Language selection

Search

Grapevine Yellows: Flavescence dorée and Bois noir - Identification Guide

Background

Grapevine yellows diseases caused by phytoplasmas are found in many areas of the world where grapes are grown. Flavescence dorée (FD) and Bois noir (BN) are two grapevine yellows diseases that are considered quarantine pests in Canada because they can affect crop yields of affected grapevines. There are no human health risks associated with these pests.

BN and FD are commonly found in several European countries. The first detection of one of these pests in Canada was the confirmation of BN in British Columbia during the Canadian Food Inspection Agency's 2006 routine surveillance program.

Varietal Susceptibility

All Vitis vinifera varieties are susceptible to phytoplasmas. Some of the most important varieties such as Chardonnay, Pinot blanc, Pinot noir, Cabernet Sauvignon, Sauvignon blanc, Pinot gris and Sémillon are very sensitive, whereas Merlot appears to be relatively tolerant. Plants infected with FD and BN may recover, but symptoms may reoccur, sometimes years later. Vitis labrusca and American rootstocks develop very weak symptoms or no symptoms at all. However, if infected, they may act as phytoplasma reservoirs and facilitate disease spread.

Symptoms

Grapevine yellows diseases all produce similar symptoms and many plant parts are affected including fruit, growing points, leaves and canes. Plant growth may be stunted. Grafting is often not successful and young grafted plants often die quickly. Usually a combination of symptoms will develop on plants.

Disease Progress:

Symptoms may first appear in early summer and increase in incidence and severity until harvest. Early season symptoms can be observed on the flowers and as undeveloped flower/fruit bunches. Young shoots may have closely spaced branches and zig-zag growth (Figure 2) with some early leaf rolling. Subsequently, berries will shrivel as peduncles dry. Leaf symptoms become more pronounced as the summer progresses, followed by poor wood ripening that gives the vines a rubbery, "weeping" appearance. Symptoms on newly infected plants may be restricted to a few shoots with more of the vine becoming diseased with time.

Foliar Symptoms:
(Figure 1, 4)

Flower and Fruit Symptoms:
(Figure 5)

Cane Symptoms:
(Figure 3)

Comparison of Phytoplasmas with Other Grapevine Diseases

Leaf-roll Diseases: Phytoplasma symptoms may be confused with grapevine leaf-roll disease. Grapevine leaf-roll disease symptoms usually start on older leaves and develop up the cane. Phytoplasma diseases are often first seen nearer the top of the plant. Discoloration due to leaf-roll starts between the veins and the veins usually remain green. Also, grapevine leaf-roll disease does not affect cane ripening and fruit bunches do not shrivel.

Esca Disease: Withering of the bunches and leaf reddening may be confused with Esca disease. However in the case of Esca, the stock will collapse suddenly in July or August. Esca is caused by a complex of several fungi including Phellinus igniarius and Stereum hirsutum.

Photographs:
Dr. Michael Maixner
Federal Biological Centre for Agriculture and Forestry (BBA)
Institute for Plant Protection in Viticulture
Bernkastel-Kues, Germany

Examples of FD and BN Symptoms on Riesling

Figure 1: Foliar symptoms

Click on image for larger view
Examples of Flavescence dorée and Bois noir Symptoms on Riesling - Foliar symptoms

Figure 2: Early season short internodes

Click on image for larger view
Examples of Flavescence dorée and Bois noir Symptoms on Riesling - Early season short internodes

Figure 3: Uneven wood ripening

Click on image for larger view)
Examples of Flavescence dorée and Bois noir Symptoms on Riesling - Uneven wood ripening

Examples of FD and BN Symptoms on Pinot Noir

Figure 4: Foliar symptoms

Click on image for larger view
Examples of Flavescence dorée and Bois noir Symptoms on Pinot Noir - Foliar symptoms

Figure 5: Affected fruit

Click on image for larger view
Examples of Flavescence dorée and Bois noir Symptoms on Pinot Noir - Affected fruit

Date modified: