Question 1: Symptoms, causes and prevention measures of nitrogen deficiency in cauliflower? A: Symptoms: The lower leaves are light brown with weak growth and development. Occurrence conditions: the soil itself has low nitrogen content; Before planting, a large amount of undecomposed crop straw or organic fertilizer is applied, which contains a lot of carbon, and nitrogen is taken away from the soil when decomposed. Prevention and control measures: fresh organic matter (crop straw or organic fertilizer) should be applied as base fertilizer, and nitrogen fertilizer should be added or completely decomposed compost should be applied; Emergency measures: spray 0.2% to 0.5% urea solution on the leaves. Question 2: Symptoms, causes and prevention measures of phosphorus deficiency in cauliflower? A: Symptoms: The back of the leaf is purple, because the pigment appears along the vein. Occurrence conditions: low compost and low phosphate fertilizer are easy to lack phosphorus; Ground temperature often affects the absorption of phosphorus. When the temperature is low, the absorption of phosphorus is less, and phosphorus deficiency is easy to occur in early spring; When the soil moisture is too much, it leads to low ground temperature and hinders the absorption of phosphorus. Prevention and control measures: when the soil is short of phosphorus, increase the application of phosphorus fertilizer; Apply enough organic fertilizers, such as compost. Phosphate fertilizer should be topdressing in time, and it can be applied 12.5- 17.5 kg of calcium superphosphate per mu, or sprayed on the leaves with 2%-4% calcium superphosphate aqueous solution, and sprayed 1 time every 7 days or so, 2-3 times. Question 3: Symptoms, causes and prevention measures of potassium deficiency in cauliflower? A: Symptoms: Irregular pale green or skin color spots appear between the veins of the lower leaves, and the connection loses green and gradually develops to the upper leaves. Occurrence conditions: low potassium content in soil, less application of organic fertilizer such as compost and potassium fertilizer, easy to lack potassium; Low ground temperature, insufficient sunshine, too wet soil and too much nitrogen fertilizer hinder the absorption of potassium. Prevention and control measures: apply sufficient potassium fertilizer; When symptoms of potassium deficiency appear, quick-acting fertilizers such as potassium sulfate should be applied immediately. Foliar spraying 1% ~ 2% potassium dihydrogen phosphate aqueous solution can also be carried out for 2 ~ 3 times. Question 4: Symptoms, causes and countermeasures of calcium deficiency in cauliflower? A: Symptoms: The tip is also stunted and deformed. The leaves near the tip have light brown spots, at the same time, the veins turn yellow and die from the upper leaves. Occurrence conditions: too much nitrogen, too much potassium or dry soil, which hinders the absorption of calcium; Air humidity is low, evaporation is fast, and calcium deficiency is easy to occur due to insufficient water supply; The soil itself lacks calcium. Prevention and control measures: soil calcium is insufficient, so calcium-containing fertilizer should be added; Avoid using a large amount of potash fertilizer and nitrogen fertilizer at one time; Water in time to ensure adequate moisture; Emergency measures: Spray the leaves with 0.3% calcium chloride aqueous solution. Question 5: Symptoms, causes and preventive measures of magnesium deficiency in cauliflower? A: Symptoms: The veins of the lower leaves are light green, and then bright yellow. Occurrence conditions: the soil itself contains low magnesium content; Excessive potassium and nitrogen fertilizer hinder the absorption of magnesium. Prevention and control measures: if the soil is diagnosed as magnesium deficiency, sufficient magnesium-containing fertilizer should be applied before cultivation; Avoid one-time application of excessive fertilizers such as potassium and nitrogen that hinder magnesium absorption; Emergency countermeasures: spray the leaves with 1% to 2% magnesium sulfate aqueous solution. Question 6: Symptoms, causes and countermeasures of boron deficiency in cauliflower? A: Symptoms: scattered water spots appear on the main stem and small flower stem, and the outside and inside of the flower ball turn black. Boron deficiency can occur at different mature stages of flower heads. When the lobules around the flower ball are short of boron, they are stunted or twisted. Broccoli lacks boron, and its stem is hollow. Occurrence conditions: soil drying affects boron absorption and is easy to lack boron; Boron deficiency is easy to occur in fields with low application of soil organic fertilizer and high soil pH value. Excessive application of potassium fertilizer affects boron absorption and is easy to lack boron. Countermeasures: the soil is short of boron, and boron fertilizer should be applied in advance; Water in time to prevent the soil from drying out; Apply more decomposed organic fertilizer to improve soil fertility; Emergency countermeasures: spray the leaves with 0. 12% to 0.25% borax or boric acid aqueous solution. Question 7: Symptoms, causes and countermeasures of zinc deficiency in cauliflower? A: Symptoms: poor growth, purplish red leaves or petioles. Occurrence conditions: zinc deficiency is easy to occur when the light is too strong; If too much phosphorus is absorbed, even if plants absorb zinc, they will show symptoms of zinc deficiency; Soil pH is high, even if there is enough zinc in the soil, it is insoluble and cannot be absorbed and utilized by crops. Prevention and control measures: don't apply excessive phosphate fertilizer; Zinc sulfate can be applied when zinc is deficient, and the dosage is per mu 1.5 kg; Emergency countermeasures: Spray the leaves with 0. 1% to 0.2% zinc sulfate aqueous solution. Question 8: Symptoms, causes and preventive measures of molybdenum deficiency in cauliflower? A: Symptoms: the leaves are long and narrow, the edges are curved and irregular, and the young veins are green, which is called "whiptail disease" and is not serious. Occurrence conditions: molybdenum is contrary to other trace elements, and its effectiveness to plants increases with the increase of soil PH value (that is, the alkalinity is enhanced). Therefore, generally speaking, the soil above 6.5 is seldom short of molybdenum, while the acidic soil and iron-rich soil are easy to be short of molybdenum. The soil available molybdenum was less than 0. 1 mg/kg, and the plants showed molybdenum deficiency. Prevention and control measures: improve soil to prevent soil acidification; Emergency countermeasures: spray 50 kg of 0.05% to 0. 1% ammonium molybdate aqueous solution per mu, and spray 1 to 2 times at seedling stage and flowering stage respectively. Question 9: Symptoms, causes and preventive measures of excessive boron in cauliflower? A: Symptoms: It turns white from the edge of the lower leaf. Occurrence conditions: firstly, it is necessary to know whether borax is applied to the previous crops or whether industrial sewage containing boron flows into the fields; The yellowing of cucumber leaves may be caused by high salt content or excessive potassium in soil, not simply by excessive boron. Artificial application of boron fertilizer makes the lower leaf edge yellow, and the symptoms further develop into yellowing and shedding in leaves, which may be the result of excessive boron. Prevention and control measures: The lower the soil pH value, the more obvious and serious the symptoms are. Applying calcium fertilizer can improve the pH value. Calcium carbonate is safer than calcium hydroxide in the process of crop growth; If there is excess boron, water can be poured, boron can be dissolved by water, and part of boron can be taken away by leaching; It is better to apply calcareous fertilizer after watering. Question 10: Symptoms, causes and countermeasures of excessive manganese in cauliflower? A: Symptoms: The upper leaves turn yellow and white, and the upper leaves appear yellow-brown spots. Occurrence conditions: soil acidification. Countermeasures: the solubility of manganese in soil increases with the decrease of pH value, so the application of calcareous fertilizer can increase the pH value of soil, thus reducing the solubility of manganese; In the process of soil disinfection, the solubility of manganese increases due to the action of high temperature and chemicals. To prevent excessive manganese, calcareous fertilizer should be applied before disinfection. Pay attention to field drainage to prevent soil from being too wet and soil solution from decreasing. 1. 1 downy mildew mostly occurs in the rosette stage, and yellow-brown polygonal or irregular spots appear on the lower leaves, and the edges are not obvious, which is limited by the veins. When wet, white mold will be produced on the back of leaves. Generally, it is serious when it is hot and rainy, the temperature difference between day and night is large, the sunshine is insufficient, the soil is stagnant, and the plant density is high.
1.2 brown spot mainly harms leaves, bulbs and seed pods. The lower old leaves come up first, and at the beginning, circular brown spots with concentric wheel patterns appear on the front or back of the leaves; When the humidity is high, a black mold layer will grow on the affected part. Generally, in the middle and late growth period, it is seriously ill in case of continuous rainy weather or insufficient fertility.
1.3 botrytis cinerea mainly harms inflorescences and stems and leaves. The diseased tissue is light brown, soaked in water, soft rot, and covered with gray mold. Bacteria spread through airflow, rain and agricultural operations, and invade the body from wounds or aging parts. It is easy to occur under the conditions of poor seedling growth, high density and high air relative humidity.
1.4 Sclerotinia sclerotiorum mostly occurs in the stage of heading, flowering and pod setting. The disease usually begins at the base of stem and petiole near the ground, and the lesion is brown at first and waterlogged. After the petiole was injured, the leaves withered and drooped due to water supply. In the case of high humidity, the diseased part is covered with white cotton-wool sclerotia. The disease spreads through soil and is easy to occur in warm and humid conditions.
1.5 Black rot damages leaves and bulbs. Adult plants usually develop from the lower leaves. Most lesions form V-shaped withered spots inward from the leaf edge, and the pathogen spreads downward along the vein, forming a large necrotic area or irregular yellowish brown spots, and the leaf tissue at the edge of the lesion is pale yellow. After the pathogen enters the vascular bundle of stem, it gradually spreads to bulb or vein and petiole, causing vascular bundle necrosis, blackening and finally death, but it is odorless. In dry conditions, the light bulb is black-hearted. In the field, germs are mainly spread by diseased plants, fertilizers, wind and rain or farm tools. The disease is easy to occur under the conditions of common seeds carrying bacteria, high temperature and rainy weather, improper management of fertilizer and water, continuous cropping with cruciferous crops and rampant pests.
The soft rot of 1.6 mostly occurs in the stage of ball bearing and pod bearing. Pathogens often invade from wounds, and initially water spots appear on the outer leaves or the base of bulbs; When the injury is serious, the whole plant rots, oozing purulent mucus, and the diseased part emits unpleasant smell. Bacteria spread through rain, irrigation water, fertilizers containing bacteria, insects, etc. Generally, seeds are infected with bacteria, with high temperature and humidity, too much watering, and many underground pests, which are prone to occur in continuous cropping.
1.7 virus disease can be harmful at seedling stage and adult stage. When infected at seedling stage, chlorosis and nearly round spots with a diameter of 2 ~ 3 mm are produced on the leaves, and then the color of the whole leaves becomes pale or mottled. When the adult plants are infected, except the young leaves are mottled, there are black necrotic spots on the back of the old leaves, and the diseased plants are scattered late. In production, there are many poisonous sources or aphids when sowing early, coupled with improper management, low terrain, no ventilation, or lack of water and fertilizer, the disease is serious.
2 Comprehensive prevention and control
2. 1 A slightly acidic soil with good drainage and loose fertility should be selected for rational land selection.
2.2 Seedbed soil disinfection nursery nutrient soil must be piled up for a long time and sealed with formalin for disinfection.
2.3 Disinfection of Seeds Soak the seeds in warm water at 50 ~ 55℃ for 20 minutes and keep stirring.
2.4 Crop rotation and non-cruciferous vegetable rotation can effectively reduce the occurrence of pests and diseases.
2.5 strengthen the management of seedlings, timely thinning and dividing seedlings, timely ventilation, reduce air humidity, and timely remove diseased seedlings.
2.6 Strengthening the management of water and fertilizer Broccoli likes water and fertilizer, and topdressing and watering in stages is the key to high yield. It is advocated to apply fully decomposed organic fertilizer as the main method, and compound fertilizer can be used as topdressing. In rainy season, ditch and drain in time to prevent soil water accumulation, so as not to cause root retting.
2.7 Improve the growth conditions and clean up the countryside in time; Remove diseased leaves and old leaves in time; Remove the residual plants and rotten leaves in the field in time after harvest; And do a good job of disinfection at the diseased point to reduce the source of bacteria. High border cultivation can effectively adjust soil temperature and humidity and improve lighting, ventilation and drainage conditions. Avoid damaging leaves and cutting roots during intertillage weeding, and destroy diseased plants in time to reduce transmission routes.
2.8 Pesticides can be used to control bacterial black rot and soft rot, and 5000 times of agricultural streptomycin or chloramphenicol can be used; To control fungal diseases such as downy mildew and Sclerotinia sclerotiorum, 500 times of 50% carbendazim or 600-800 times of 75% chlorothalonil can be sprayed every 7- 10 day for 2-3 times continuously, which can effectively control the occurrence of diseases. Spray pesticides regularly to kill aphids and other pests and cut off the route of transmission.