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Tomato Diseases | Cucumber Mosaic Virus

Cucumber Mosaic Virus

Descriptions of Plant Viruses Website provides extensive information about viruses, viroids, and more including descriptions, taxonomic notes, and sequence analyses.


Symptoms on tomatoes vary greatly with host variety, viral strain, time of infection, light intensity, and other environmental conditions.  The most characteristic viral symptom is the light and dark green mosaic patterns on the foliage.  There may also be yellow spotting or streaking on the leaves and interveinal chlorosis, meaning there is a distinct yellowing in the veins of the leaves.  The leaves may also become twisted and curl downward and exhibit “shoestringing” of “filiformity,” in which there is a reduction of leaf blade area along the main vein of the leaf.  When shoestringing is severe, the leaves resemble rat-tails.  When an immature fruit is infected, it may develop internal browning caused by a collapse in cells.  Overall, diseased plants are stunted, have slowed growth, and produce small quantities of fruit with necrosis and delayed maturity.

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CMV symptoms on lettuce (left), jalapeño pepper (center), and pepper (right).


There are no signs visible to the naked eye.  However, under very high magnification (electron microscopy), infected tissues will reveal three-dimensional icosahedral virus particles.

Often Confused With

  • Tobacco (Tomato) mosaic virus causes mottling and mosaic, necrosis, stunting, leaf curling, and yellowing of plant tissues and can also cause deformed fruits, uneven fruit coloring, and delayed fruit ripening.
  • Herbicides such as 2,4-D cause leaf deformation resembling symptoms caused by Cucumber mosaic virus on tomato plants.

Indicator Plant Bioassay

Since Cucumber mosaic virus has such a wide host range and can be mechanically transmitted through sap, there are many available indicator plants described for testing CMV infection.  Symptoms on indicator plants are described thoroughly in Kim et. al. 2011 (pdf) and Zitikaite et. al. 2011 (pdf).

Rapid Diagnostic Tests

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Image of a positive CMV ImmunoStrip™ Test from Agdia®.