Diseases

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Common Tobacco Diseases

 

Some of the most common diseases affecting the tobacco are as follow:

Seedbed Damping Off (Fonte de semis)
Fungicidal Phytotoxicity
Nitrogen Deficiency
Field Herbicide Injury
Potato Virus Y (PVY)
Cucumber Mosaic Virus (CMV)
Frog Eye
Weather Fleck
Powdery Mildew
Sooty Mould
Curing Cucumber Mosaic Virus (CMV)
Barn Rot
Mould - Flue-cured tobacco
Mould -Air-cured tobacco
Pole Rot
Storage Lasidioderma serricorne

 


 

Damping Off (Fonte de semis)

Damping off      Damping off

Damping-off is a general term applied to the rotting of seeds, germinants, and succulent seedlings. There are two stages: pre-emergence damping-off kills seeds and germinants before they emerge, post-emergence damping-off affects young seedlings after emergence. Both diseases occur in bareroot and container nurseries throughout the province. In containers, damping off pathogens are often introduced as seed-borne inoculum, or via contaminated water or growing media. In bareroot nurseries, losses are mainly caused by soil-borne fungi, especially Fusarium and Pythium.

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Fungicidal Phytotoxicity

Phytotoxicity      Phytotoxicity

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Nitrogen Deficiency

The two most common symptoms of N deficiency in tobacco seedlings are: (1) leaves develop a light or pale yellow color, and (2) plants become stunted, showing little growth and vigor. Similar symptoms may develop from a lack of water during dry weather. N deficiency in tobacco seedlings is not common if recommended amounts of N are properly applied to plant beds. However, excessive rainfall may create the need for additional N. Also, the use of ammonium or organic forms of N on plant beds fumigated in the spring may result in N deficiency.

Source: http://www.forestryimages.org/

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Herbicide Injury

Herbicide Injury

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Potato Virus Y (PVY)

PVY

Potato Virus Y (PVY) is a plant virus that is spread by aphids (insects) and infects potatoes, tomatoes, tobacco, and other plants. It is not harmful to humans but causes a disease that may result in crop losses. There are strains of the virus that are much more harmful to tobacco even though tomato and other plants may be symptomless carriers.

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Cucumber Mosaic Virus (CMV)

CMV

CMV is another widespread virus. It was first reported in the 1900's in several places in North America. It is now considered to be worldwide. It has an very wide host range, which includes tomato, carrot, celery, cucurbits, legumes, lettuce, spinach, pepper, dahlia, delphinium, columbine, geranium, petunia, phlox, zinnia and viola, and many weeds, such as chickweed, pokeweed and milkweed.

Cucumber mosaic virus (CMV) causes plants to become yellow, bushy and very stunted. Leaves may be extremely distorted and malformed. Leaflets are often very narrowed; this is called "shoestring". Often the leaves on one portion of the plant (e.g., the top or the bottom) show severe symptoms, while those higher or lower in the plant are less affected. Other leaf symptoms include a yellow and green mottling similar to tobacco mosaic symptoms. Severely affected plants produce few fruit.

Cucumber mosaic is spread in a non-persistent manner by aphids. It is not spread by seed. Control weeds, many of which are host species. Surrounding fields with a taller, non-susceptible plant, such as corn, may help shield the plants from aphids blowing in from other areas. See current recommendations for control of aphids, although it is generally considered that insecticides will not control this disease. The aphids pick the virus up from the plants in about a minute and are able to spread it immediately. Insecticides take longer than this to kill the aphids. Mineral oil sprays can be used to prevent the virus from being transmitted.

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Frog Eye

Frog Eye

Frogeye may develop on the leaves of tobacco in the plant bed, field, or barn. The spots on the leaves are quite distinct, typically circular, with a reddish-brown margin and tan or grey colored papery centers in which black masses (fruiting bodies) of the fungus may be found. Frogeye usually occurs on the lower leaves but moves up the plant as the season progresses, especially as the nitrogen supply is depleted. Sudden development of large dead in the upper leaves may occur near harvest. Frogeye may be confused with brown spot, wildfire, angular leaf spot, weather fleck, and physiological spotting, and it requires microscopic examination for diagnosis. Green spots on the leaves of cured tobacco may be the result of frogeye infection near harvest.

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Weather Fleck

Weather Fleck

Leaf spots are often the result of infection from disease or from unbalanced nutrition, such as potassium or phosphorus deficiency.  Other leaf spots are caused by air pollution.  Ozone is a natural component of the atmosphere and high amounts often cause leaf spots on tobacco. 

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Powdery Mildew

Powdery Mildew

The fungus (Erysiphe cichoracearum) forms a white mealy coating over the leaf surfaces and from this sign the disease gets its name. It is composed of morphologically indisguishable strains that differ in pathogenicity.

It first appears as felt-like patches which enlarge rapidly on the underside of the leaves and soon cover the entire lower leaf surface.  On the upper leaf surface brown spot appear.  Affected leaves become thin and papery and when cured are of little value.

Sometimes the black, spherical perithecia (80 - 140 microns in diameter) of the fungus and chains of conidia form on the leaf surface and are easily seen with a hand lens.

The disease is controlled by proper fertilisation and planting early to avoid low temperatures.  Fungicides are also used. Karathane (dinitro 1-methyl heptyl phenyl crotonate) applied 3-4 times at 12-15 days interval gives 86-90% control with no adverse effect on quality. Wettable sulphur has also given good control. The systemic fungicide, benomyl is widely used in several countries with good success although there is evidence of resistant strains developing.

Source: Disease of tobacco by G. B. Lucas

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Sooty Mould

Sooty Mould

 

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Cucumber Mosaic Virus (CMV)

CMV is distributed worldwide and the symptoms it causes are easily mistaken for Tobacco Mosaic Virus (TMV) as it occurs frequently in areas where vegetables are grown. It has a wide range of hosts.

Typical mottling and mosaic patterns appear, sometimes accompanied by stunting and narrowing and distortion of the leaves. Severe strains may cause interveinal discolouration and the oak-leaf pattern of necrosis the lower leaves.  Mosaic-burn or sun-scald frequently appears on the upper leaves of infected plants.  Mild strains cause only a faint mottling of the leaves.

 

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Barn Rot

There are several types of barn rot, and at least 3 decay fungi are are involved. The name Pole rot is used to refer to all forms of rot that affect curing tobacco while hanging on poles. This distinguishes it from other rots that may occur in the bundle, the case or in the field. 

This is a serious disease and accounts for greater loss to tobacco growers than any other disease. The main fungi is called Botrytis cinerea and Rhizopus arrhizus. Outbreaks are sporadic, thus serious losses are confined to relatively few barns in any one season.

Four principle types of leaf decay that occur in curing process have been recognised, namely stalk rot, web rot, vein rot and freckle rot. These may intergrade and do not represent 4 distinct diseases

The most effective and easy way to prevent this disease is to get rid of the excess moisture and keep the leaf surfaces free of water, especially in the early stages of curing. Regardless of high temperature, it will not occur unless high humidity prevails continuously for more than 24 hours, and the danger is not great until the humidity reaches 85-90%. High humidity can be prevented by ventilation.

The severity of barn rot, caused by R. arrhizus, can be reduced by soaking tying twine, or by spraying butts of leaves with 0.05% dichloran (2:6-dichoro 4-nitoniline) suspensions.

Source: Disease of tobacco by G. B. Lucas

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Mould - Flue-cured tobacco

Mould

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Mould -Air-cured tobacco

Mould

 

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Pole Rot

Pole Rot

The name Pole rot is used to refer to all forms of rot that affect curing tobacco while hanging on poles. This distinguishes it from other rots that may occur in the bundle, the case or in the field. 

This is a serious disease and accounts for greater loss to tobacco growers than any other disease. The main fungi is called Botrytis cinerea and Rhizopus arrhizus. 

 

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Lasidioderma serricorne

 

It eats like a pig, breeds like a bunny, lives fast and dies young. It worships tobacco and heat. It's Lasioderma serricorne, better known as the tobacco beetle

Known by entomologists as "cosmopolitan" insects, tobacco beetles are found all over the world, but only in environments where the temperature exceeds 65 degrees Fahrenheit. Adult beetles measure about two to three millimeters long. They have wings and can fly, but live only for an average of two to four weeks. Brownish-red, they have serrated antennae for touching and smelling; these antennae steer them toward the warm habitats where they nest and breed.

Like many other beetles and insects in general, tobacco beetles have a four-stage life cycle--egg, larva, pupa and adult--that lasts about 10 to 12 weeks. The female adult can chew its way through paper or tobacco leaf, and finds in cigars a suitably warm environment to lay its eggs, small white ovals that are too small for the human eye to detect. The eggs, up to 100 per birth cycle, hatch within six to 10 days, giving birth to the larvae. The larvae present the most danger to tobacco.

"The larvae are what eat the tobacco," says Ridge-O'Connor. "They need tobacco or other foods stored in a suitable temperature to grow into the pupa and adult stage."

White, soft and prickly, larvae can be up to four millimeters long. The larval stage is the beetle's longest phase of life, averaging six to 10 weeks. It's followed by a one- to two-week pupal stage, during which a protective cocoon grows around the insect. Finally, more than two months after the eggs have been laid, the tobacco beetle emerges from its cocoon for its brief life as a fully formed adult.

One common myth regarding tobacco beetles is that they live solely off tobacco. Not true. They're equally attracted to other plants and food products stored within their desired temperature range (65 degrees Fahrenheit and warmer). Tobacco beetles infest stored products, both edible and inedible, including spices (such as paprika and coriander), rice, dry pet food, seeds, pharmaceuticals, books, leather, coffee beans, furniture, upholstery, peanuts and yeast.

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