In the process of cucumber cultivation in greenhouse, gray mold is a common and frequent disease. Once the gray mold is out, it will cause serious economic losses to the growers. Let's analyze the causes and prevention methods of gray mold. . First of all, we must understand the time of gray mold outbreak. The gray mold disease usually begins in the north shed in the end of October, and then enters the disease stage from north to south nationwide, gradually increasing in November; December and January, The deep winter season in February was the time of the outbreak; in June of the following year, with the increase of temperature, the gray mold of 80% of the country disappeared. Therefore, from the end of October to the second year of May, it is a critical period for the prevention and control of greenhouse cucumber mousse. 1 main symptoms Gray mold mainly infects cucumber melons and sometimes infects leaves. The typical symptoms on the melons are that they start to infect and rot from the residual flower and have a gray-black mold layer on them. The leaf damage begins to infect from the edge and presents an inverted "V" shape. To correctly understand gray mold, you can start from three aspects: brown spots; lesions appear inverted "V" shape; gray mold layer on the surface of the lesion, gray mold is gray mold is different from other diseases Obvious sign. 2 Causes of the disease 2.1 Low temperature Botrytis cinerea is a low-temperature and high-humidity disease. When the night temperature is too low, especially when the night temperature is lower than 15 °C, root growth is hindered and the absorption capacity is decreased. If it is lower than 12 °C for 3 consecutive days, the root hair will fall off, resulting in above-ground nutrition. Poor, yellowing of the edge of the leaves, etc., the symptoms of deficiency are obvious. The pathogen will start to infect from the leaf margin and cause disease. The young melons in this period will not only infect gray mold, but will also have a melon phenomenon. 2.2 Humidity in the shed is too large If the watering is too large or the watering method is unreasonable, the water in the greenhouse will increase the humidity in the shed, and the condensation time of the leaves or melons will be too long, which will create favorable conditions for the occurrence of gray mold. 2.3 Poor ventilation in the shed In the case of continuous rainy weather, especially in the deep winter season, the outside temperature is low, and some farmers are afraid of trouble not to expose the quilt, no ventilation, so that the seedlings grow in the air at a static, low temperature environment, the plant resistance is reduced, and the pathogens are invaded. dye. In addition, if the planting density is too large and the field is closed, it will cause poor ventilation and poor light transmission, which will reduce the resistance of the seedlings. 2.4 wounds Artificially causing wounds, such as pruning, playing old leaves, arranging flowers, picking melons, spraying drugs and other agricultural operations as well as insect bites, phytotoxics, and fertilizers, can cause wounds and create opportunities for pathogen invasion. 2.5 seedlings grow prolonged, lack of potassium, calcium deficiency, leaf senescence The more probiotic seedlings appear, the worse the disease resistance; the formation of calcium pectate between the potassium-deficient and calcium-deficient seedling cells is insufficient, the cells are not tightly connected, and the disease resistance is reduced; in addition, the more prolonged seedlings The more prone to premature aging, the excessive consumption of nutrients, the consequent decline in resistance, and the infestation of pathogens. 2.6 Other diseases infested If other diseases such as downy mildew have infested the seedlings, the gray mold pathogen will also take the opportunity to carry out secondary infection, causing gray mold to occur. 2.7 There are residual flowers After the fruit is set, the tomatoes can be removed, but the cucumbers are different. When they are sold, they must be topped with flowers. The cucumber consumers who do not have flowers do not like it, but the flowers of cucumber are the most important infection path of gray mold. Pay attention to the protection of the flower. In short, high humidity, low temperature, wounds, residual flowers, and old and weak diseased leaves are prone to gray mold. Because the bacteria is Pythium, it has no initial infection ability and can only be infected twice. If the plant has no wounds and no premature death, it will not be infected with gray mold. 3 pathogenic bacteria Botrytis is a fungal disease caused by Botrytis cinerea. It is spread by means of airflow, rain, dew, and farming operations such as pruning, snoring, and flowering. 4 preventive measures 4.1 Increase the temperature of the greenhouse and increase the light transmission Try to increase the temperature of the greenhouse, especially in the deep winter season. Due to the short lighting time and the long night time, the temperature of the greenhouse must be 32 °C during the day to store heat in the greenhouse to ensure that the minimum night temperature reaches 15 °C. Under the temperature conditions, the seedlings can survive the long cold night and are protected from Botrytis cinerea. Then, using a PO film with good light transmittance or other dripping and fog-reducing greenhouse film, the better the shed film, the lower the probability of occurrence of gray mold. The shed film should be cleaned and enhanced in light transmission. It can be cleaned with the dust strip and cleaned with the wind. It is very convenient. 4.2 Reduce the humidity in the shed The shed can be controlled by drip irrigation or micro-spraying, which can effectively control the watering amount. High ridge cultivation can not only effectively improve the ground temperature, but also reduce the humidity around the root system. In addition, the planting line is covered with plastic film, and the straw is laid in the operation line. Sawdust can not only effectively reduce the humidity in the shed, but also control the amount of evaporation in the field. 4.3 Increase ventilation as much as possible In the deep winter season, or encounter continuous rain, snow and smog weather, insist on uncovering the ventilation and ventilation of the shed to avoid the environment in which the seedlings are in the dark for a long time and the air is not circulating, causing the seedlings to grow long and make the leaves thick and thin. Elongation, excessive consumption of nutrients, leading to premature aging of plants, decreased disease resistance, creating conditions for the invasion of pathogens. 4.4 Protecting flowers In order to prevent the infection of the germ from the flower, a medicament for preventing gray mold may be added to the scented medicament. Tests have shown that the best protective effect on the flower is 25 g / L fluke nitrile suspension seed coating agent (Shilo), followed by 50% flavonoid wettable powder (Huiyou) 200 times solution, after use Proper ventilation. 4.5 Supplementing potassium fertilizer and calcium fertilizer, delaying leaf senescence During the growth period, the supply of potash and calcium fertilizer should be ensured, especially after the melon is planted, and measures should be taken to delay the senescence of the leaves, such as spraying sugar, calcium fertilizer and amino acids on the foliar surface. Once every 15 days, the leaves can delay the aging. day. It should be noted that in the deep winter season, do not apply potassium nitrate, because low temperature will cause the seedlings to selectively absorb nitrogen fertilizer, thereby reducing the absorption of potassium and calcium fertilizer. 4.6 Remove sick bodies, including diseased leaves, old leaves, diseased flowers and diseased fruits After the diseased plants, diseased leaves and diseased fruits are found, they are covered with plastic bags and removed to the outside of the shed for centralized treatment. And knock out old leaves, yellow leaves, etc., to reduce the path of pathogen transmission. 4.7 Using air disinfectant The gray mold pathogen spreads with the airflow, and the spores of the pathogen float in the air, where there is water and where it falls, and then infect; if it is waterless, it will always float in the air, and the disease will not occur. Therefore, the occurrence characteristics of the gray mold pathogen can be fully utilized, and the air disinfectant can be used to kill the spoiled spores. Specific method: After closing the shed at night, use 30 pieces of air disinfection tablets per 667 m2, divide into 5 points, use 6 pieces per point, you can use a disposable plastic cup, pour 50-100 mL of water, water temperature 20 ~ 30 °C (In this range, the higher the temperature, the better the effect). It is placed on the wire on the top of the plant or about 1 m on the back wall to play the role of air disinfection. The continuous rainy and hazy weather is better. 4.8 Strengthen management Avoid artificial wounds, necrotic tissue, etc. in the seedlings, and create no chance to infect the bacteria. In the management process, we always put the control work in the first place, try to delay the aging of the leaves, improve the toughness of the plants and leaves, and enhance the resistance. Especially before the onset of continuous rainy weather, it is necessary to spray organic nutrients such as control agents and leaves to supplement sugar, so as to avoid the lack of nutrient supply due to the length of the plants, resulting in decreased resistance. When using foliar fertilizer or pesticides, it is necessary to master the concentration and application time to avoid the occurrence of fertilizer or phytotoxicity, damage the leaves, and provide opportunities for pathogen infection. When it is rainy, evening and when the temperature is lower than 16 °C, do not pruning the old leaves, otherwise it is not conducive to wound healing, and the bacteria will take the opportunity to invade from the wound. 5 treatment methods The principle of prevention and control of gray mold is to remove the sick body in time, improve the temperature, strengthen the ventilation, and use the drug-assisted sterilization to achieve the purpose of treatment. The method is as follows. 1 After the discovery of gray mold, immediately disinfect the seedlings with disinfectant. Spray with 50% chlorobromoisocyanuric acid soluble powder 1500 times. The dosage should be large, and the spray effect must be achieved. thoughtful. 2 On the 2nd day after the disinfectant is used, it must be followed up with a systemic strong agent. It can be used with an active ingredient content of 400 g/L pyrimethanil suspension 1 000 times or an active ingredient content of 50% boscalyl ( Kaiser) water dispersible granules 1 200 times liquid spray. Under normal ventilation conditions, the disease will be effectively controlled on the third day. 3 If you can't ventilate in the rain and snow weather, you can spray it again on the third day, and use it alternately with the medicine used on the second day. The gray mold of cucumber in the greenhouse must be paid attention to, and timely prevention and control measures should be taken to prevent cucumber from being invaded by gray mold. Different methods of prevention and control in different regions, the above content is for reference only. If you want to know more about agricultural technology, please pay attention to the Hui Nong School!
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Causes and prevention methods of frequent occurrence of cucumber gray mold in greenhouse