How to prevent and control tobacco mosaic virus? A detailed explanation of the latest methods
Tobacco mosaic virus occurs commonly in tobacco-growing regions around the world, and is found in both the northern and southern tobacco-growing areas of China, with the southern tobacco-growing areas suffering more severe damage. It can occur from the seedling stage through the harvest stage. The incidence rate of plants in the field is generally 5-20%, and in individual fields it can reach as high as 90-100%. Losses from early infection can reach 50-70%, or even total crop failure. Now let us take a look at the prevention and control methods for tobacco mosaic virus!
Damage Symptoms
After a tobacco plant is infected, the lateral veins and branch vein tissues of the young leaves become semi-transparent, and the mesophyll tissue on both sides of the veins gradually turns pale green. The virus multiplies in large numbers within the leaf tissue, causing some mesophyll cells to enlarge or increase in number, resulting in uneven leaf thickness and alternating yellow and green colors, forming a mosaic pattern. Later, the mosaic mottling becomes more pronounced, and large dark brown necrotic spots appear, especially on the middle and lower old leaves. Severely affected leaves become shrunken, deformed, and distorted. Plants infected early have shortened internodes, are severely stunted, grow slowly, cannot flower and set seed normally, and are prone to shedding. Capsules that do develop are small and shrunken, contain few and small seeds, and most cannot germinate.
Conditions for Occurrence
Common tobacco mosaic virus mainly occurs from the seedbed stage to the budding stage in the field. Temperature and light greatly affect the spread and epidemic speed of the disease. High temperature and strong light can shorten the incubation period. Continuous cropping or intercropping with Solanaceae crops increases the sources of the virus, significantly increasing the incidence rate and severity of the disease. Unsanitary cultivation practices are an important cause of epidemics. Touching between diseased and healthy plants, applying undecomposed organic fertilizer, and cultivating soil carrying the virus can all aggravate virus transmission. Fields with compacted soil, dry climate, and severe nematode damage have more severe disease incidence.
Prevention and Control Methods
1. Select disease-tolerant varieties with strong growth vigor, fast development, and adaptation to local conditions, such as Liao 44, 6315, Guanghuang 54, 176, Nc89, G80, 8611, etc., and pay attention to breeding highly resistant varieties. Implement crop rotation, do not intercrop or relay-crop with Solanaceae plants, and preferably rotate with gramineous crops for 2-3 years. If mosaic virus appears, promptly apply quick-acting fertilizer, earth up and water, and promote stem elongation and leaf expansion to reduce disease damage.
2. The seedbed should be selected from plots where tobacco and Solanaceae plants have not been grown for more than 2 years and far from vegetable fields. Use seeds collected from disease-free plants in disease-free fields, or soak seeds in 0.1% silver nitrate or 0.1-0.2% zinc sulfate, or 0.1% trisodium phosphate solution for 10 minutes to remove virus from the seed surface, and rinse repeatedly after soaking. Before thinning and final thinning of seedlings, wash hands thoroughly with soap. During operations, manage healthy seedlings first, and promptly remove diseased plants when found.
3. Strengthen field management. Strictly prohibit transplanting diseased tobacco seedlings into the field. Manage healthy plants first and diseased plants afterward. Do not smoke during operations, and do not repeatedly walk through and touch the tobacco field. Apply sufficient nitrogen, phosphorus, and potassium fertilizer, and promptly spray various trace element fertilizers to improve plant disease resistance. After transplanting, properly harden seedlings, and irrigate critical water at the end of the rosette stage to promote plant growth.
4. In the early stage of disease, spray with 2% amino-oligosaccharin 6000-fold dilution, or Gaoke 32% moroxydine hydrochloride-nucleoside 800-fold dilution, or 1.5% plant virus inhibitor emulsion 1000-fold dilution, or 10% Virus King wettable powder 600-fold dilution, or 20% Huayening wettable powder 300-500-fold dilution, which can play a role in preventing and alleviating virus damage.
5. Aphids play a decisive role in the transmission of common tobacco mosaic virus. On tobacco, they generally reproduce 15-17 generations by parthenogenesis and viviparity. Therefore, for aphid control, concentrated spraying should be carried out in March to April each year on surrounding peach orchards, vegetables, weeds, and other areas to kill tobacco aphids that have already hatched or are hatching and reviving, thereby achieving the purpose of prevention.