Reestablishing a vineyard
Challenges usually include diseases.
When planting or replanting a site with vines, disease and site contamination are often the two biggest challenges that growers must mitigate, said Dr. Wade Wolfe, consultant and owner of Thurston Wolfe Winery, Prosser, Washington.
“Essentially all of the old vineyards have some level of disease contamination,” Wolfe said, adding that growers should test vines for leafroll and other viruses to determine vine health status before deciding if everything (vines, trellis, and irrigation system) should be removed or just the vines, leaving the trellis and irrigation system in place.
Site contamination issues include:
Nematodes—Several species of nematodes are found in Washington. Nematodes are common problems in the light, sandy soils of eastern Washington. Vineyard soil samples should be tested for nematodes before planting or replanting.
Phylloxera—Areas with heavier soils may have problems with phylloxera, a tiny louse that feeds on vine roots. Potential problem areas are western Washington, some areas of Walla Walla, and Oregon’s Willamette Valley. Phylloxera has been found in Washington on old Concord vineyards, though not in wine grape vineyards.
Soil-borne fungal diseases—These are usually not a concern, although he has seen some problems with verticillium wilt where grapes followed potato crops.
Weeds—Noxious weeds that cause problems are field bindweed, Canadian thistle, and Bermuda grass. He recommended eradicating noxious weeds before planting the vineyard.
Residual herbicides—Know the cropping history of the ground, especially if it was planted to something beside grapes. Was simazine heavily used? Wolfe has seen Merlot vines struggle to become established in land that was extensively farmed in mint.
Heavy metals—Heavy metals, such as arsenic, were used as pesticides years ago in apple and pear orchards and can affect establishment of new vineyards, though this is rare.
Vertebrates—Old vineyards are often heavily infested with gophers, sage rats, and other rodents, which should be eradicated before planting young vines.
To treat weeds and nematodes, he suggested soil fumigation or leaving the ground fallow for one to two years and growing brassica as green manure to add soil tilth and reduce nematode populations. The only treatment he’s aware of for residual herbicides in the soil is adding activated charcoal to the soil.
The condition of the soil should also be considered when deciding if vines only or the entire vineyard will be removed. If extensive soil work and amendments are needed, it’s more effective to start with a clean slate and remove everything.
In Wolfe’s viticulture consulting work, the number-one problem he sees in existing vineyards is soil compaction and/or caliche. “If the vineyard wasn’t cross-ripped originally, the ground will probably need cross-ripping now that it’s older, a chore that is done more easily with the existing trellis and irrigation system removed.”
Another common ailment he sees in older vineyards that have been drip irrigated for many years is accumulation of salts and sodium in the soil, both of which can impede water penetration and affect the growth of vines. And if the drip system is 20 years old or more, the emitters are likely plugged or semiplugged and should be replaced. Treatment for salt accumulation includes banding sulfuric acid along the vine row or adding sulfur. Calcium or magnesium will also displace sodium, and sprinkler irrigation can drive the salts from the root zone.
Soil nutrient excesses are rare, he said, though he has seen high nitrogen levels where hops were grown for many years before grapes. Soil samples will indicate if nutrients need to be added before vines are replanted.
“If you need to do extreme soil amendment work, or need to do ripping or fumigation, it’s preferable to remove the trellis and irrigation systems,” he said during the vineyard reestablishment session.
In a replant situation, growers may want to change the row orientation from the old vineyard. “Our row orientation ideas have changed from when we planted everything in a north-south orientation,” he said. Depending on your block and slope, a southwest by northeast slant may be more favorable.