Wijngaarden rooien. Dat lukt de meeste wijn boeren nog wel. Maar de plant met wortel en tak uitroeien is een andere zaak. Wortels of restanten daarvan kunnen doorwoekeren. Met vaak als gevolg dat zich in tot zwijgen gebrachte wingerds ondergronds allerlei nieuwe ziekten en parasieten kunnen ontwikkelen. Mocht zo’n wijngaard zijn gerooid om hem te herbeplanten met andere druivenrassen, dan kan dat weggegooid geld blijken wanneer ondergronds de vernietiging toeslaat. Daarom wordt hard gestudeerd op doeltreffende opschoningsmethoden van druivenakkers. Er zijn al allerlei experimenten gaande. Maar hoe simpel het planten van een wijnstok ook mag zijn, hij is bijna niet kapot te krijgen. Soms bot het restant na jaren weer uit. Lees op Wines @ Vines hoe Amerikaans experts hierop hun tanden stuk bijten.

“Considering how much cash and work growers spend to keep grapevines healthy, they are surprisingly hard to kill. It’s easy to rip vines out or cut them down, but that doesn’t usually kill them. Living remnants of the roots will remain, hosting pathogens and pests that could threaten future plantings. Responding to the need to replace individual defective vines, replant whole vineyards that have declined, are unpopular varieties or have disease issues, Dr. Brad Hanson, a weed science specialist at the University of California, Davis, discussed how to kill vine roots for pest and pathogen management and re-development at a recent meeting of the Napa Viticultural Technology Group. Encouraged by Napa County UCCE farm advisors Monica Cooper and John Roncoroni, Hanson conducted a number of trials. He first noted that vines that appear dead can sprout, citing an example that UC Davis’ Andy Walker found after eight years of dormancy. “If the roots continue respiration, they can continue to host pathogens and parasites,” Hanson said. Can you kill all the roots of individuals vines infected with leafroll virus to minimize the spread by mealy bugs and other vectors? To find out, Cooper and Roncorni tried various combinations of cutting off trunks, drilling holes, injecting or slashing with a hatchet followed by painting with glyphosate (Roundup), triclopyr (Garlon and Release)—although technically not registered for use on grapevines, they are on trees—or water. They tried the EZ-ject, a device that uses an internal hammer to “shoot” insecticide into a vine. At a test plot, the grower had also tried drilling a large hole and filling it with 2 ounces of herbicide. That method didn’t work well: Most of the live tissue lies close to the outside, under the bark. Some treatments are somewhat effective, but they’re mostly ineffective and inefficient. “Two-thirds of the roots were still alive with our best effort,” Hanson commented. At best, almost 35% of the vine roots were killed; just cutting the vines left almost 90% alive. In a second phase of research, Hanson, who specializes in killing weeds, tried chemical treatments to kill a whole vineyard as part of a planned replanting effort to deprive pests and pathogens a host and food source during renovation.”