Why do vignerons apply chemicals to manage weeds?
Perhaps to improve machine accessibility in the vineyard? It is easier to walk through if the grass is short. Pest management is aided by removing the protection of taller grasses. Aesthetics is a huge reason. No, seriously (doesn’t Vouvray look beautiful?). The majority of grape growers are applying petrochemicals to their soil (and ecosystem) to keep the vineyard looking more like croquet lawn than an explosion of knotty grass.
Mowing the mid-row alone is a possible alternative. Mulching under the vines helps keep the weeds down (just like Hill of Grace above). Yet physically cutting back weeds does not have the long lasting effect that poison does. Plus, it requires more machine passes throughout the growing season which has a high labour cost and can cause compaction issues in the soil. Alternatively, vineyards can run sheep during the winter to keep weeds down rather than apply poison to the soil. Even Casella, in Yenda N.S.W., manage their largest vineyards with rotations of grazing sheep.
Tilling the soil is also machine intensive. Most farmers will turn their soil at least once during the year. In fact, most vineyards in Sonoma County have turned their winter grass into the earth in the last few weeks. Why not leave the grass grow naturally during winter and turn it in Spring like Quivira (above) has? Poisoning the under-vine growth during winter seems a waste if the soil will be turned a few months later.
The herbicide manufactures (and the growers who use them) will insist that they are safe to use and have a short half life. I do not believe a chemical that can cause the death of one living thing will never have an unintended toxic effect on other plants, insects, water sources, animals or people. The potential longterm harm is not worth the perceived short term gain.
There is a pure beauty found in the chaos of vineyards coexisting with local weeds and grasses. It may be more labour intensive to harvest a vineyard buried in undergrowth, but not impossible.
Some chemical uses in the vineyard is necessary with regard to regional pressures, but is applying poison for weed management one of them? I merely wish that there be only prickly burrs and no irritating chemicals for those who brave entering organised rows of vines or live within their watershed.