside the seeds and are difficult to be treated with general agents, they can be killed by soaking seeds with warm soup. The method is to soak the seeds for some time in warm water of a certain temperature, then remove the seeds, put them in cold water and cool them, and then dry them; if some seeds need to be germinated and sowed, they do not need to be dried and can be sowed directly after cooling. The time and temperature of soaking depends on the heat-resistance of the vegetable seeds and the limit of lethal temperature of the pathogen. In principle, the soaking time should be shortened when the water temperature is high, and long when the temperature is low. It is safer to use this method if there is a large difference in the degree of heat resistance between vegetable seeds and pathogens. On the contrary, it should be avoided.
2 dry heat treatment: refers to the seeds in the dry hot air, dry heat sterilization at a certain temperature for a certain period of time, in order to achieve the purpose of killing the seeds inside and outside the bacteria.
2.2 Chemical treatment of seed treatment refers to the treatment of seeds with various chemicals before or during seed processing. Through chemical treatment of seeds, on the one hand, pathogens attached to the outside of the seed and germs latent inside the seeds can be killed or inhibited; on the other hand, the seeds and young buds can be protected from infestation by pathogens in the soil. The commonly used chemical methods are seed dressing, soaking and boring.
2.2.1 Seed dressing method 1 Dry seed dressing method: Mix the dried powder with the dried seeds before sowing so that each seed adheres evenly to the powder and forms a medicine coat. Because the medicine used for seed dressing is powder, it is difficult to penetrate directly into the interior of the dry seed, so the killing effect on the bacteria latent inside the seed is poor. Dry seed dressing is best operated with a seed coater. If there is no seed dressing and the number of seeds is small, a jar or jar can be used for seed dressing. 2 Wet seed dressing method: Wet the powder with a very small amount of water and then pick it, or mix the dried powder on the wet seed. This is a new phenomenon that emerged after the widespread use of the systemic fungicide. Seed dressing method.
2.2.2 Seed soaking method is to impregnate the seed with the chemical solution, so that it absorbs the liquid, after a certain period of time out to dry and sowing. Most soaking agents need to be washed clean with water after soaking, and then air-sowing or direct germination. Soaking must strictly control the liquid concentration, soaking time, liquid temperature, etc., otherwise it will affect the efficacy or phytotoxicity. The advantage of the soaking method is that the operation is relatively simple, no special equipment is required, and the physical properties of the chemical agent are not very high. With this method, seeds can be infiltrated into the seed, so the ability to kill germs inside the seed is better than seed dressing.
2.2.3 The boring method is to spray the seed with a relatively small amount and a relatively high concentration of liquid medicine, mix evenly, heap up smoked stuffy stuff and cover it with plastic cloth, etc., and it will be turned during the boring process for a certain time. This kind of treatment is suitable for volatile agents and has the effect of gas smoke. The boring method has the advantages of both soaking and seed dressing. However, this method requires more liquid. The treated seeds have absorbed a lot of water. If they are not sown for a long time, they will generate heat, which will greatly reduce the seed germination rate. Therefore, it should be Seed sowing after 2d (days).
3 Main Vegetable Seed Carrier Strains and Seed Treatment Methods According to different parts and types of vegetable seeds, proper seed treatment methods should be adopted. According to the nature of pesticides, the two types of fungicides that can be used in combination can be soaked in mixed formulations, but the concentration of each agent should be halved. In general, soaking in warm soup is suitable for preventing and controlling most of the species of fax fungus diseases. If you need to use this method for seed dressing, it must be dried after the seeds are dried, otherwise it will produce phytotoxicity. Seeds that have been treated with a chemical seed dressing are usually used directly for sowing instead of germination. If the treated seeds are germinated, they should be soaked with chemicals. Wet seeds can not be directly seeded with pesticides, but must first be air-dried and then seeded. The following describes the treatment methods of several vegetable seed carriers. When it is specifically applied, an appropriate treatment method should be adopted for a major disease.
3.1.1 Control cucumber anthracnose, blight 50 Â°C warm soup soaking 20min (minutes); acetic acid 100 times or formalin 200 times soaking 30min (minutes); 50% thiram soakable 500 times liquid soaking 20 minutes (minutes).
3.1.2 Control cucumber black spot, root rot, scab, blight wilt 55 Â°C soaking 15min (minutes); 50% carbendazim WP 800 times +50% acetaminophen 800 times soaking 60min (minutes ); Seed dressing with 0.3% seed weight of 50% carbendazim WP.
3.1.3 Prevention of cucumber disease 72.2% Preclosure 800 times solution or 25% metalaxyl WP 800 times soaking for 30 minutes (minutes).
3.1.4 Prevention of cucumber bacterial leaf spot, leaf blight 30 days (minutes) of calcium hypochlorite 300 times soaking; 40% formalin 200 times soaking 60 minutes (minutes); 1 million units of streptomycin sulfate 500 The solution was soaked for 2 h (hours); the dry seeds were dry-heat treated at 70Â°C for 72 h (hours).
3.2.1 Prevention and treatment of tomato early blight, spot blight, black spot 52 Â°C warm soaking 30min (minutes); 50% acetaminophen wettable powder 500 times soaking 50min (minutes).
3.2.2 Prevention of tomato leaf blight, wilt disease 52 Â°C warm soup soaking 30min (minutes); 2% Wuyimycin agent 100 times liquid soaking 60min (minutes); copper sulfate 1000 times soaking 5min (minutes); with seed amount 0.4% of 50% Ketandan wettable powder dressing.
3.2.3 Prevention of tomato canker and bacterial scab The dried seeds were dry-heat treated at 70Â°C for 96 hours (hours); 55Â°C warm soup soaked for 25 minutes (minutes); 1 million units of chloramphenicol 1000 times soaked for 2 hours (hours); Potassium manganate 1000 times liquid soaking 20min (minutes).
3.3.1 Prevention of pepper anthracnose, white spot, brown spot 55 Â°C Wen Tang soaking 30min (minutes); 50% carbendazim WP 800 times +50% thiram soakable 800 times liquid Soak 800min (minutes).
3.3.2 Control pepper broth 52 Â°C warm soup soaking 30min (minutes); copper sulfate 1000 times soaking 5min (minutes); 72.2% Precike water 800 times or 25% metalaxyl WP 800 times soaking 60min ( Minute).
3.3.3 Prevention of pepper bacterial sore disease 52 Â°C Wen Tang soaking 30min (minutes); clear water immersion 12h (hours) after soaking with copper sulfate 500 times 5min (minutes); 1000000 units of 500 times streptomycin sulfate soaking 30min ( Minute).
3.4 eggplant verticillium control of verticillium wilt, brown streaky, wilt disease, can be soaked in warm soup 49 Â°C 20min (points); with seed weight 0.3% of 50% thiram seed wettable powder seed dressing; with seed weight of 0.2% of 50% grams Dandan wettable powder dressing; 50% carbendazim wettable powder 500 times liquid soaking 60min (minutes).
3.5 Cruciferous vegetables
3.5.1 Prevention and treatment of cruciferous vegetables black rot, clubroot disease soaked at 50Â°C for 20 minutes (minutes); 45% Daisen ammonium hydroxide solution soaked for 20 minutes (minutes); 1 million units of streptomycin sulfate 500 times Seed soaking for 2 hours (hours); use seed weight 0.4% 50% citric acid copper copper wettable powder dressing.
3.5.2 Prevention and treatment of cruciferous vegetables with white typhoid, black spot 50 Â°C warm soup soaking for 20 minutes (minutes); seed weight 0.3% of 50% thiram WP or 50% acetaminophen wettable powder dressing.
3.6.1 50% carbendazim wettable powder seed dressing of bean anthracnose, wilt disease seed weight 0.4%; 40% formalin 300 times liquid soaking seed 20min (minutes).
3.6.2 Soybean Bacterial Disease Soaking at 45Â°C for 15 minutes (minutes); 1 million units of streptomycin sulfate 1000 times for soaking 12 hours (hours); seed dressing with 95% enemy seed weight of 0.3%.
3.7 spinach prevention and control of downy mildew with 25% metalaxyl WP 800 times liquid soaking 60min (minutes).
3.8 Welsh onion prevents purple onion spot and downy mildew with 40% formaldehyde 400 times soaking for 2 hours (hours); 50% acetaminophen WP 1000 times + 25% metalaxyl WP 1000 times soaking for 50 minutes (minutes); Soak in 25 minutes at 50Â°C.
3.9 celery control celery leaf spot, spot blight with a temperature of 50 Â°C warm soaking 25min (minutes); 50% thiram soaking 50cm (minutes).
3.10 Controlling soft rot of pods soaked with streptomycin sulphate 500ppm for 1 hour (hours).
3.11 ginger ginger scab disease soaking with streptomycin sulfate or neomycin 500mg.kg-1 48h (hours); 40% formalin 150 times soaking 6h (hours); 30% copper oxychloride 800 times liquid Soaking for 6h (hours).
3.12 The control of sputum sputum disease with 50% carbendazim WP 800 times stuffy species 24h (hours).
3.13 Control of stem blight with a 50% thiophanate-methyl wettable powder 800 times liquid dip bulbs 24h (hours).
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