WINETECH Technical Yearbook 2020

the Okanagan Valley were not familiar with trunk diseases until very recently (last 10 years). Although wine production in the Okanagan dates back to the 1850s, prohibition in Canada wiped out many of the Okanagan’s earliest wineries and the commercial wine industry in the area was not revived until the 1930s. From this time through the mid-1970s, the Okanagan wine industry was based entirely on the produc- tion of fruit wines (berries, apples, cherries and even table grapes) and those produced from hybrid grapes. It was only in the late 1980s, when Canada entered into the North American Free Trade Agreement and opened up Canadian markets to American wine imports, that competition from im- ported wines spurred the Canadian govern- ment to implement a vine pulling scheme with grants for growers who uprooted their hybrid and Vitis labrusca vines and replaced them with Vitis vinifera. Due to the lack of trunk disease knowledge and failure to prepare for replanting strategies, most Okanagan producers are forced to follow a cut and retrain approach (i.e. vine reconstruction) (photo 6). By doing this, producers are able to gradually re-work vineyards, spread their short-term losses and relatively quickly (within two to three years) stabilise production in order for them to organise re-planting strategies. Reconstructed vineyards usually provide an extension to the productive lifespan of vineyards, but usually only for a limited

PHOTO 5. Brown discoloured xylem tissue due to trunk diseases present at the base of the trunk.

PHOTO 6. A 25-year-old Chardonnay vineyard that was retrained after remedial pruning.

0.2% of plants in a survey showed foliar symptoms) and Eutypa dieback (rarely seen). Cross-sections through arms and trunks of diseased vines showed internal brown necrosis (in a central position or v-shaped) (photo 2) together with black vascular occlusions. The most common pathogens isolated from such plants in- clude members of the Diatrypaceae (in- cluding Eutypa lata and several other species associated with Eutypa dieback or

(photo 3) and an estate located high on top of the Hawthorne Mountain in Okanagan Falls (photo 4), one of the highest elevat- ed vineyards in the Okanagan. Again, the external symptoms were dominated by stunted shoot growth and cross-sections through arms and trunks of diseased vines showed internal brown necrosis (photo 5), black-brown vascular occlusions and prominent cankers running down the trunk from large pruning wounds. Farmers in

“tandpyn”), Botryosphaeriaceae (associ- ated with Bot dieback and canker), Dia- porthaceae (mainly Diaporthe ampelina , associated with Phomopsis cane and leaf spot and Phomopsis dieback), Phaeoac- remonium minimum and Phaeomoniella chlamydospora (Petri disease and esca). Black foot pathogens are also common in the area. The second field trip (full day) to South Okanagan Valley included visits to Blue Mountain Okanagan Falls Region

WINETECH TECHNICAL YEARBOOK 2020 46