What is tobacco mosaic?

Tobacco mosaic is a common disease in tobacco planting. How much do you know about this pest? Let me introduce the introduction of tobacco mosaic to you, hoping to help you.

Brief introduction of tobacco mosaic disease

Tobacco mosaic has two symptoms.

1. Common mosaic disease: infected by virus, young leaves begin to get sick first, mesophyll along veins turns yellow and bright veins appear. Then the dark or light parts gradually expand, forming yellow-green mottling (mosaic); In severe cases, the leaves become uneven in thickness, forming bubble spots, the leaf edges curl backwards, the leaves shrink and twist, and some are serrated or banded. In the early stage, plants were seriously dwarfed, internodes became shorter, and trees and leaves could not be opened.

2. Cucumber mosaic disease: infected by virus, the veins are transparent at the beginning of the disease, and then become mosaic, the leaves become narrow and twisted, and the surface hairs fall off and lose luster. Some diseased leaves often curl upward, some have yellow-green or dark green blisters, some have brown necrosis in lateral veins, or dark brown lightning necrosis along veins. The plant is obviously dwarfed and the root system is stunted. Dead leaves often appear? The ignition point of the mosaic? .

Control methods of tobacco mosaic disease

Tobacco mosaic is one of the three major diseases of tobacco, which is widespread in all tobacco-growing areas of our province. When the disease occurs in seedling stage or early field stage, the yield can be reduced by 30% and the economic loss can reach 50%-70%. After topping, the disease has little effect on yield, but has great influence on quality. The disease is caused by many viruses, mainly common mosaic and cucumber mosaic in production.

First of all, symptoms

1. Common mosaic disease: infected by virus, young leaves begin to get sick first, mesophyll along veins turns yellow and bright veins appear. Then the dark or light parts gradually expand, forming yellow-green mottling (mosaic); In severe cases, the leaves become uneven in thickness, forming bubble spots, the leaf edges curl backwards, the leaves shrink and twist, and some are serrated or banded. In the early stage, plants were seriously dwarfed, internodes became shorter, and trees and leaves could not be opened.

2. Cucumber mosaic disease: infected by virus, the veins are transparent at the beginning of the disease, and then become mosaic, the leaves become narrow and twisted, and the surface hairs fall off and lose luster. Some diseased leaves often curl upward, some have yellow-green or dark green blisters, some have brown necrosis in lateral veins, or dark brown lightning necrosis along veins. The plant is obviously dwarfed and the root system is stunted. Dead leaves often appear? The ignition point of the mosaic? .

Second, the law of occurrence

1. Common mosaic disease: This virus can survive for a long time in patients and disabled people. Mainly mixed in soil, fertilizer, seeds and other sick people, as well as some toxic hosts such as tomatoes, rape, mustard or perennial weeds. It spreads through contact with juice, that is, it invades the host from the micro-wound of mechanical friction, and spreads through people, wind, insects and other media: from seedbed to vigorous growth susceptible to diseases, the resistance is enhanced after topping. 18? The temperature of 30℃ is most suitable for onset. Close to towns, flue-cured tobacco houses, purchasing points, roadsides, vegetable fields and tobacco fields used as tobacco fields and vegetables are seriously ill; Poor management of fertilizer and water after transplanting, thin and hard soil in tobacco fields, poor drainage and poor growth of tobacco plants lead to serious diseases.

2. Cucumber mosaic: The virus cannot survive in dry tobacco leaves under natural conditions. Winter mainly overwinters in vegetables, vegetable seeds or perennial weeds. The next spring, it was mainly caused by the spread of tobacco aphids. Therefore, when there are many weeds, tobacco fields are close to vegetables such as cucumbers and tomatoes, high temperature and drought, and aphids occur in large numbers, the disease is serious. If nitrogen fertilizer is applied too much, the disease will be very serious when the soil is barren, hard and sticky.

Third, prevention and control technology

1. Select high-yield and disease-resistant varieties. Such as Kirk 176, K394, g346, K326 and NC series.

2. Optimum seedbed and reasonable rotation. The seedbed should be a field with good soil fertility, sheltered from the wind and sunny, convenient for irrigation and drainage, and far away from vegetable fields, curing houses and hanging sheds. At the same time, paddy-upland rotation of tobacco and rice should be carried out in the field, which can greatly reduce the pathogen and harm.

3. Soil disinfection. Plus the sun in winter. Seedbeds can generally be incinerated and disinfected, and severely ill areas can be fumigated and disinfected with methyl bromide, and at the same time, nutrient soil should be selected. 60 kilograms of lime can be used to clean up and disinfect the fields. It can eliminate pathogens, pests and weeds in the soil.

4. Strengthen cultivation management. Sow and plant early in time, cultivate in single ridge and high ridge, and cultivate healthy seedlings without disease; Rational fertilization and scientific water management can promote early growth and rapid development, and enhance the disease resistance of chlorophytum plants.

5. Clean up the fields and intertillage and weed in due course. Remove foot leaves, rotten leaves, diseased leaves and lobules in time. Eliminate weeds around rural areas in the field and burn them centrally; It is forbidden to use farm manure containing poisonous tobacco plant residues, tobacco scraps, tobacco stalk ash and garbage soil in front of and behind the house as nutrient soil or fertilizer in tobacco fields. At the same time, pay attention to the field operation, according to the order of healthy plants first and then diseased plants, to avoid mechanical damage and reduce human contact and transmission. After tobacco leaves are harvested, all tobacco fields should be thoroughly cleaned, and tobacco stems and diseased plant residues should be burned centrally to remove germs.

6. Control aphids in time and cut off the source of the virus. You can choose 40% omethoate.

1000? 1500 times solution or 20% metronidazole 3000-4000 times solution, 50% pirimicarb 800? 1500 times spraying liquid. If the temperature is high, the weather is dry, and the number of aphids is large, it should be controlled by continuous spraying. At the same time, it can also be popularized to cultivate with silver plastic film, which has obvious effect of expelling aphids and is beneficial to avoid the susceptible period of one month after transplantation.

7. Chemical control. Spraying 1 time in the big cross stage, mature stage, returning stage and clumping stage of the seedbed respectively. The medicament can be selected from 20% virotoxin B500 times solution or 1.5% Phytophthora 800- 1200 times solution, 1% virus antibody and 83? 1 inhibitor 100 times solution spraying.

Tobacco planting technology

I. Environmental conditions for tobacco growth

1, temperature: tobacco is a thermophilic crop, and the ground temperature is 8? All plants can grow in the range of 38℃, and the optimum temperature for growth and development is 25? 28℃, 2 degrees below zero? 3C, tobacco plants will die. The underground part is at 7? It can grow at 43℃, but the optimum temperature is 365438 0℃. The optimum temperature for seed germination is 24? 29℃, minimum temperature 7.5? 10C, the highest temperature is 35C. 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, the temperature should not be lower than 65438 00℃, and the ideal daily average temperature of leaf maturity should be around 24℃ for 30 days, so as to 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 capacity at the seedbed stage, and it is 10 before transplanting. 15 days to stop water and harden seedlings. Transplanted to seedling stage, the leaf transpiration is small, and the average daily water consumption is 3.5? 6.4 mm daily average water consumption 6.6? 7.9 mm, the soil moisture should be kept at 60% of the field capacity; Below 40%, the growth will be hindered, and above 80%, the root growth will be poor, which is not good for the later growth. The average daily water consumption is 7. 1? 8.5 mm, the soil moisture should be kept at 80% of the field capacity. During this period, if there is water shortage, growth will be hindered. If there is a long-term drought, there will be early flowering or early drying up. From germination to maturity, the average daily water consumption is 5.5? 6. 1 mm, the soil moisture should be kept at 60% of the field capacity, and the moisture is slightly less at this stage, which can 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. The growth period of flue-cured tobacco requires sufficient sunshine, but it is not very strong, and the daily sunshine time is 8? 10 hour is suitable, especially in the mature period, and sufficient 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 strict. Red soil is the best, followed by red loess, sandy soil and mixed soil, and tidal soil (black soil) is the worst.

5. Weather phenomenon: gale and hail weather do more harm to tobacco leaves than any other crops, which may cause 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 planting management

1, seedling raising: tobacco seeds should be placed in 15 before germination. The sun basked at 20℃ for 2? 3 days, improve the germination potential and germination rate of seeds. To cultivate strong seedlings, the first is to adopt the new technology of double-layer film paper tube, with a diameter of not less than 4 cm and a height of 6? 7 cm, 625 seedlings per square meter, 4 mu of tobacco field can be planted 1 bed 10 square meter. The second is to prepare nutrient soil, with 60% field soil and 40% decomposed pig manure as the substrate, and the need for each border is about 0.8? 1 m3, disinfected and then mixed with compound fertilizer 3? Four kilograms.

Third, timely early sowing and early transplanting can increase yield by 20% and improve quality by 25%. Huanghuai tobacco-growing areas should be planted from spring to mid-February. Four, seedbed management, due to the low temperature when sowing, vulnerable to low temperature hazards, should be adjusted in time according to the requirements of tobacco seedling growth on temperature and humidity. Generally, there are two intervals, the first time is in? Intertemporal? After that, the seedling spacing is 1.5? 2 cm, the second (fixed) seedling with 4? When there are 5 true leaves, the seedling spacing is 6? Eight centimeters.

2. Transplanting: timely and early planting is the key to producing high-quality tobacco leaves. The best transplanting period in Huanghuai tobacco-growing areas should be completed before Qingming to Grain Rain. The planting density should be controlled at per mu 1200? 1300 strains. Planting tobacco with plastic film mulching can not only increase temperature and preserve moisture, but also improve the drought and waterlogging resistance of tobacco plants and prevent tobacco black storm. If it rains thoroughly before transplanting, it can be covered with plastic film in time to keep warm after the rain. If it doesn't rain, you should bring water from the soles of your feet when planting cigarettes, and cover them tightly with plastic film after planting cigarettes (if you plant cigarettes before and after Qingming Festival, because the temperature is low, you can cover the seedlings with plastic film first, and then cut the plastic film after the temperature is stable, take out the tobacco seedlings and seal the film at the roots to prevent water loss).

3. Field management: The most prominent problem in flue-cured tobacco production is the contradiction between yield and quality. Generally speaking, the higher the output, the worse the quality, but not the lower the output, the better the quality. Therefore, management should strive to stabilize production and ensure quality.

① Suitable fertilization: base fertilizer is the main fertilizer, and new balanced fertilization technology is adopted. Before transplanting, the amount of pure nitrogen fertilizer per mu was 6 kg in low-fertility field, 5 kg in medium-fertility field and 3? 4 kg, and the ratio of NPK fertilizer is 1: 2: 3. When fertilizer deficiency is found in the middle and late stage, foliar spraying is used for topdressing.

(2) timely irrigation and drainage: under the condition of drought in tobacco field during the critical period of tobacco water demand, sprinkler irrigation 1? Doubling it can increase the yield by 8. 1? 43. 1%, which improves the quality. If the tobacco field is flooded 1? Will the output decrease by 47.8 in 2 days? 65%。 Pay attention to ditch cleaning and drainage in low-lying tobacco fields or rainy seasons.

③ Pay attention to intertillage and soil preparation: intertillage in time under drought conditions is of great significance for water conservation. Timely intertillage after rain can reduce soil moisture, increase soil permeability, increase ground temperature and promote root growth. Farming can also eliminate weeds and reduce pests and diseases. Combined with intertillage, timely soil cultivation can promote new roots, expand the ability to absorb water and fertilizer, be beneficial to drainage and waterlogging prevention, and enhance the ability to resist drought, wind and lodging.

④ timely topping and bifurcation removal: topping and bifurcation removal can not only increase production by 365,438+0? 49%, or the main way to improve the quality of tobacco leaves. Topping should generally be done in two times according to the number of leaves left, so as to promote the orderly growth and uniform yellowing of tobacco plants and facilitate baking. The branches should be cleared in time.

⑤ Strengthen pest control: give priority to prevention, and combine chemical control with manual killing.

3. Mature harvesting is one of the important links of high-quality tobacco production. The characteristics of tobacco ripening are: the leaves change from green to yellow-green, the hairs on the leaves fall off, and the angle between leaves and stems increases (about 90 degrees). Only when the main veins of the lower leaves are white, the branches of the middle leaves are white, and the main branches of the upper leaves are white, and yellow spots appear on the leaves, can they be harvested and baked.

Control methods of tobacco and cucumber mosaic disease

Cucumber mosaic disease is the most common and universal disease in tobacco virus disease. The virus is mainly transmitted by aphids and becomes popular with the migration of aphids. The disease often occurs in the stage of slow seedling growth after transplantation, which often leads to the stagnation of plant growth and development and affects yield.

At the beginning of the disease, the veins are transparent, and after a few days, they become mosaic, the leaves become narrow and twisted, and the epidermis falls off and loses its luster. The diseased plants showed dwarfing and poor root development.

The prevalence of cucumber mosaic disease is closely related to the number and activity of aphids. According to the investigation in Huanghuai tobacco-growing areas, there were two migration peaks of Myzus persicae during the growth of tobacco seedlings, the first was from late March to early April, and the second was from May 10 to 25 after transplanting. Generally, the disease of Myzus persicae in the field is the most serious after it enters the peak migration period 10 days.

Because tobacco and cucumber mosaic diseases are mainly transmitted by aphids, controlling aphids is the key to control the diseases. Silver-gray plastic film is often used to cover aphids in production. In addition, measures such as cultivating strong seedlings, deeply planting tobacco, strengthening intertillage and cultivating soil, and scientifically fertilizing and watering can also reduce the occurrence of diseases. Chemical control is generally used in seedbed stage and half a month after transplantation for 2? Zinc sulfate is mixed with zinc sulfate once and sprayed for 2 ~ 3 times. When tobacco aphids occur, it is necessary to use pesticides with strong knock-down ability, such as one-time cleaning, to repel aphids and prevent diseases.