Bacterial wilt, also known as bacterial wilt disease, used to occur mainly in areas south of the Yangtze River basin. In the area north of the Yangtze River basin, due to climate and soil conditions, it did not occur or rarely occurred. However, with the rise of the sand industry in the northern regions, especially in the northwest region, rivers, slags, vermiculites, foam plastics and other substrates have been successfully used to carry out the cultivation of tomato in the solar greenhouse nutrient solution without using soil, making full use of wasteland, sand and desert areas, etc. Lands that are not suitable to be cultivated should give full play to the local light and heat resources, and the area for soilless cultivation of facilities should be expanded. Because the tomatoes in soilless cultivation systems are ecologically different from tomatoes in soil cultivation systems, they are closed systems with high temperature and humidity, and ventilation. In poor conditions, the low pH of the nutrient solution leads to a decrease in the pH of the substrate, which in turn makes the infestation of bacterial wilt worse. Often occurs in flowering fruit setting period, the ferocious, rapid development, serious disease incidence rate of 80% - 100%, the early fruit plants often have high mortality, facilities, soilless cultivation costs increase, economic benefits decreased significantly.
First, the law of occurrence
1. Symptoms: Bacterial wilt is a bacterial vascular bundle disease caused by Pseudomonas and begins to show symptoms after flowering in facilities without soil. Fall and winter pods of tomato are severe from December to February of the following year. In early spring, pods of tomato are severe between April and May, and the morbidity of pods is severe in autumn and November. In general, the top leaves wilted, then the lower leaves withered, and the middle leaves reacted at the latest. The diseased plants began to wilt only at noon, and they returned to normal when covered with straw and other coverings on the shed film in the early evening. If the greenhouse temperature is higher than 30°C, the diseased plants will no longer recover and die after the water shortage in the substrate for two to three days. Keep green, but lighter in color, so called bacterial wilt. If the greenhouse humidity is more than 85%, the irrigation or irrigation of nutrient solution is frequent, the roots of the diseased plants often turn brown and decay, the epidermis of the stems is rough and many adventitious roots of varying lengths can be produced, and the rhizomes become brown, and the stems are cut off and squeezed by hand. When pressure is applied, contaminated white mucus can be exuded from the color-changing catheter in the section, which is an important feature distinguishing with blight.
2. The relationship between high temperature and high humidity and onset: High temperature and high humidity conditions are suitable for the occurrence of bacterial wilt. In terms of temperature, the relationship between substrate temperature and incidence is relatively close. Generally, the substrate temperature is around 20°C, and there are fewer diseased plants. When the substrate temperature reached 25°C, the diseased plant rate increased significantly. In terms of humidity, substrate humidity and intra-facility humidity (RH) are the main factors affecting the disease. According to the survey, the substrate humidity and RH are around 60%, and the root rot rate is low. Above 80%, peak incidence occurs. Therefore, with the increase in irrigation volume and the shortened interval, the incidence becomes more serious.
3. The relationship between the pH value of the substrate and the onset: Generally, the soil in the northwest region is alkaline, but in the facility soilless cultivation system, the nutrient solution suitable for tomato growth has pH 5.5--6.5, and the matrix acidification is caused by the irrigation of the nutrient solution. It has created the conditions for the growth of pathogens and is a key factor in the pathogenesis. According to the survey, the substrate pH is 5.2--6.6, and the onset is serious. The onset of the disease is milder than pH 7.2. The matrix of calcium nitrate applied is lighter than that of ammonium nitrate. Therefore, the onset of acidic substrates is heavy, and the incidence of alkaline stromal cells is light.
4. Relationship between cultivation conditions and disease incidence: Pot cultivation is a common cultivation mode in facility cultivation techniques. The matrix in the tank is uneven, the irrigation and drainage system is not smooth, and water is accumulated in the planting hole and the tank. The incidence is serious. Reuse of the substrate caused the increase of bacterial wilt. Solanaceae vegetables are continuously cropped, and the disease is serious.
5. Transmission route: The pathogenic bacteria mainly in winter in the soil in the matrix and facilities along with the diseased body, and mostly invade from the root or the base of the stem. Therefore, in the facility, it mainly propagates through agricultural activities such as pruning, scaffolding, and topping, and irrigation or nutrient solution. In addition, pests such as underground pests and greenhouse insects in the facility are important media for transmission.
Second, control measures
1. Appropriate arrangements for cornices to avoid continuous cropping: the facility for soilless cultivation of tomatoes, can achieve annual production, the annual listing supply, it should be appropriate sowing, cultivation of disease-free strong seedlings, as far as possible in the flowering period to avoid high temperatures until the occurrence of bacterial wilt Most tomatoes have entered the harvest period, which can reduce the incidence of losses. Early spring pods, sowing in mid-December, planting in mid-February; autumn pods sowing in mid-July, planting in mid-August; wintering pods sowing in early October, planting in mid-November. At the same time, solanaceous vegetables on the same substrate should not be used for continuous cropping, and they should be rotated with legumes, melons, crucifers and other vegetables.
2. Seed disinfection: tomato seeds are generally dry-heat treated at 70-73°C for 3- 4 days, or treated at 53-55°C for 20-30 minutes, or with neutral hypochlorous acid at a concentration of 7000 mg/kg. Soak the calcium solution for 60 minutes, or soak the seeds in 10% trisodium phosphate solution for 15 to 20 minutes, remove and rinse with water, and sow after germination.
3. Substrate disinfection: The matrix reuse should be disinfected. Commonly used disinfection methods include steam and pharmacy. Steam sterilization is usually the pipeline into the substrate, covered canvas, and then pass 82 °C steam for about 30 minutes; disinfection can be used 40% formalin plus water 50 times at 20--40L / square meter dose applied to The substrate was covered with suffocation for 3 days, and then ventilated and dried for 2 weeks to completely volatilize the formaldehyde and ready for use.
4. Disinfection of nutrient solution: The water source used to prepare the nutrient solution should be clean and non-polluting. If surface water has to be used, sodium hypochlorite can be used for disinfection, but it is best to use tap water or non-polluted well water as the water source.
5. Facilities temperature and humidity management: during the seedling stage, maintain 22--25°C during the day and 15-18°C during the night. When transplanting the seedlings, they can be ventilated and cooled when exposed to high temperatures. The temperature can gradually change from 25°C to 18°C ​​to 12°C during the day and 12°C at night. It is conducive to nurturing strong seedlings. When the greenhouse humidity exceeds 70%, pay attention to ventilation and cooling. At the same time, according to different weather conditions as soon as possible to cover the late cover opaque, adjust the greenhouse light, is conducive to the control of temperature and humidity.
6. Nutrient solution management: In the tomato enters the result period, analyzes the nutrient composition regularly, adjusts the nutrient solution pH value at any time, makes the matrix pH value maintain about 7.2, is advantageous for the tomato growth not conducive to the growth of the bacterial wilt. The supply time of the nutrient solution was mainly during the day and was not supplied during the evening. Generally, the supply of the solution was once in the afternoon. The temperature of the nutrient solution directly affects the growth of the tomato. In summer, the liquid temperature in the high temperature condition often exceeds 30°C. The temperature should be maintained at about 25°C by using a reservoir in which the returning groundwater is laid in the storage tank or planting tank. The temperature of winter nutrient solution is lower than 12°C, and measures should be taken to maintain the temperature of the liquid pool at 15-16°C.
7. Elimination of pathogens and chemical control: Diseased plants found in the facility should be immediately removed and burned, and 2% formalin or 20% lime water should be used to disinfect the diseased hole, and lime powder can also be sprayed on the diseased points. In the initial stage of the disease, spray 200mg/kg of agricultural streptomycin, or use 500 times of 401 antibacterial agent to irrigate the root, 250--500ml of each irrigating solution, irrigation once every 10-15 days, successively 3 to 5 times.
First, the law of occurrence
1. Symptoms: Bacterial wilt is a bacterial vascular bundle disease caused by Pseudomonas and begins to show symptoms after flowering in facilities without soil. Fall and winter pods of tomato are severe from December to February of the following year. In early spring, pods of tomato are severe between April and May, and the morbidity of pods is severe in autumn and November. In general, the top leaves wilted, then the lower leaves withered, and the middle leaves reacted at the latest. The diseased plants began to wilt only at noon, and they returned to normal when covered with straw and other coverings on the shed film in the early evening. If the greenhouse temperature is higher than 30°C, the diseased plants will no longer recover and die after the water shortage in the substrate for two to three days. Keep green, but lighter in color, so called bacterial wilt. If the greenhouse humidity is more than 85%, the irrigation or irrigation of nutrient solution is frequent, the roots of the diseased plants often turn brown and decay, the epidermis of the stems is rough and many adventitious roots of varying lengths can be produced, and the rhizomes become brown, and the stems are cut off and squeezed by hand. When pressure is applied, contaminated white mucus can be exuded from the color-changing catheter in the section, which is an important feature distinguishing with blight.
2. The relationship between high temperature and high humidity and onset: High temperature and high humidity conditions are suitable for the occurrence of bacterial wilt. In terms of temperature, the relationship between substrate temperature and incidence is relatively close. Generally, the substrate temperature is around 20°C, and there are fewer diseased plants. When the substrate temperature reached 25°C, the diseased plant rate increased significantly. In terms of humidity, substrate humidity and intra-facility humidity (RH) are the main factors affecting the disease. According to the survey, the substrate humidity and RH are around 60%, and the root rot rate is low. Above 80%, peak incidence occurs. Therefore, with the increase in irrigation volume and the shortened interval, the incidence becomes more serious.
3. The relationship between the pH value of the substrate and the onset: Generally, the soil in the northwest region is alkaline, but in the facility soilless cultivation system, the nutrient solution suitable for tomato growth has pH 5.5--6.5, and the matrix acidification is caused by the irrigation of the nutrient solution. It has created the conditions for the growth of pathogens and is a key factor in the pathogenesis. According to the survey, the substrate pH is 5.2--6.6, and the onset is serious. The onset of the disease is milder than pH 7.2. The matrix of calcium nitrate applied is lighter than that of ammonium nitrate. Therefore, the onset of acidic substrates is heavy, and the incidence of alkaline stromal cells is light.
4. Relationship between cultivation conditions and disease incidence: Pot cultivation is a common cultivation mode in facility cultivation techniques. The matrix in the tank is uneven, the irrigation and drainage system is not smooth, and water is accumulated in the planting hole and the tank. The incidence is serious. Reuse of the substrate caused the increase of bacterial wilt. Solanaceae vegetables are continuously cropped, and the disease is serious.
5. Transmission route: The pathogenic bacteria mainly in winter in the soil in the matrix and facilities along with the diseased body, and mostly invade from the root or the base of the stem. Therefore, in the facility, it mainly propagates through agricultural activities such as pruning, scaffolding, and topping, and irrigation or nutrient solution. In addition, pests such as underground pests and greenhouse insects in the facility are important media for transmission.
Second, control measures
1. Appropriate arrangements for cornices to avoid continuous cropping: the facility for soilless cultivation of tomatoes, can achieve annual production, the annual listing supply, it should be appropriate sowing, cultivation of disease-free strong seedlings, as far as possible in the flowering period to avoid high temperatures until the occurrence of bacterial wilt Most tomatoes have entered the harvest period, which can reduce the incidence of losses. Early spring pods, sowing in mid-December, planting in mid-February; autumn pods sowing in mid-July, planting in mid-August; wintering pods sowing in early October, planting in mid-November. At the same time, solanaceous vegetables on the same substrate should not be used for continuous cropping, and they should be rotated with legumes, melons, crucifers and other vegetables.
2. Seed disinfection: tomato seeds are generally dry-heat treated at 70-73°C for 3- 4 days, or treated at 53-55°C for 20-30 minutes, or with neutral hypochlorous acid at a concentration of 7000 mg/kg. Soak the calcium solution for 60 minutes, or soak the seeds in 10% trisodium phosphate solution for 15 to 20 minutes, remove and rinse with water, and sow after germination.
3. Substrate disinfection: The matrix reuse should be disinfected. Commonly used disinfection methods include steam and pharmacy. Steam sterilization is usually the pipeline into the substrate, covered canvas, and then pass 82 °C steam for about 30 minutes; disinfection can be used 40% formalin plus water 50 times at 20--40L / square meter dose applied to The substrate was covered with suffocation for 3 days, and then ventilated and dried for 2 weeks to completely volatilize the formaldehyde and ready for use.
4. Disinfection of nutrient solution: The water source used to prepare the nutrient solution should be clean and non-polluting. If surface water has to be used, sodium hypochlorite can be used for disinfection, but it is best to use tap water or non-polluted well water as the water source.
5. Facilities temperature and humidity management: during the seedling stage, maintain 22--25°C during the day and 15-18°C during the night. When transplanting the seedlings, they can be ventilated and cooled when exposed to high temperatures. The temperature can gradually change from 25°C to 18°C ​​to 12°C during the day and 12°C at night. It is conducive to nurturing strong seedlings. When the greenhouse humidity exceeds 70%, pay attention to ventilation and cooling. At the same time, according to different weather conditions as soon as possible to cover the late cover opaque, adjust the greenhouse light, is conducive to the control of temperature and humidity.
6. Nutrient solution management: In the tomato enters the result period, analyzes the nutrient composition regularly, adjusts the nutrient solution pH value at any time, makes the matrix pH value maintain about 7.2, is advantageous for the tomato growth not conducive to the growth of the bacterial wilt. The supply time of the nutrient solution was mainly during the day and was not supplied during the evening. Generally, the supply of the solution was once in the afternoon. The temperature of the nutrient solution directly affects the growth of the tomato. In summer, the liquid temperature in the high temperature condition often exceeds 30°C. The temperature should be maintained at about 25°C by using a reservoir in which the returning groundwater is laid in the storage tank or planting tank. The temperature of winter nutrient solution is lower than 12°C, and measures should be taken to maintain the temperature of the liquid pool at 15-16°C.
7. Elimination of pathogens and chemical control: Diseased plants found in the facility should be immediately removed and burned, and 2% formalin or 20% lime water should be used to disinfect the diseased hole, and lime powder can also be sprayed on the diseased points. In the initial stage of the disease, spray 200mg/kg of agricultural streptomycin, or use 500 times of 401 antibacterial agent to irrigate the root, 250--500ml of each irrigating solution, irrigation once every 10-15 days, successively 3 to 5 times.
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