Tomato gray mold is one of the most important diseases of tomato cultivation in greenhouses. It is like low temperature and high humidity. The indoor and outdoor climate in winter and spring is very suitable for its development. In recent years, the disease has been increasing year by year in our county.
First, the incidence of disease and disease characteristics
1. The law of incidence
The disease is caused by the infection of the genus Botrytis. At a temperature of 20 to 30°C and a relative humidity of 90% or more, it is a suitable condition for the occurrence of the disease. Protected areas are generally susceptible to disease from February to June. The pathogens are spread by airflow, irrigation water, and agricultural operations. Spiked flowers are the main human route of transmission. Germs are invaded by dead tissues such as wounds and aging organs. The flowering period is the peak period of infection.
2. The characteristics of the disease
2.1 Botrytis cinerea is characterized by strong rot and widespread host
The disease can infect tomatoes, peppers, cucumbers, beans, strawberries, lettuce, leeks, zucchini and other vegetables. Widespread disease, strong pathogen vitality. According to reports, the bacteria can still survive for more than 10 days under the condition of a temperature of 50°C. The conidia have strong drought resistance, and they still have viability in 138 days under natural conditions.
2.2 early onset, long period of occurrence
From December to May of the following year, it was the epidemic period of gray mold. From February to March, it was the peak period of onset.
2.3 Rapid spread of the epidemic
It usually takes only 7 to 12 days for gray mold to go from onset to epidemic. The pathogen spreads from the defeated flowers, wounds, and necrotic tissues through gas flow, rain, and agricultural operations. Farming operations such as pruning, inserting racks, going to old leaves, toppings, and flowering can all be artificially transmitted.
2.4 prevention and control
Botrytis cinerea is a kind of pathogenic bacteria that can easily produce drug resistance. The conventional pesticides include benzimidazoles (bencendazole, thiophanate-methyl, etc.), trichloromethylthiols (captans, sterilized dans, enemy bacteria). Dan et al.) The control effect of fungicides on grey mold was extremely unstable.
2.5 loss of weight
Botrytis cinerea damages the flowers, leaves, stems and fruits of tomatoes, especially the victims of green fruits. The flowering period is the peak period of pathogenic infection, and the rapid increase of tomato yield with the use of fast vine fertilizer during the fruit enlargement period is the peak period of onset. The remaining stigma or petals are mostly infested and spread to the stalk or fruit surface. The fruit is damaged, the diseased part becomes soft, and finally rots, resulting in a direct loss of yield.
Second, the main causes of the outbreak of Botrytis cinerea
1. Suitable for climatic conditions
The humidity in the shed is high, and the relative humidity in the air can reach 80% during the day and 90% at night. In the greenhouse, more than 75% of high humidity in the shed can induce the epidemic of gray mold.
2. Irrational use of drugs
Many vegetable farmers are unfamiliar with the onset symptoms, disease characteristics, and control agents and use techniques of tomato gray mold. Metalaxyl, B-aluminum, anti-virus, mancozeb, and streptomycin are not used as pesticides. The disease is very poor.
3. When medication is not suitable for prevention and treatment
Botrytis cinerea is a disease induced under low temperature and high humidity conditions. Once it is onset, it will become an outbreak in the short term. Many farmers cannot use the medicine in time and miss the best time for prevention and control.
4. Do not use medication
There are three kinds of methods for the prevention of gray mold in tomato: spraying, smog method and dust method. In case of continuous rainy (snow) weather, the smog method and dust method should be used for prevention and control. Spraying method should not be used.
Third, prevention and control technology
1. Focus on soil and shed body disinfection to control source bacteria
1.1 When plowing, mu is applied to 50% carbendazim 1.5 kg, or 1 kg of 50% dexamethasone to kill the pathogenic bacteria in the soil.
1.2 15 to 20 days before planting, the shed film is fastened, and the greenhouse is closed for 15 to 20 days. The shed is sterilized so that the temperature in the shed can reach 50 to 60°C and the maximum temperature can reach 70°C. This can kill the pathogenic bacteria in the shed and reduce the burden. The occurrence of disease.
1.3 During the high-temperature period in the July-August month of the Hughada period, the deep-water irrigation of sheds is maintained for 20 to 25 days, and high-temperature “cooking of fields†can kill soil pathogens.
2. Improve cultivation techniques and improve ecological control
2.1 Strengthen the control of temperature and humidity, change temperature management. After clearing the straw curtain in the morning, the air was released for 30 minutes to reduce the relative humidity in the shed to 70% or less, and then the shed was closed to increase the temperature of the shed to 32 to 35°C. High temperatures above 31oC are detrimental to the development of germs, and photosynthesis of tomatoes is beneficial. The ventilation was continued at noon and in the afternoon so that the temperature in the shed was maintained at 23 to 28°C and the relative humidity was controlled below 75%. When the temperature in the booth drops to 18-20°C, the vents are closed, the night temperature is maintained at 14 to 16°C, and the relative humidity is maintained at 70 to 80%. Cloudy weather also requires ventilation to remove moisture.
2.2 to promote the full coverage of dark film irrigation technology. When watering, the water goes under the membrane, trying to slow irrigation with small water, and not flooding. Watering is best done on a sunny day, avoiding cloudy or afternoon watering. Immediately after watering, close the vents, so that the temperature of the shed rises to 33~35°C for 1 hour, then quickly release the air to remove moisture. After 3~4 hours, if the temperature of the shed falls to 25°C, the shed can be heated to 33°C. , Continue for 1 hour, then release the air, reduce the relative humidity in the shed as much as possible, and reduce the incidence of disease.
2.3 Combine farming operations such as pruning and topping, remove old leaves, yellow leaves and diseased leaves, diseased branches, and diseased fruits in a timely manner, bring them out of the shed to be deeply buried or burned, and reduce the number of pathogenic bacteria that are re-infected and infected.
2.4 After the tomato harvest, the straw, dead branches, and defoliant debris are promptly removed from the shed for centralized stacking, and they must not be thrown into the fields or trenches.
2.5 Local conditions should be selected as far as possible to select suitable local varieties of high-yield, gray mold resistant. At the same time, promote the use of high-light energy drip-free agricultural film, scientific fertilization, cultivating strong seedlings and other cultivation measures to effectively prevent the occurrence of gray mold.
3. The correct use of chemical pesticides to improve the control effect
3.1According to the characteristics and laws of the incidence of Botrytis cinerea, seize the three key periods of medication: 1 spray a “pedestrian†before planting, and use a 50% Suo Keling wettable powder on the tomato seedbed for a protective spray 1500 times , to prevent sclerotinia germination spore infestation; 2 during flowering, with the first fruit, when the flowering, in the well-prepared tomato spirit or 2,4-day dilution plus 0.1% of 50% fast-king After the WP is fully mixed, the pods are sprayed; 3 The medication is applied on the day before and at the onset of the rinsing of fruit water (especially when the first and second ear fruit is watered) to form a protective film on the surface of the fruit. Inhibit the infection of fruits by Botrytis cinerea. Can choose 50% Suo Keling wet powder 1500 times solution, or greenhouse tomato winter spring alfalfa cultivation technology 65% ​​anti-milkweed wet powder 1500 times, or 65% triamcinolone wet powder 800 times, or 50 % of polymyxin WP 1000 times, or 28% of fungal wet powder 1500 times, or 65% of Wan Ling WP 1000 times, or 25% of pyrimidine WP 800 times. Spraying should be done on a sunny morning, 7~10 days once, and spray 2~3 times.
3.2 Improve spray technology, mainly including: 1 Spraying should be comprehensive. Not only must the plants be carefully and thoroughly sprayed, but also the greenhouse film, floor, and shed space must be sprayed to achieve complete sterilization. 2 Spraying should grasp three key points. First, the greenhouse should be sprayed with high humidity before it develops. It is important to spray. Second, the back and middle leaves of the plants should be sprayed on the back of the leaves. Third, the plants around the central disease should focus on spraying. . 3 Each spraying should be alternately used or mixed with fungicides to control botrytis to avoid cross-resistance in single use.
3.3 Reasonable choice of application methods. Greenhouse tomato Botrytis cinerea agent control methods include spray method, smog method and dust method. In rainy (snow) weather, spraying methods should not be used, and smog method and dust method should be selected.
3.3.1 Smog method: Close the greenhouse, use 10% fast Ke Ling smoke agent or 45% chlorothalonil smoke agent, 250 grams per mu, in the evening with dark fire closed smoked overnight, the next day to open the door ventilation.
3.3.2 Dust method: It is possible to use 10% extinguishing powder dust agent, or 5% chlorothalonil dust agent, or 10% killing spirit dust agent, or 10% gray mold spirit dust agent, and 1 kilogram of an acre dosage per acre. Spray in the evening.
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