Tobacco Mosaic Virus

IDENTIFY, PREVENT, TREAT TOBACCO MOSAIC VIRUS

Tobacco Mosaic Virus is not a common tomato disease in the UK however many gardeners suspect that it may be affecting their tomato plants because initially it shows very similar symptoms to many nutrient deficiency problems and weed-killer overspray. This article aims to help you positively identify cases of Tobacco Mosaic Virus where it does exist or on the other hand suggest much more likely causes of the symptoms.

The Tobacco Mosaic Virus is found in many parts of the world and affects tomatoes, cucumbers, peppers, potatoes, dahlias, many other plants including, of course, tobacco plants. It was the first plant virus to be identified and has been investigated in minute detail for the past 80 years.

SYMPTOMS OF TOBACCO MOSAIC VIRUS IN TOMATOES

The symptoms are listed below in the order in which they normally occur:

  1. Small patches, lighter than normal green, brown and yellow appear on the leaves. These are the earliest symptoms.
  2. Those patches on the leaves described above have been taken over by the virus and a side-effect is that the leaves may appear to be smaller than normal. This is caused by the plants photosynthesis process being disrupted.
  3. The whole plant may also be slow to develop after infection and is often smaller and generally less healthy looking.
  4. Because this is a virus with no clear lifecycle it can infect the plant at any stage of its life. If fruit develop, their skins will have bronze coloured patches on them.

Tomato plant leaf with Tobacco Mosaic Virus
Tobacco Mosaic Virus on tomatoes

Tobacco Mosaic Virus is often mistaken for other tomato plant problems. Mineral deficiencies, aphid damage, nitrogen deficiency, large variations in temperature and weed killer over-spray are common examples. If you suspect your plant may have Tobacco Mosaic Virus it’s a difficult balancing act when considering what to do. Infected plants should be pulled up and burnt to avoid further infection but you don’t want to do this if, in reality, the symptoms are caused by something like a mineral deficiency or aphid damage.

Tobacco Mosaic Virus (TMV) on tomatoes is rare in the UK, I’ve been an enthusiastic gardener and allotment holder for thirty years and have never seen it and never met any one who had first hand experience of it. With that fact in mind here is how I would proceed if I had a suspicion that this virus had attacked my tomatoes, but every person must make their own mind up.

  1. Do any other plants (including ornamentals) suffer from the same type of damage to the leaves? If yes, then suspect TMV. It infects a wide variety of plants including some which are considered weeds. Plants need to be handled
  2. Look carefully at the damage on the leaves. the word “mosaic” is key to diagnosing this disease, another word to describe the appearance would be “mottled”. If the damage on your plant’s leaves is mainly around the edges and it’s solid rather than mottled then it’s probably not TMV, more likely a deficiency, wind burn or temperature variation.
  3. If the plants have produced tomatoes which have lighter patches / marbling on them this also would indicate TMV.

If you still suspect TMV then remove the worst affected leaves (and burn them) then give the plants a light general purpose feed. To ensure the damage is not from aphids examine¬† the underside of a couple of leaves with a magnifying glass and check for them. If they are present, treat them as per our article on aphids. Finally, to rule out the rather more common problem of magnesium deficiency add 1 tablespoon of Epsom Salts to a gallon of water (4.5 litres) and water in around the plants. Now wait two weeks and examine the new foliage. If that looks disease free then you haven’t got TMV. If it looks diseased in the same way then you may well be one of the rare cases of TMV amongst UK gardeners. Read the rest of this article though to get a feel of what causes this disease and a little more about how it’s spread.

HOW TO TREAT TOBACCO MOSAIC VIRUS

There is no cure for Tobacco Mosaic Virus, diseased plants should be dug up, roots and all, then burnt. Prevention is the only measure you can take with this disease.

There are a few things you can do to prevent Tobacco Mosaic Virus and these are listed below:

  1. Practice good hygiene throughout the entire growing season. Remove decaying leaves from the plant and the surrounding soil.
  2. Burn all parts of infected plants, never put them on the compost heap and do not dig them into the soil. Wash your hands thoroughly and disinfect all gardening implements after handling infected plants.
  3. Regularly inspect plants for signs of TMV infection.

LIFECYCLE OF TOBACCO MOSAIC VIRUS

It may help in preventing Tobacco Mosaic Virus if you understand a little bit more about the disease and how it is spread.

First and most important to understand is that TMV is spread by human action only, either by handling plants or garden implements / machinery. TMV is spread almost exclusively by human contact, garden implements or machinery. This is a virus and therefore is incapable of spreading by wind or water. Normally what happens is that a human has previously handled an infected plant and then handles and other plant which has some damage (it can be very small) to it. The virus enters the wound and infects the new plant. Currently there is no proof that insects can transmit the disease from plant to plant.

A plant virus such as TMV can be considered to work in the same way as a systemic pesticide, in other words, once inside the plant it travels from cell to cell and infects all parts including roots, fruits, seeds, leaves and stems. The infection can occur at any stage of the plant’s life, this virus is very hardy against cold and heat.

Other common pests and diseases which affect tomato leaves include:

  1. Tomato Blight
  2. Tobacco Mosaic Virus
  3. Nutrient Deficiencies
  4. MAIN INDEX TOMATO PESTS AND DISEASES

COMMENTS / QUESTIONS LEFT BY OUR READERS

Date: 11 January 2017 From: Justice
QUESTION: What pathogens causes tobacco mosaic disease?

A pathogen is normally considered as a virus or bacteria. With Tobacco Mosaic Virus, it is a virus itself. It is transmitted almost exclusively by human contact from and infected plant to a new one.

 

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