At what temperature is it appropriate to apply pesticides to flue-cured tobacco?

1. Environmental conditions for tobacco growth 1. Temperature: Tobacco is a temperature-loving crop. The above-ground parts can grow in the range of 8-38℃. The suitable temperature for growth and development is 25-28℃. , tobacco plants will die at minus 2-3°C. The underground part can grow between 7-43℃, but the most suitable temperature is 31℃. The optimal temperature for seed germination is 24-29℃, the minimum temperature is 7.5-10℃, and the maximum temperature is 35℃. When the temperature is lower than 7.5°C, the seed germination process stops; when the temperature is higher than 30°C, the germination process is slow; when the temperature exceeds 35°C, the germinated seeds will gradually lose their vitality. The tobacco transplanting period should generally be after the late frost and the temperature should not be lower than 10°C. The ideal daily average temperature during the leaf maturity period is about 24°C and lasts for 30 days to produce high-quality tobacco leaves. 2. Water: Generally, water is needed in the early stage of growth, most in the middle stage, and less in the later stage. It is advisable to keep the soil moisture at about 70% of the field water capacity during the seedbed stage. The water supply should be stopped 10-15 days before transplanting for seedling hardening. When transplanted to the seedling stage, the leaf transpiration is small, and the average daily water consumption is 3.5-6.4 mm. From seedlings to the clump stage, the average daily water consumption is 6.6-7.9 mm. It is appropriate to keep the soil moisture at 60% of the field water capacity. If it is less than 40%, the growth will be stunted. If it is more than 80%, the root growth will be poor, which is harmful to later growth. unfavorable. From the budding stage to the budding stage, the average daily water consumption is 7.1-8.5 mm, and it is advisable to keep the soil moisture at 80% of the field water capacity. If there is a lack of water during this period, the growth will be stunted. If there is a long-term drought, early flowering or early drying will occur. From budding to maturity, the average daily water consumption is 5.5-6.1 mm. It is advisable to keep the soil moisture at 60% of the field water capacity. The water should be slightly less during this period to improve the quality of tobacco leaves; if there is too much soil moisture, it will easily cause delays. Ripening and quality decline. 3. Sunshine: Tobacco always needs enough light, but most varieties do not have strict requirements on the length of sunshine. During the growth period, flue-cured tobacco requires sufficient but not very intense sunlight. The optimal lighting time is 8-10 hours a day. Especially in the mature period, sufficient sunlight is a necessary condition for producing high-quality tobacco leaves. Tantian, which is rich in short-wave light and warm, is conducive to improving the quality of tobacco leaves. 4. Soil: Although tobacco can grow on many types of soil, the soil requirements for growing high-quality tobacco are relatively strict. Red soil is the best, followed by red loess, sandy soil and mixed soil, while tidal loam soil (black soil) is the worst. 5. Weather phenomena: Strong winds and hail are more serious damage to tobacco leaves than to any other crops. Whether in the seedbed or field stage, they may cause serious losses. Therefore, tobacco cannot be grown in areas where strong winds and hail often occur during the tobacco growth period. 2. Tobacco cultivation and management 1. Select land for winter plowing: All plots where yellow tobacco is planted must be plowed in winter to a depth of 40-45 cm to eliminate some pathogenic bacteria and insect pests; the second is to increase the permeability of the soil; the third is to increase water holding capacity. Improve drought resistance, especially in areas with poor water resources. After the thaw in spring, rake the moisture carefully in time. 2. Soil preparation, fertilization, ridging and mulching. After preparing the land, rake the floor level again when making ridging. The humidity during making up the ridging should not be too high. The best relative humidity is 55%. According to the Gu dialect, the selenium melon pier is dry and the dust and smoke are raised. This means that if the humidity is high, it is easy to raise dust and smoke. It causes hardening and poor air permeability, which is detrimental to growth and development. The width of the ridge bottom is 75-85 cm, the height of the ridge is 25-30 cm, and the spacing between rows is 95-100 cm. The optimal ridge raising time is 15-20 days before transplanting. The bottom of the ridge has two lines of 5-8 cm, the ridge height is 25-30 cm, and the row spacing is 95-100 cm. The optimal time for ridging is 15-20 days before transplanting. Open two 5-8 cm furrows at the bottom of the ridge, apply half of the prepared base fertilizer into the furrow, raise the ridge to 15 cm, and then apply the other half in the middle, in the middle of the ridge top, and the width of the ridge top is 25-40 cm. It is in the shape of a trough with a concave center, which helps to preserve heat and moisture in the early stage. Before covering with wax, open a 5-8 cm trench from the middle of the ridge top and spray 2500 times 98% of Tianda's mould-repellent into the trench with two bags per acre. Then restore the flat ditch to its original state, use 100 grams of 50% acetochlor EC per mu, mix with 40 kilograms of water, spray evenly in the center of the ridge, then cover with film and wait for planting. It is best to use a 0.006-0.007 mm silver-gray aphid repellent film, which is good for preventing yellow leaf diseases. 3. Transplanting: Transplanting is the beginning of field cultivation and a key step in tobacco production. The benefit of this work is that it is related to the success or failure of the entire production period. The time must be when the daily average temperature is stable at 12-13 degrees Celsius. , should not be too early, nor should it be delayed. Too early will prevent frost damage, growth will be slow, and early death will occur easily, which will reduce the yield. Too late, the tobacco seedlings will be too large, the survival will be erratic, and the seedlings will be slow to return. Transplanting can be divided into dry planting. Regardless of the planting method, use 100 grams of ground mixed with 100 kilograms of fine soil, pinch it into the hole, and the plant will return to 50 centimeters, which is 1650-1950 dwarf. When sealing the soil, the height of the growth point of the tobacco seedlings 2 cm of topsoil is appropriate. 4. Preserve seedlings: After transplanting, hoe and check the seedlings within three days. If the seedlings are of poor quality or damaged by insect bites, add new seedlings in time and water them appropriately to ensure a 100% survival rate.

Comprehensive prevention and control: A. Two new leaves will grow in 6-7 days after transplanting. During the root-stretching stage, irrigate the roots with 2500 times of 98% Tianda Hypoxanil and spray 2116 on the leaves to strengthen the seedlings. 1500 times aphid sugram plus 500 times 20% virus A powder can effectively prevent and control damping off, root black rot, common mosaic virus diseases, tobacco caterpillars, aphids and other diseases and insect pests, ensuring healthy growth in the early stages. B. Ten-leaf stage: In this summer, the temperature rises, the precipitation is heavy, and the humidity in the soil is high, which is the peak period for the incidence of various diseases. Doing a good job in disease prevention during this period is the guarantee of a good harvest throughout the tobacco season. 2116 Tobacco-specific spray with 600 times the 1000 times the Tianda bacterium and 1500 times the Tianda 2% abamectin can effectively prevent and control the occurrence and damage of various diseases and insect pests. Spray again with 1000 times the 1000 times the bacterium virulence after an interval of 8 days. Kill, the effect is better. C. Fourteen-leaf stage: It is the peak period of the incidence of black shank and frogeye disease, and is also the secondary stage of common mosaic disease. 2116 Tobacco Special Type 600 times plus Tianda 98% Hypoxanil 2500 times, plus Virus A 20% powder 500x spray. D. Eighteen-leaf stage: It is the period of high incidence of brown spot disease and the peak period of aphids. Powdery mildew and thrips also occur at the same time. Spraying this medicine well is the last key. 2116 Tobacco special type 600 times plus DuPont fast net 2500 times plus days It kills aphids 1500 times faster, can effectively control the damage caused by diseases and insect pests, and ensure the normal growth and ripening of tobacco. 3. Field management of tobacco planting technology (1) Check and replenish seedlings, promote small ones and control large ones. After transplanting, it is necessary to water the seedlings and check and replenish the seedlings. When replanting, a small amount of compound fertilizer or quick-acting nitrogen fertilizer can be applied in the hole, and poison bait can be applied. Promote small seedlings and control large seedlings, so that the entire field grows uniformly to achieve complete, uniform and strong seedlings. (2) Cultivating and cultivating the soil: Generally cultivating 2 to 3 times, combined with weeding. For the first time, 7 to 10 days after planting, hoe lightly, do not turn over the soil, do not move the roots, and do not cover the seedlings. For the second time, 15 to 20 days after planting, the inside of the nest is slightly shallower, 6 to 7cm deep; the distance is slightly deeper, about 10cm, to remove weeds. The third cultivating should be carried out within 25 to 30 days after planting, combined with the last top dressing and soil cultivation. At this time, the root system is already well developed, and the cultivating should be shallow. If the tobacco plant shows strong growth potential without yellowing during the mature stage, it is necessary to stick it to one or both sides of the tobacco plant and cultivate it deeply and cut off part of the roots to promote yellowing and maturity. Soil cultivation can be carried out in combination with tillage and weeding. Only after the cultivation can the height of the ridge be 27-33cm, can it play the role of soil cultivation. If only one large soil cultivation is carried out, it should be carried out 25 to 30 days after planting. Too early or too late soiling will affect the growth of tobacco plants. (3) Water management 1. The water demand pattern of flue-cured tobacco The water demand pattern of flue-cured tobacco in the field period is generally less in the early stage, more in the middle stage, and less in the later stage. Less water is needed from transplanting to the ball, accounting for 4% to 10% of the total water requirement at this stage; the most water is consumed from the ball to budding, accounting for about 53%; after budding, it accounts for about 35%. The soil moisture in the seedling stage needs to be maintained at 65% to 70% of the maximum field water holding capacity; in the sapling stage, it should be maintained at 50% to 60%; in the long-term growth period, it should be maintained at 70% to 80%; and in the mature stage, 60% to 65% is appropriate. 2. Irrigation and drainage: The southern tobacco areas have abundant rainfall, but there are also droughts from time to time. If the surface soil dries to less than 60% of the maximum water holding capacity of the field, and the ground does not return to moisture in the morning, the leaves will wilt during the day and cannot recover in the evening, indicating the need for irrigation. Irrigation is best done in the evening or night. When transplanting, you need to water enough, usually 1.5 to 2kg of water per hole, and lhm2 requires 60 to 90m3 of water. Under dry and early conditions, watering can be done 1 to 2 times during the seedling stage, and each 1hm2 requires 150 to 300m3 water; during the root extension stage, as long as the soil moisture is not less than 50% of the maximum water holding capacity of the field, watering is generally not required; during the prosperous period, watering can be Water 2 to 3 times, each time 1hm2 requires about 7500m3 of water; when there is severe drought during the maturity period, it can be lightly watered 1 to 2 times, each time 1hm2 requires 300 to 450m3 of water. Hole irrigation (plant irrigation) or furrow irrigation should be avoided. Flood irrigation and flooding irrigation should be avoided. Tobacco is relatively drought-tolerant but not flood-resistant, and the fields cannot be flooded. (4) Topping and bud removal: To cultivate flue-cured tobacco for the purpose of harvesting leaves, measures must be taken to remove (wipe) the buds. Topping and removing buds can promote the growth of roots, stems and leaves, and is particularly effective in increasing the weight of leaves and improving the intrinsic quality of tobacco leaves. At present, the number of remaining flue-cured tobacco leaves is about 18 to 22. If it is still growing vigorously during topping, you can leave 1 to 2 more leaves; otherwise, you should leave 1 or 2 fewer leaves. According to the degree of inflorescence development, the topping period is divided into core topping and budding topping. Top with first flowers and top with blooming flowers. Generally, topping is mostly used during the budding stage and early flowering stage. Sbud topping consumes less nutrients and allows the top leaves to fully develop. The top leaves of the first flower topping have weak growth. The long-lasting smoke can be topped during the flowering period. Topping should be done on a sunny day, and the three small leaves under the inflorescence should be removed together with the flower buds. After topping, axillary buds will germinate from top to bottom and grow into tobacco branches, consuming a lot of nutrients and reducing yield and quality. Therefore, the buds must be completely removed to suppress the buds. Manually remove (wipe) the buds early, usually when the buds are 2 to 3 cm long. The buds are small, crisp and easy to apply, the wounds are small and easy to heal, and consume less nutrients, which is beneficial to the growth of leaves. Apply every 5 to 7 days. The use of tobacco sprout inhibitors can save labor and effort, increase quality and increase yield. In recent years, In-D (Primet250EC) produced by Heilongjiang Tobacco Company and Heilongjiang Petrochemical Institute and ACCOTAB330E produced by American Cyanamid Company have been used in my country, and both have good bud inhibition effects. The main methods of use are application and cup pouring.

(5) Preventing early flowering, bottom baking and cultivating fork tobacco l. Preventing early flowering. The phenomenon that tobacco plants bud and bloom without the number of leaves and height that should be expected according to the characteristics of the variety or perennial cultivation is called early flowering. The yield and quality of early-flowering tobacco plants decreased significantly. The vegetative growth of tobacco can be divided into basic vegetative growth phase and variable vegetative growth phase. The main factors that accelerate growth cones for flower bud differentiation during the variable vegetative growth phase are: low temperature. At 13~180C, last for 10~20 days. Low temperature. At 13-18℃, it lasts for 10-20 days. Seedling age. The older the seedlings are, the more sensitive they are to low temperatures and prone to early flowering. The length of sunshine. The temperature is below 20℃ and the sunshine is shorter than 8 hours. Drought or waterlogging or nitrogen deficiency. These are the causes of early flowering. To prevent early flowering, scientific tobacco planting must be carried out, and special attention should be paid to the temperature during the transplanting period. After early flowering occurs, cultivating tobacco can be used as an emergency remedy. 2. Prevent bottom baking. When tobacco leaves are not mature enough, the leaves near the ground will turn yellow or wither, which is called bottom baking. Bottom baking will seriously reduce product quality. Bottom baking is caused by poor environmental conditions that cause the normal metabolism of the tobacco plant to become disordered, and the growth of the lower leaves is damaged. Severe shading in the field and excessive humidity are called "water drying"; those caused by severe drought are called "drought drying"; in addition, nitrogen deficiency can also cause bottom drying. Bottom drying should be based on prevention, with reasonable dense planting, standardized cultivation, and improvement of the field environment. After bottom drying occurs, pick the drying leaves in time. 3. Cultivation of fork tobacco. When the nitrogen nutrition level of the tobacco plant is too high or early flowering occurs during the maturity period of the tobacco plant, using axillary buds to cultivate fork tobacco is a useful measure. The quality of branch tobacco is not as good as that of main stem tobacco, and is only used in special circumstances. There are top branches and bottom branches. Tobacco must be topdressed in time, topping at the right time, management should be strengthened, and quality should be improved. 4. Prevention and control of pests and diseases 1. Mosaic disease. First, pay attention to field operations and tool disinfection, promptly remove diseased plants and destroy them intensively. The second is to balance nutrition, improve nutritional resistance, reasonably mix nitrogen, phosphorus, and potassium fertilizers, and appropriately increase the amount of potassium fertilizer. Third, after the wheat harvest, efforts should be made to avoid and control aphids in a unified manner to cut off virus transmission routes. The fourth is to use 500-fold solution of Virus Bigram wettable powder, 400-600 times solution of Jinyebao wettable powder or 0.1% zinc sulfate and 20% virus A for prevention and control. 2. Angular spot and wildfire disease. First, the tobacco fields should be properly fertilized and irrigated to prevent excessive nitrogen fertilizer in the later period and increase the application of phosphorus and potassium fertilizer. The second is to promptly remove the diseased leaves when spotting occurs in the field, and spray 1:1:150 Bordeaux mixture or 2 million units of agricultural streptomycin or 50% DT500 times, spraying once every 7 to 10 days, continuously. More than 3 times. 3. Weather spot disease. The first is to strengthen field management, increase the amount of top dressing outside the roots, and improve the stress resistance of tobacco leaves; control the transplanting density, remove the bottom leaves in time, and enhance ventilation and light transmission. The second is to spray with 70% thiophanate methyl 500 to 1000 times solution, 50% zinc 600 times solution or 2 million units of agricultural streptomycin 500 times solution. 4. Tobacco caterpillar. The first is to adhere to the principle of "treat early and treat small" to eliminate pests before they are 3 years old (the gluttony period). The second is to kill larvae and eggs. Check the bottom leaves and leaf backs. If purple-brown eggs are found, spray them to kill them. Check the heart leaves and young leaves in time and kill them manually. The third is to kill 1,000 to 1,500 times with enemies. , 900% trichlorfon, 50% fenitrothion EC 1000 times, 50% phoxim EC 800 times, 90% Valin or Kuailing wettable powder 3000 to 5000 times, 50% Lefulin EC 1000 to 2500 times The results are ideal. Use pesticides alternately to prevent pests from becoming resistant to pesticides. At the same time, tobacco departments in various places should warn tobacco farmers that the prevention and control of tobacco pests and diseases must not only start early, but also prevent and control them scientifically. The occurrence trends of pests and diseases and problems in prevention and control must be reported or consulted in a timely manner to the tobacco department so that targeted measures can be taken. , Strictly prevent large-scale occurrence of pests and diseases.