Cucumber mosaic virus (CMV) was named for one of the first plants in which it was found. However, it can infect a very large number of different woody and herbaceous plant species.

CMV is made up of nucleic acid (ribonucleic acid, RNA) surrounded by a protein coat. Once inside the plant cell, the protein coat falls away and the nucleic acid portion directs the plant cell to produce more virus nucleic acid and virus protein, disrupting the normal activity of the cell. CMV can multiply only inside a living cell and quickly dies if outside a cell or if the cell dies.

CMV may be spread from infected plants to healthy plants…

• mechanically on workers' hands or on tools
• by aphid feeding
• through dodder
• through grafting

Vegetative propagation perpetuates CMV. Cuttings taken from an infected plant usually are infected even if no symptoms are immediately exhibited by the cutting. The virus particles are found in all parts of the plant except the few cells at the tips of the growing points.

Symptoms vary with the species of plant infected and the environmental conditions. In some cases, certain environmental conditions bring out symptoms while other conditions mask or hide symptoms. Symptoms associated with CMV infections:

• stunting
• mosaic pattern of light and dark green (or yellow and green) on the leaves.
• malformation of leaves or growing points
• yellow streaking of leaves (especially monocots)
• yellow spotting on leaves
• ring-spots or line patterns on leaves or fruit
• flower color breaking
• distinct yellowing only of veins

Some of the above symptoms can also be caused by high temperature, insect feeding, growth regulators, herbicides, mineral deficiencies, and mineral excesses. Virus diseases cannot be diagnosed on the basis of symptoms alone.

Management

There are no chemicals that cure a CMV-infected plant, nor any that protect plants from becoming infected.

• Purchase virus-free plants.
• Maintain strict aphid control.
• Remove all weeds since these may harbor both CMV and aphids.
• Immediately set aside plants with the above symptoms and obtain a diagnosis.
• Discard virus infected plants.
• Disinfest tools used for vegetative propagation frequently.
• Propagate plants via seed rather than vegetatively.