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