Tobacco is an important cash crop. It belongs to the family Solanaceae and the genus Nicotiana.The genus Nicotiana has more than 60 species, of which two are commercially cultivated for the production of tobacco. They are N.tobaccum and N.rustica.
The old doggerel says ‘Tobacco is a dirty weed, I like it.’ This demonstrated that tobacco causes addiction which chiefly consumed as a fumitory (smoking) and a masticatory (chewing) item.
This is the only commercial non-food crop that enters the world trade as a leaf;hence it is called the ‘Golden leaf’. It is prized for aroma, taste and flavor. It contains nicotine, an alkaloid,:strength of tobacco and its smoke is primarily depend on nicotine content of it.
It is used as chewing,cigarettes,cigars and other purposes. It is also used in industrial purpose in the production of Nicotine sulfate(insecticide) and Nicotonic acid(component of vitamin complex).
Origin and distribution
Nicotiana tobaccum is a native of western hemisphere from Mexico southward. The type of tobacco presently being cultivated evolved in Mexico and Central America. The plants were cultivated by red Indians at the time of discovery of America by Christopher Columbus in 1492. The Nicotiana rustica is originated in highlands of Peru, Equator and Bolivia. It is popular throughout the world ,in Nepal its cultivation is chiefly in eastern part of the country.
Soil requirement- Generally, soil with good surface and internal drainage, adequate moisture retention and aeration is preferred for its cultivation.
Light, Temperature ,Rainfall,Relative humidityplays an important role in its cultivation
It is widely classified accordingly with different basic.
A)On the basic of cultivated species-N.tobaccum and N.rustica
B)On the basic of botanical feature and ecotypes- American, Oriental ,Southern tobacco ,Asian tobacco and Island tobacco.
C)On the basic of curing method- Flue cured tobacco, fire cured tobacco, Air cured tobacco and Sun cured tobacco.
D)Cigar tobacco- Cigar filler, Cigar binder and cigar wrapper.
Cropping System -Tobacco is susceptible to root-knot nematodes and other root and collar rot pathogens.So,nematodes susceptible crops such as cowpea,soyabean etc.should not be included in rotation. Crops like corn ,cotton etc. are best for succesful cultivation of tobacco in rotation.
Nursery raising-Tobacco seeds are very small and not sown directly ,seedlings are raised in trays or open nurseries and then transplanted.
Plant management-It includes practices like soil loosening , nutrient management,irrigation,weeding,top -dressing ,topping and desuckering..
Some diseases and pest of tobacco
• Damping off
• Black shank
• Brown spot
• Leaf curl
Brown spot- Symptoms
• Small, circular, target-like spots on lower leaves; lesions are usually surrounded by a bright yellow halo; lesions enlarge and coalesce; centers of lesions dry out and drop from leaf giving foliage a ragged appearance; if variety of tobacco being grown is susceptible to the disease then spots may also appear on stalks and suckers; if spots girdle stems then the plant may be killed
• Rotating crop away from tobacco can help to reduce the levels of inoculum in a field; stalks and roots left after harvest should be removed and destroyed; control nematodes in the soil; ensure plants have adequate potassium available to promote vigorous growth.
• Rapid yellowing and wilting of the plant proceeds plant death; dark brown to black sunken lesion is usually present on the stalk of the plant close to the soil line; lesion may extent up the stalk turning it black; splitting open stalks reveals darkened pith in discrete discs.
• Rotating the crop away from tobacco for at least one year will help to reduce levels of inoculum; plant tobacco varieties that have some degree of resistance to the disease; apply appropriate fungicides to the soil; plant tobacco in well draining soils; destroy stalks and roots immediately after harvest to reduce overwintering sites for the pathogen; control nematodes in the soil.
• Alternating light and dark green patches on the leaves; leaves turning brown and drying out.
• Plant resistant tobacco cariteies; remove and destroy any infected plants; disinfect tools thoroughly; wash hands thoroughly after use of tobacco products before handling plants; avoid having tobacco products on person when working with tobacco plants
• Tobacco caterpillar
• Stem borer
• Ground beetle
• Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants.
• If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high – plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use.
• Feeding damage to leaves or leaves stripped from plant; heavy infestation may result in damage to fruit appearing as large open scars; large green caterpillars may be spotted on plant; caterpillars may reach in excess of 7.5 cm (3 in) in length and possess a spike at the end of their body; most common species have 7 diagonal stripes on sides or 8 v-shaped markings on each side; single eggs may be present on leaves and measure approx 1.3 mm in diameter; eggs are in initially light green in color and turn white prior to hatching.
• Hand pick larvae from plants leaving any parasitized larvae behind to promote populations of natural enemies (these larvae can be distinguished by the presence of white, oblong-shaped cocoons on their backs); sprays of Bacillus thuringiensis are organically acceptable and highly effective.
• Large or small holes in leaves; damage often extensive; caterpillars are pale green with a white lines running down either side of their body; caterpillars are easily distinguished by the way they arch their body when moving; eggs are laid singly, usually on the lower leaf surface close to the leaf margin, and are white or pale green in color.
• Lopper populations are usually held in check by natural enemies; if they do become problematic larvae can be hand-picked from the plants; an organically acceptable control method is the application of Bacillus thuringiensis which effectively kills younger larvae; chemical sprays may damage populations of natural enemies and should and should be selected carefully
Harvesting-The times of harvesting differ with the types of tobacco. The tobacco leaves do not ripe uniformly ,the first to ripe are lower old leaves than middle and upper leaves.Leaves are ready to harvest when they turn into light green to slightly yellow color.Usually harvesting start after 90-120 days of transplanting. It includes two methodmainly Priming and Stalk-cut method.
Curing -The leaves of tobacco are cured after harvesting. Different methods of curing are adopted for different types of tobacco.Flue curing, air curing fire curing etc. are some methods of curing it..
Gauradaha Agriculture Campus .