Virus diseases of carnations
Note Number: AG0174
Jane Moran, Knoxfield
Updated: September 1994
Carnations are affected by over 15 virus diseases, but not all of them have been reported in Australia. Five of these are important in Australian carnation crops.
Carnation mottle virus (CarMV)
CarMV is the most common and widespread virus disease of carnations. Most carnation cultivars infected with this virus do not express symptoms. In other cases, when the symptom is expressed, the infected plant may have a yellow mottle on the leaves. Flower quality and yield are reduced. "Virus free" plants have broader leaves and more vigorous growth. CarMV is highly infectious and is rapidly spread from plant to plant by foliage contact or during handling. Research has shown that up to 75% of carnations initially free of CarMV became infected within six months when grown in the same glasshouse as carnations infected with CarMV.
Carnation vein mottle virus (CVMV)
CVMV causes yellow spotting and mottle patterns on the leaves of infected carnations. Young leaves tend to exhibit spots and flecks of a darker green colour on the veins. Infected plants have depressed yields and the incidence of "colour breaks" and calyx splitting are greater. CVMV is spread from plant to plant by aphids and is found wherever carnations are grown.
Carnation etched ring virus (CERV)
In certain cultivars CERV causes brown flecks, rings and line patterns on the leaves (see the picture). Sometimes infection by CERV is mixed with infection by CarMV. This causes more severe symptoms such as leaf yellowing, brown spots and rings on leaves, and streaking and flecking of the stems. Plants infected by CERV have been shown to flower at a later date and the flower quality is reduced. CERV is spread from plant to plant by aphids.
Carnation latent virus (CLV)
CLV causes no distinct symptoms on carnation plants; however, it can affect crop production and has been demonstrated to impair flower quality. It is transmitted from plant to plant by aphids.
Carnation necrotic fleck virus (CNFV)
CNFV can cause considerable damage in carnation crops. Symptoms include yellow or brown flecks and streaks on the leaves, sometimes followed by reddening and necrosis. Flower quality and yield are affected.
Crop losses attributed to virus infections
A study that was conducted over a two-year period in England and in which the yield of a "virus-tested' carnation crop was compared to that of a virus infected crop, indicated that the yield was 39% greater and the profit was 20% greater in the case of the virus-tested carnations. Also the virus-tested carnations were of a superior quality.
Since there are no chemical sprays for virus control once a plant is infected with a virus there is little the flower grower can do. The only current method for controlling virus diseases is through the use of virus tested material in conjunction with strict hygienic practices. To prevent infection of this virus-tested material, the carnation grower should enforce hygiene regulations (for example, washing hands with hot soapy water before handling plants, aphid-proof glasshouses, sterilisation of cutting and propagating instruments etc). It is essential to educate staff about the spread of virus diseases.
For effective pest and disease control, correct diagnosis is essential. A commercial diagnostic service is available at the Institute for Horticultural Development. For further information, contact the Diagnostic Service. ph: (03) 9210-9222 or fax (03) 9800 3521.
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