Tomato mosaic virus
The most troublesome viral disease of tomatoes
What is it?
ToMV is the most troublesome viral disease of tomatoes, causing distortion of leaves and fruit, and stunting of growth. Like PepMV it is extremely infectious, often affecting the entire greenhouse if left undetected. Early detection and confirmation of symptoms is again essential in reducing the risk of disease spread.
What does it look like?
Symptoms are likely to be first seen in early spring. They vary greatly, and are influenced by factors such as tomato variety, age and environmental conditions. Common leaf symptoms include a yellowish or pale green mosaic, sometimes with leaf curling or distortion. Occasionally the leaves can become very strap-like and distorted, similar to the symptoms produced by a hormone weedkiller. There is also an ‘aucuba’ strain of the virus, causing a bright yellow mottle with angular yellow blotches. The fruit can fail to set, or develop a bronzed, patchy appearance and/or pits or slightly raised brown spots.
How is it spread?
Infected seed, or root debris from a previous infected crop, is usually the primary source of the virus. Once within a crop, the disease is easily spread on hands, tools and clothes during handling and trimming of plants. This is the same for both indoor and outdoor plants.
How can I control it?
ToMV can be controlled by good hygiene, including disinfection of tools and regular hand washing. Inspection of bought in plants and regular monitoring is important. Infected plants should be removed and destroyed to reduce the risk disease spread (ensure that as much of the root system as possible is also removed). A good end of season clean-up (including washing down and disinfecting the greenhouse and plant supports) will reduce the risk of carry-over of this and many other pests and diseases. Some tomato varieties have resistance to some strains of ToMV, e.g. ‘Cherry Wonder’, ‘Cumulus’, ‘Dombito’, ‘Dona’, ‘Estrella’, ‘Ida’, ‘Nimbus’, ‘Piranto’, ‘Shirley’ and ‘Sonatine’.
When do I test?
Symptoms of ToMV are likely to be first observed in March/April. Testing should be carried out as soon as symptoms are detected and monitoring for symptoms should continue until the end of cropping.
What do I test?
Where possible, select areas of leaf or fruit that shows symptoms of disease. When testing fruit, select skin from an affected area and remove as much flesh as possible. For best results do not use completely dead plant material. As a general guide, use samples of leaf material approximately 25mm x 25mm.