At what temperature is pesticide suitable for flue-cured tobacco?

1. Environmental conditions for tobacco growth. Temperature: Tobacco is a thermophilic crop and can grow in the temperature range of 8-38℃ on the ground. The optimum temperature for growth and development is 25-28℃. When the temperature is lower than-2-3℃, the tobacco plant will die. The underground part can grow at 7-43℃, but the most suitable temperature is 3 1℃. The optimum temperature for seed germination is 24-29℃, the lowest temperature is 7.5- 10℃, and the highest temperature is 35℃. When the temperature is lower than 7.5℃, the seed germination process stops; Above 30℃, the germination process is slow; If the temperature exceeds 35℃, the germinated seeds will gradually lose their vitality. Generally, the transplanting period of tobacco should be after late frost, and the temperature should not be lower than 65438 00℃. The ideal daily average temperature of leaf maturity is about 24℃ for 30 days, which can produce high-quality tobacco leaves. 2. Moisture: 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 in the seedbed stage, and stop water supply and hardening seedlings 10- 15 days before transplanting. Transplanted to seedling stage, the transpiration of leaves is small, and the average daily water consumption is 3.5-6.4 mm. From seedling returning to tree gathering stage, the average daily water consumption is 6. 6-7。 9 mm, the soil moisture should be kept at 60% of the field capacity; Below 40%, the growth will be hindered, while above 80%, the root system will grow poorly, which is not good for the later growth. The average daily water consumption from clumping stage to budding stage is 7. 1-8.5 mm, and it is appropriate to keep the soil moisture at 80% of the field capacity. At this stage, if there is water shortage, the growth will be hindered, and if there is a long-term drought, there will be early flowering or early drying. From budding stage to mature stage, the average daily water consumption is 5.5-6. 1 mm, and the soil moisture should be kept at 60% of the field capacity, and the moisture should be slightly less at this stage to improve the quality of tobacco leaves. If there is too much soil moisture, it is easy to delay maturity and reduce quality. 3. Sunshine: Tobacco always needs sufficient sunshine, but most varieties are not strict about the length of sunshine. Flue-cured tobacco needs sufficient sunshine in the growth period, but it is not very strong. The daily illumination time is 8- 10 hour, especially in the mature period. Adequate sunshine is a necessary condition for producing high-quality tobacco leaves. Sunny days with short wave components are beneficial to improve the quality of tobacco leaves. 4. Soil: Although tobacco can grow on various types of soil, the requirements for planting high-quality tobacco are very strict. Red soil is the best, followed by red loess, sandy soil and mixed soil, and moist loess (black soil) is the worst. 5. Weather phenomenon: gale and hail weather do more harm to tobacco leaves than any other crops, which may bring serious losses in seedbeds or fields. Therefore, tobacco cannot be planted in areas where strong winds and hail often occur during the tobacco growing period. Second, tobacco cultivation management 1, winter ploughing: all plots planted with yellow tobacco must be ploughed in winter with a depth of 40-45 cm to eliminate some pathogenic bacteria and pests; The second is to increase the permeability of soil; The third is to increase water conservation capacity and improve drought resistance, especially for plots with poor water sources. After thawing in the next spring, grab the soil in time and rake it flat. 2. Soil preparation, fertilization, ridging and film mulching. When ridging, the prepared plots should be leveled and raked again. When ridging, the humidity should not be too high, and the relative humidity is 55%. In the valley, the dry selenium melon mound and dust smoke mean that if the humidity is high, it is easy to cause hardening and poor air permeability, which is not good for growth and development. Ridge bottom width is 75-85cm, ridge height is 25-30cm, row spacing is 95-100cm, and ridging time is 15- 20 days before transplanting. There are two ridges at the bottom of the ridge, the ridge height is 5-8 cm, the ridge height is 25-30 cm, and the row spacing is 95- 100 cm. The ridging time is 15- 20 days before transplanting. Two furrows of 5-8 cm are opened at the bottom of the ridge, and half of the prepared base fertilizer is applied into the furrows, and the ridge is ridged to 15 cm, and the other half is applied in the middle, and the ridge top is 25-40 cm wide. Trough shape, middle depression, early heat preservation and moisture retention. Before waxing, a ditch of 5-8 cm was opened in the middle of the top of the ridge, and 98% chlorhexidine was sprayed 2500 times in the ditch, and then the flat ditch was restored to its original state. Mix 40 kg of 50% acetochlor EC 100 g with water, spray it evenly on the center of the ridge, and then cover with plastic film for pressing. It is best to use 0.006-0.007 mm silver-gray aphid repellent film, which is beneficial to prevent leaf diseases. 3. Transplanting: Transplanting is the beginning of field cultivation and the key step of tobacco production. The advantages of this work are related to the success or failure of the whole production period. The time should be when the daily average temperature is stable at 12- 13 degrees Celsius. It should not be too early or too late. Prevention of freezing injury is too early, growth is slow, it is easy to happen early, and at the same time, the yield is reduced, but it is too late. Transplanting can be divided into dry planting. Either planting method is to mix100g of land with100kg of fine soil, and squeeze it into the hole, and the plant will be reduced to 50cm, that is, 1650- 1950. When sealing the soil, it is advisable that the growth point of tobacco seedlings is 2 cm higher than the topsoil. 4. Seedling protection: after transplanting, hoe and check the seedlings within three days. Due to poor quality, insect bite damage, etc. Replenish new seedlings in time and water them properly to ensure the survival rate 100%. Comprehensive control: a, two new leaves grow 6-7 days after transplanting, which is also called rooting period. It takes 98% to irrigate the roots with 2,500 times of hymexazol, and spray the leaves with 2116,600 times of strong seedlings with 500 times of aphid louse/kloc-0 and 20% virus A powder, which can effectively control damping off. B. Ten-leaf period: the temperature rose this summer. If there is too much precipitation and the humidity in the soil is high, it is the high incidence period of various diseases. Doing a good job in disease prevention during this period is the guarantee of a bumper harvest in the whole tobacco season. 2 1 16 special tobacco 600-fold killing tianda toxin 1000-fold killing tianda 2% avermectin 1500-fold solution can effectively control the occurrence and harm of various gap pests and diseases, and spraying 1000-fold killing tianda toxin every 8 days is more effective. C. Fourteen-leaf stage: it is the peak period of black shank disease and frog eye disease, and it is also the secondary period of common mosaic disease. 2 1 16 The dosage of 600-fold solution for tobacco is 2500-fold solution of 98% hymexazol, and 500-fold solution of A20% powder of virus is sprayed. D. Eighteen-leaf stage: it is the high incidence period of brown spot disease and the peak period of aphids, and powdery mildew and thrips also occur at the same time. Spraying this medicine well is the last key. 2 1 16 tobacco special type 600 times Dupont Kuaijing 2500 times and Aphid Kuaike 1500 times, which can effectively control the damage caused by the gap of pests and diseases and ensure the normal growth and maturity of tobacco. Third, the field management technology of flue-cured tobacco planting (1) check seedlings and make up seedlings. After advocating small control and large transplanting, it is necessary to water and check the seedlings. When replanting, a small amount of compound fertilizer or quick-acting nitrogen fertilizer can be applied in the hole, and poisonous bait can be applied. Advocate small seedlings to control big seedlings, make the whole field grow consistently, and achieve fullness, neatness and strong seedlings. (2) Intertillage and soil cultivation are generally 2-3 times, combined with weeding. For the first time, 7 ~ 10 days after planting, shallow hoeing, no digging, no moving roots and no covering seedlings. The second time is 15 ~ 20 days after colonization, and the nest is slightly shallow and 6 ~ 7 cm deep; Separate slightly deeper, about 10cm, and remove weeds. The third intertillage is within 25 ~ 30 days after planting, combined with the last topdressing and soil cultivation. At this time, the root system is developed and the intertillage is shallow. If the growth of tobacco plants shows the symptoms of great stamina but not yellowing at maturity, it needs to be inserted into one side or both sides of tobacco plants for proper deep tillage to cut off some roots and promote yellowing and maturity. Soil cultivation can be combined with towel tillage and weeding, and the ridge after cultivation is as high as 27 ~ 33 cm, which can play the role of soil cultivation. If only one large-scale soil cultivation is carried out, it will be carried out 25 ~ 30 days after planting. Cultivating soil too early or too late will affect the growth of tobacco plants. (3) Water management 1. Generally, the water requirement of flue-cured tobacco is less in the early stage, more in the middle stage and less in the late stage. Transplanting to clustered trees requires less water, and the stage water consumption accounts for 4% ~10% of the total water demand; The water consumption from bush to bud is the most, accounting for about 53%; About 35% after budding. Soil moisture at seedling stage should be kept at 65% ~ 70% of the maximum field capacity; 50% ~ 60% of the fruiting period; The peak period is maintained at 70% ~ 80%; 60% ~ 65% is suitable for maturity. 2. Irrigation and drainage There is abundant rainfall in the southern tobacco-growing areas, but there are also droughts from time to time. If the surface soil dryness is lower than 60% of the maximum field capacity, the ground will not recover water in the morning, and the leaves will wither during the day and will not recover at night, which indicates that irrigation is needed. Irrigation should be carried out in the evening or at night. When transplanting, sufficient water should be poured, generally 1.5 ~ 2 kg water should be poured into each hole, and 60 ~ 90 m3 water should be poured into lhm2. Under the condition of drought in early days, the seedling stage can be irrigated 1 ~ 2 times, and the water demand per time is150 ~ 300m3; Generally, as long as the soil moisture is not less than 50% of the maximum field water holding capacity at the root extension stage, there is no need to water; Watering can be done for 2-3 times in the prosperous period, with a water requirement of 1hm2 each time, about 7500m3. When the drought is severe in the mature period, watering can be done lightly for 1 ~ 2 times, and the water requirement of lhm2 is 300~450m3 each time. For point irrigation (plant irrigation) or furrow irrigation, flood irrigation or flood irrigation is prohibited. Tobacco is relatively drought-tolerant and waterlogged-tolerant, so it can't accumulate water in the field. (4) Shooting (wiping) measures must be taken in the cultivation of flue-cured tobacco with topping and bud removal for the purpose of picking leaves. Topping and bud removal can promote the growth of roots, stems and leaves, especially for increasing the weight of leaves and improving the internal quality of tobacco leaves. At present, the number of leaves left in flue-cured tobacco is about 18 ~ 22. If there is still vigorous growth when topping, 1 ~ 2 leaves can be left, otherwise 1 ~ 2 leaves should be left less. According to the development degree of inflorescence, the topping period can be divided into two stages: topping with buttoned heart and topping with budding. The first flower hits the top, and the full flower hits the top. Topping is widely used in bud stage and early flowering stage. Bud topping consumes less nutrients and the top leaves can fully develop. The top leaves of the first flower are very weak. Long smoke can reach the top when it is in full bloom. Topping should be done in sunny days, and the three leaflets under the inflorescence should be removed together with the buds. After topping, axillary buds germinate from top to bottom and grow into forked tobacco, which consumes a lot of nutrients and reduces the yield and quality. Therefore, the inhibitory buds must be thoroughly removed. Early manual removal (wiping) of flower buds is usually carried out when the flower buds are 2 ~ 3 cm long. Buds are small, tender, easy to rub, wounds are small, easy to heal, and consume less nutrients, which is beneficial to leaf growth. Apply it every 5 ~ 7 days. Using tobacco bud inhibitor can save labor, improve quality and increase yield. In recent years, In-D(Primet 250 EC) produced by Heilongjiang Tobacco Company in cooperation with Heilongjiang Institute of Petrochemical Technology and 33% EC (Accortab 330e) produced by American Cyanamide Company have been applied in China, and both of them have good bud suppression effects. The main methods of use are smearing and pouring cups. (5) preventing early flowering, drying the bottom and cultivating forked tobacco L. The phenomenon of preventing early flowering tobacco plants from flowering according to the variety characteristics or the number and height of leaves to be cultivated all the year round is called early flowering. The yield and quality of early-flowering tobacco plants decreased obviously. The vegetative growth of tobacco can be divided into basic vegetative growth period and variable vegetative growth period. The main factors to accelerate the growth of cone-shaped flower buds during the variable vegetative growth period are: low temperature. At 13 ~ 180C, the duration is 10 ~ 20 days. Low temperature. At 13- 18℃, it lasts for 10 ~ 20℃. Seedling age. The older the seedlings are, the more sensitive they are to low temperature and the easier they are to blossom early. Length of sunshine. When the temperature is below 20℃, the sunshine time is less than 8 hours. Drought, waterlogging or lack of nitrogen. These are the reasons for early flowering. To prevent early flowering, it is necessary to plant tobacco scientifically, especially pay attention to the temperature when transplanting. After early flowering, planting tobacco can be used as an emergency remedy. 2. Prevent the leaves near the ground from yellowing or wilting before the leaves of bottom flue-cured tobacco mature, which is called bottom curing. Bottom baking will seriously reduce the quality of products. Bottom drying is due to the abnormal metabolism of tobacco plants caused by harsh environmental conditions, and the growth of lower leaves is damaged. The field is seriously shaded and the humidity is too high, which is called "water dryness"; Because of the serious drought, it is called "the sky is dry and the things are dry"; In addition, nitrogen deficiency can also lead to bottom baking. Bottom baking should focus on prevention, reasonable close planting, standardized cultivation and improvement of field environment. After the bottom baking happens, pick the baked leaves in time. 3. Cultivation of flue-cured tobacco When the nitrogen nutrition level of tobacco plants is too high or the phenomenon of early flowering occurs, it is a beneficial measure to cultivate flue-cured tobacco with axillary buds. The quality of fork cigarettes is not as good as that of main cigarettes, and they are only used under special circumstances. There is a top bifurcation and a bottom bifurcation. Top dressing and topping in time, strengthen management and improve quality. The fourth is to control pests and diseases 1, mosaic. First, pay attention to field operation and tool disinfection, remove diseased plants in time and destroy them centrally. The second is to balance nutrition, improve nutritional resistance, rationally match nitrogen, phosphorus and potassium fertilizers, and appropriately increase the amount of potassium fertilizers. Thirdly, after the wheat harvest, we should avoid and control the recurrence of aphids and cut off the transmission route of the virus. Fourth, spraying 500 times solution of Bick virus wettable powder, 400-600 times solution of Jinyebao wettable powder or 0. 1% zinc sulfate and 20% virus A for control. 2, angular leaf spot, wildfire disease. First, rational fertilization and irrigation in tobacco fields to prevent excessive nitrogen fertilizer in the later period and increase the application of phosphorus and potassium fertilizer. Second, when spot disease occurs in the field, the diseased leaves should be removed in time, and 1: 150 Bordeaux solution or 2 million units of agricultural streptomycin or 50% DT500 times solution should be sprayed every 7 ~ 10 days for more than three times. 3. Climate spot disease. First, strengthen field management, increase root topdressing 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 70% thiophanate-methyl 500 ~ 1000 times solution, 50% zineb 600 times solution or 2 million units of agricultural streptomycin 500 times solution. 4. Tobacco bugs. First, adhere to the principle of "treating early and treating small" and eliminate pests before the third age (gluttony period). The second is to kill larvae and eggs, check the bottom leaves and the back of leaves, spray drugs to kill eggs when purple-brown eggs are found, and check the heart leaves and tender leaves in time for artificial killing; The third type is 65,438+0,000 ~ 65,438+0,500 times of 50% Fenthion EC, 65,438+0,000 times of 900% Trichlorfon EC, 800 times of 50% Phoxim EC and 3,000 times of 90% Wanling or Kuailing WP. Use drugs alternately to prevent pests from developing drug resistance. At the same time, local tobacco departments should warn the majority of tobacco farmers and friends that tobacco diseases and insect pests should be prevented not only as early as possible, but also scientifically, and the dynamic occurrence and problems in prevention and control should be reflected or consulted to the tobacco departments in time so as to take targeted measures to prevent large-scale occurrence of diseases and insect pests.