Pest Alert
Agricultural Commissioner
Santa Barbara County

Cucumber Mosaic Virus

The Pathogen: Cucumber Mosaic Virus (CMV) attacks a great variety of vegetables, woody and herbaceous ornamentals, and native plants (as many as 191 host species in 40 families). Symptom expression depends upon the type of plant and plant part affected making it difficult to identify CMV from symptoms alone. The most common symptoms are mild to severe mosaic or mottling of leaves or flowers, and stunting or yellowing of entire plants. Additional symptoms include flecking, dwarfing, and fern leaf.

CMV in Guinea gold vine (Hibbertia sp.) Plants show yellowing and mosaic patterns on foliage  
  CMV in Mandevilla sp. Plants show yellowing and mosaic patterns, often including rings.

 

 
CMV in ornamental potato vine (Solanum jasminoides). Leaves show distinct mottling and malformation.  

Distribution and Diagnosis: CMV is distributed worldwide and very common in temperate regions.
The presence of the virus can be confirmed by laboratory tests.

Pathogenesis: CMV produces a systemic infection in plants. Plants cannot “outgrow” CMV. Once infected, they harbor the virus for their lifetime. The virus does not usually cause symptoms in older tissues that developed prior to infection. The severity of symptoms in younger tissues that develop after infection is variable between host plants.

Transmission and Spread: CMV overwinters in many weeds, flowers and crop plants. CMV is primarily transmitted by aphids (more than 60 different species) and can be acquired in only 5-10 seconds of feeding. Weeds harbor the virus and aphid populations in the absence of susceptible hosts. The virus can also be transmitted through seeds or bulbs in some plant species. Once a few plants have become infected with CMV, insects and humans (during cultivating and handling the plants), readily spread the virus to healthy plants.

DISEASE MANAGEMENT

There are no chemicals that will cure a plant of this or any virus. Immediate roguing of infected plants is the only way to stop the spread of cucumber mosaic virus.

Prevention: Due to CMV's broad host range and potential for damage, testing is commonly incorporated into indexing and viral screening programs. CMV can easily be moved from one plant to another by just sap on a hand or cutting knife. For this reason it is extremely important to prevent the movement of sap between plants.

All stock coming into the nursery should be virus-free (at least by visual inspection). If there is any question, material should be held in a separate “quarantine” area of the nursery until determined to be clean. Because CMV can be seed transmitted to some hosts, it is important that seed be certified by the producer to be free of all viruses as well as other pathogens. Some producers provide propagative stock material that it is “certified virus-free”.

Cultural Control: There are some CMV-resistant varieties of vegetables and flowers available; however, there are many ornamental hosts that do not have resistant cultivars. Symptomatic plants should be rogued immediately. Perennial weeds should be eradicated from around greenhouses, gardens and fields to eliminate possible sources of CMV and aphids.

Chemical Control: There are no chemicals that can eradicate viruses from an infected plant. The widespread continuous use of insecticides to control aphid populations in nurseries is neither realistic nor practical. Spot treatments for aphids may be effective when populations reach high levels. Removal of weeds that support high aphid populations in addition to harboring CMV is very important

Ornamental Hosts of Cucumber Mosaic Virus Reported in California
Snapdragons Antirrhinum majus   Iris Iris sp.
Columbine Aquilegia sp.   Lily Lilium sp.
Potato Vine Solanum jasminoides   Mandevilla Mandevilla sp
Butterfly Bush Buddleia davidii   Heavenly bamboo Nandina sp.
Saffron Flower Carthamus sp. Nasturtium Nasturium sp.
Dichondra Dichondra repens   Passion vine Passiflora sp.
Geranium Pelargonium sp.   Begonia Begonia sp.
Gladiolus Gladiolus X hortulanus   Gold Guinea Vine Hibbertia sp.
Sunflower Helianthus annuus   Viburnum Viburnum sp.
Houttuynia Houttuynia cordata   Periwinkle Vinca sp.
Snail Vine Vigna unquiculata   Freesia Freesia sp.

This list is complete as of January 2000. New ornamental hosts for CMV are described every year.

Santa Barbara County
Agricultural Commissioner's Office
263 Camino del Remedio
Santa Barbara CA 93110
(805)681-5600
February 16, 2000