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Tobacco Mosaic Virus
The tobacco mosaic virus can attack a wide range of plants, including tomato, pepper, eggplant, tobacco, spinach, petunia, marigold, and our beloved herb marijuana.
On marijuana the virus infection causes light and dark green mottled areas on the leaves.
The dark green areas tend to be somewhat thicker than the lighter portions of the leaf. The leaf mottling is seen more easily if the affected plant surface is partially shaded.
Stunting of young plants is common and often is accompanied by a distortion and fern-like appearance of the leaves. Older leaves curl downward and may be slightly distorted.
Certain strains of the virus can cause a mottling, streaking and necrosis of the buds. Infected plants are not killed, but they produce poor quality buds and low yields.
Tobacco mosaic, is incited by a virus. The tobacco mosaic virus is very stable and can persist in contaminated soil, in infected plant debris, on or in the seed coat, and in manufactured tobacco products. The virus is transmitted readily from plant to plant by mechanical means.
This may simply involve picking up the virus while working with infected plant material, then inoculating healthy plants by rubbing or brushing against them with contaminated tools, clothing, or hands. Aphids are not vectors of the virus, although certain chewing insects may transmit the pathogen.
Solution: Virus diseases cannot be controlled once the plant is infected.
Therefore, every effort should be made to prevent introduction of virus diseases into the garden.
Sanitation and cleanliness is the primary means of controlling virus diseases.
Infected plants should be removed immediately to prevent spread of the pathogens.
The use of tobacco products during cultural practices should be avoided to prevent inoculation of plants with the tobacco mosaic virus.
Those people using tobacco or working with infected plant material should wash their hands thoroughly in soapy water before handling your plants."
http://www.growweedeasy.com/bugs-pests-symptoms-marijuana-grow#tobacco-mosaic-virus