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Ministry of Agriculture, Food and Rural Affairs

grapevine leafroll virus

Grapevine leafroll virus on Cabernet Franc Grapevine leafroll virus Grapevine leafroll virus on Cabernet Franc Late season leafroll symptoms on a red-berried variety. Note downward leaf curl and green area around principle veins. Leafroll Virus on Chardonnay Late season leafroll on a white-berried variety. Note downward leaf curl. On some varieties, yellowing of the leaves may not be evident. Leafroll Virus on Chardonnay Late season leafroll symptoms on a white-berried variety. Note downward leaf curl. On some varieties, yellowing of the leaves may not be evident. Click to enlarge.

Beginner

Scientific Name
Grapevine leafroll-associated (CLRaV) closteroviruses

Identification
Shoots: 

  • Shorter than on healthy vines

Leaves: 

  • No visible difference between diseased and healthy vines in the spring
  • Slightly smaller than healthy vines
  • As the season progresses, diseased leaves turn reddish in red varieties or yellowish in white varieties, thicken and become more brittle
  • By late summer leaves roll downwards starting at the base of the shoots. The leaf blade may be bright yellow or red, but the main veins remains green

Fruit

  • Clusters smaller than normal but with normal-sized berries; up to 30-50% loss in yield
  • Often matures late and irregularly
  • Soluble
  • Low in sugar (25-50% reduction), soluable solids and has poor pigmentation

Often Confused With: 
Potassium deficiency – reddish-purple interveinal discolouration starting at leaf margin but without the green colouration bordering the veins; symptoms first develop on leaves at mid-shoot

Magnesium deficiency – in red varieties,  reddish interveinal discolouration starting at leaf margin but without the green colouration bordering the veins; symptoms first develop on basal leaves

Pototo leafhopper “hopper burn” – downward curling leaves but adults can be seen flying and nymphs or their cast exoskeletons can be observed on the undersides of the leaves

Period of Activity
Most visible symptoms appear in mid to late summer.

Scouting Notes
Basal leaves will exhibit symptoms in mid- to late summer.  Both red and white varieties will have downward rolled leaves.  The leaf turns red (red varieties) or yellow (white varieties) while the main veins of the leaf remain green.

If you see symptoms of grape leafroll virus, look for grape mealybug.

Threshold
None.

Advanced

Scientific Name
Grapevine leafroll-associated (CLRaV) closteroviruses

Identification
Shoots: 

  • Shorter than on healthy vines

Leaves: 

  • No visible difference between diseased and healthy vines in the spring
  • Slightly smaller than healthy vines
  • As the season progresses, diseased leaves turn reddish in red varieties or yellowish in white varieties, thicken and become more brittle
  • By late summer leaves roll downwards starting at the base of the shoots. The leaf blade may be bright yellow or red, but the main veins remains green

Fruit

  • Clusters smaller than normal but with normal-sized berries; up to 30-50% loss in yield
  • Often matures late and irregularly
  • Soluble
  • Low in sugar (25-50% reduction), soluable solids and has poor pigmentation

Often Confused With: 
Potassium deficiency – reddish-purple interveinal discolouration starting at leaf margin but without the green colouration bordering the veins; symptoms first develop on leaves at mid-shoot

Magnesium deficiency – in red varieties,  reddish interveinal discolouration starting at leaf margin but without the green colouration bordering the veins; symptoms first develop on basal leaves

Pototo leafhopper “hopper burn” – downward curling leaves but adults can be seen flying and nymphs or their cast exoskeletons can be observed on the undersides of the leaves

Biology
Leafroll affects hybrids, rootstocks and native grapes (ie. Concords) as well as vinifera varieties.

Grapevine leafroll virus is localized in the vascular tissue, (i.e. phloem) so it interferes with the movement of nutrients in the vine, thereby causing foliar symptoms of nutrient deficiency.  Infected vines are more sensitive to environmental stresses such as drought, excessive moisture, pollution or cold.

Leafroll is transmitted by grafting and persists in propagative material (budwood, rootstocks, grafted vines) which are largely responsible for its dissemination over medium and long distances.  Infected rootstocks are symptomless aside from reduced vigour so the risk of disseminating the disease is increased if untested rootstocks are used. 

Grape mealybug and soft scale are known vectors. Grape leafroll virus is not known to be seedborne. 

Period of Activity
Most visible symptoms appear in mid to late summer.

Scouting Notes
Basal leaves will exhibit symptoms in mid- to late summer.  Both red and white varieties will have downward rolled leaves.  The leaf turns red (red varieties) or yellow (white varieties) while the main veins of the leaf remain green.

If you see symptoms of grape leafroll virus, look for grape mealybug.

Threshold
None.

Management Notes

  • Use certified virus -free grapevines.
  • 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.
  • Mark and replace infected vines when possible to limit the possibility of further spread in the vineyard.
  • Natural spread is slow in commercial vineyards. Mealybugs are rare in Ontario vineyards, and do not directly affect vine performance. The control of vectors using insecticides is not recommended and has not proven to be effective for limiting the spread of viruses.