Cucumber mosaic virus

Cucumber mosaic virus (CMV) is a plant pathogenic virus in the family Bromoviridae. This virus has a worldwide distribution and a very wide host range. In fact it has the reputation of having the widest host range of any known plant virus (191 hosts in 40 families). It can be transmitted from plant to plant both mechanically by sap and by aphids in a stylet-borne fashion. It can also be transmitted in seeds and by some parasitic weeds.

Symptoms
CMV shows symptoms on leaves known as the "Shoestring" effect for most host species. This effect causes young leaves to appear narrow and the entire plant to be stunted.

Celery
CMV can cause streaking and spotting and can be often confused with symptoms of the celery mosaic virus.

Cucumber
CMV can cause cucumbers to turn pale and bumpy. The leaves of these plants turn mosaic and their rugosity is often changed, making leaves wrinkled and misshapened. Growth of these plants is usually stunted and produces few flowers. Often cucumber fruits are oddly shaped and appear gray. This appearance often leads to cucumbers being referred to as "white pickles". Often infected cucumbers are bitter.

Lettuce
CMV symptoms in lettuce can be similar to those of lettuce mosaic virus. Infected plants show symptoms of chlorosis, stunting and often do not properly head.

Sweet pepper & Chilli
CMV in peppers causes slightly different symptoms than previously mentioned. Pepper plants often have severe foliar damage, shown as mosaic and necrotic rings. Often the peppers themselves are misshapen and contain chlorotic rings and spots.

Tomato
Tomato plants are usually stunted and have poorly shaped leaves, or "fernleaf", when infected by CMV. Also certain strains of CMV can cause partial or total loss.

Chemical Control
No chemicals can cure a plant of this virus infection or of any other. The use of chemicals and insecticides to control the aphid vector is not a practical or efficient way to control the disease spread. The use of insecticides is not very successful because the aphids become irritated and therefore jump from plant to plant in an attempt to avoid the insecticides, subsequently infecting healthy plants because the acquisition and inoculation time is very short.

Cultural Control
There is no perfect control for this virus. However, removing weeds and diseased plants from fields can reduce the chance of infections. Maintaining clean and sanitized tools, machines and hands can help.

The use of resistant varieties is another way to control virus spread. Use of a resistant "trap crop" around the perimeter of a field with susceptible plants in the middle will cause aphids carrying disease to first land on the resistant varieties and by the time they have eaten their way to the susceptible varieties they will no longer be carrying the virus.

Also spraying mineral oil on plants will reduce aphid populations as the aphids do not like the mineral oil.

When planting in the same fields in successive years do not plant varieties of plants that are susceptible to CMV. Since CMV can overwinter in perennial plants and weeds the virus can enter the roots and present itself at the top of the plant in the springtime where it can be retransmitted by aphids.