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Beginner

Scientific Name
            Grapevine fanleaf Virus Nepovirus(GFLV)
            Arabis Mosaic Virus Nepovirus (ArMV)

Identification
Shoots

• shortened internodes
• zigzag growth
• multiple shoots per node

Leaves

• Infected leaves on new growth are often malformed with abnormally gathered primary veins, giving the leaf the appearance of an open fan
• Exaggerated dentition of the leaf margin
• Mosaic pattern of dark green and light yellow tissue on leaves
• Bright yellow bands or ring/line patterns along major veins
• Yellowing and flecking symptoms often disappear quickly with the onset of warmer summer temperatures

Berries

• Berry set is reduced with yield losses up to 80%
• Clusters may abort into tendrils with just two or three berries

Often Confused With:
2,4-D injury – leaves are cupped as well as distorted

Chimera- proliferation of shoots at a node or lack of pigmentation on leaves localized to a single shoot, not throughout the vine

Grapevine leafroll virus – reduced berry set but foliar symptoms differ significantly with red or yellow interveinal discolouration and bright green veins and downward rolling of leaves

Period of Activity
Fanleaf symptoms are best observed early in the growing season. Symptoms of Arabis mosaic virus are promoted by cool early summer weather and in many cases disappear with the onset of warmer weather.
           
Scouting Notes
Symptoms are best seen in June before the onset of warmer temperatures. Infected vines exhibiting yellow mosaic symptoms are easy to distinquish in a vineyard, and often occur as single infected vines in a row.

Threshold
None.

Advanced

Scientific Name
            Grapevine fanleaf Virus Nepovirus(GFLV) , Arabis Mosaic Virus Nepovirus (ArMV)

Identification
Shoots

• shortened internodes
• zigzag growth
• multiple shoots per node

Leaves

• Infected leaves on new growth are often malformed with abnormally gathered primary veins, giving the leaf the appearance of an open fan
• Exaggerated dentition of the leaf margin
• Mosaic pattern of dark green and light yellow tissue on leaves
• Bright yellow bands or ring/line patterns along major veins
• Yellowing and flecking symptoms often disappear quickly with the onset of warmer summer temperatures

Berries

• Berry set is reduced with yield losses up to 80%
• Clusters may abort into tendrils with just two or three berries

Often Confused With:
2,4-D injury – leaves are cupped as well as distorted

Chimera –proliferation of shoots at a node or lack of pigmentation on leaves localized to a single shoot, not through the veins

Grapevine leafroll virus – reduced berry set but foliar symptoms differ significantly with red or yellow interveinal discolouration and bright green veins and downward rolling of leaves

Biology
Grapevine fanleaf virus is transmitted between grapevines only by the dagger nematodes, Xiphinema index and X. italiae, which feed on the roots of grapevines and can retain the virus for several months. Dagger nematodes have not been reported in  Canadian vineyards and natural spread of this virus has not been documented here.  Long-distance spread occurs primarily by movement of propagation material from infected plants.

Sensitive varieties show progressive decline, low yields and low fruit quality. The productive life of the vineyard is shortened and winter hardiness is decreased.

Arabis mosaic virus is often found in co-infections with grapevine fanleaf virus. Symptoms are similar to those caused by Grapevine fanleaf virus but are not as severe.  Long distance spread occurs primarily by movement of propagation material from infected plants. Arabis mosaic virus is transmitted by the nematode Xiphinema diversicaudatum, which has been found in scattered locations in Canada. This virus can also infect many other herbaceous and woody hosts such as raspberry, strawberry, rhubarb, cherry, peach and plum.  Natural spread of Arabis Mosaic Virus in grapevine has not been documented in Ontario, likely due to the absence of the vector in vineyards. 

Many Arabis mosaic infections are latent and vines do not show symptoms. Symptoms can vary greatly by variety, rootstock and environment conditions.

Period of Activity
Fanleaf symptoms are best observed early in the growing season. Symptoms of Arabis mosaic virus are promoted by cool early summer weather and in many cases disappear with the onset of warmer weather.
           
Scouting Notes
In Ontario, symptoms are best seen in June before the onset of warmer temperatures. Infected vines exhibiting yellow mosaic symptoms are easy to distinquish in a vineyard, and often occur as single infected vines in a row. Symptoms may vary with virus strain, cultivar and environmental conditions. The bright yellow mosaic symptoms are relatively easy to spot in vineyards.

Threshold
None.

Management Notes
Symptoms can be easily confused among viruses, nutritional or environmental effects. The only accurate way to diagnose viruses is by tissue samples analyzed at a qualified lab.  Consultants or extension specialists can help with accurate diagnosis.

Use only vines produced from virus-tested scionwood and rootstock material obtained through a clean stock or certification program.

Remove and discard infected vines.