Grape Leafroll Disease

Grapes November 08, 2013|Print

Symptoms       Management Options       Causes       More info

Stephen Jordan, University of Wisconsin-Madison

Symptoms

Grape leafroll disease. Photo by Ed Hellman, Texas AgriLife Extension.

Symptoms differ depending on the variety of affected grape and are best observed in late summer and fall. On red-skinned varieties of Vitis vinifera, leaf tissue between the veins turns deep red to purple, with downward curling or cupping of the leaf margins. On white varieties, the leaf tissue will turn yellow with curling or cupping of the leaf margins. For both symptom types, the veins will remain green. Rootstock, American native, and hybrid varieties can be infected, but typically do not show symptoms. Vines with leafroll disease are less vigorous than healthy vines and may be less likely to recover from winter injury due to reduced carbohydrate stores. Leafroll affected vines can have yield losses of 30-50%, delayed and uneven ripening of fruit, a reduction in brix and berry color, and an increase in titratable acids. Phosphorus and potassium nutritional deficiencies [1] mimic many of the symptoms caused by grape leafroll disease. For this reason, confirmation of leafroll infection prior to management decision-making is recommended.

Cultural Management Options

  • Plant healthy stock. This is the primary defense against grape leafroll disease. Use planting material that is certified to be free of leafroll virus. Clones of most rootstocks and cultivars that are free of all known viruses are available. Remember that if a nursery is propagating certified virus-free stock for selling, this propagated material IS NOT certified virus-free. Only material that comes directly from a certification facility can be called "certified virus-free". Ask your nursery if their Mother Blocks have been recently tested to ensure that they are still virus-free.
  • There is no way to cure an infected vine. Remove and destroy virus-infected vines. Top-grafting is not advisable, as rootstocks may be infected.
  • Monitoring for and controlling mealybugs and soft scales are important in vineyards with confirmed grape leafroll disease.

Chemical Management Options

Currently, there is no chemical control for grape leafroll disease. Chemical control of potential insect vectors of the viruses that cause leafroll disease may help limit spread of the disease within a vineyard.

Causes

Grape leafroll disease symptoms are associated with at least ten different viruses that are referred to as Grapevine Leafroll-Associated Viruses (GLRaVs). The distinct viruses are named GLRaV-1 through GLRaV-10, based on the order of their discovery. The most common means of spreading leafroll-associated viruses is through vegetative propagation and grafting. GLRaVs can be moved across long distances in planting and propagation materials. In addition, two insect vectors, mealybugs and soft scales, have been shown to transmit GLRaVs between vines, and in some cases, between nearby vineyard blocks. Confirmation of a suspected leafroll infection can be made by a commercial or university laboratory. When submitting samples for testing, it is advisable to contact the testing facility prior to sampling to obtain proper collection, storage, and submission procedures.

Recommended Resources

Mealy Bugs and Grape Leafroll Disease, University of California

Grape Leafroll Disease, Washington State University

Major Grapevine Diseases: Fanleaf and LeafrollWashington State University

Pacific Northwest Plant Disease Management Handbook:  Grapevine Leafroll Disease, Oregon State University

Field Monitoring for Grapevine Leafroll Virus and Mealybugs in Pacific Northwest Vineyards, Oregon State University

Grapevine Leafroll Virus and Mealybug Prevention and Management in Oregon Vineyards, Oregon State University

Grape Leafroll Disease, Cornell University

Grapevine Nutrition, Oregon State University

Ringspot Virus Decline

Grape Leafroll Disease video, Washington State University

 

Reviewed by Damon Smith, Oklahoma State University and Michelle Moyer, Washington State University

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