In winter, the primary purpose of our tractor is weed control. That means using selective herbicides, then mowing the vineyard like a 20-acre lawn. Many people have a negative image of pesticide/herbicide use in growing winegrapes. Their mental picture probably consists of a turbocharged tractor racing through the vineyard, leaving a randomly placed cloud of chemicals in its wake. Although the turbocharged tractor sounds cool, this scenario’s far from reality. Chemicals in winegrape growing are VERY selectively applied. There are many reasons for this, the primary one being that pesticides and herbicides are really expensive. Buying and applying even the most basic of chemicals is pricey. Luckily winegrapes, unlike table grapes and most other crops, have a very high threshold for damage and therefore much less need for chemicals. After all, superficial damage of winegrapes doesn’t really matter because the grapes are just going to be crushed anyway.
Another reason to apply chemicals sparingly to winegrapes is that winemakers are, by nature, paranoid. We don’t want anything on our grapes — and therefore in our wine — that doesn’t absolutely have to be there. Even applying simple chemicals, like sulfur, is looked at suspiciously if it’s done too late in the growing season.
The final reason that we keep chemical use in our vineyards to an extreme minimum is that environmental laws are so detailed that unless there’s a major need for chemicals it simply isn’t worth the effort of the paperwork and legal compliance. As an alternative, most vineyardists practice some form of Integrated Pest Management (IPM). Thanks to the principles of IPM, we use chemicals only as a dead-last resort. We can reduce or eliminate most of our pest problems simply by changing the way we farm, and by understanding the interactions of management, the crop environment and the nature of our vineyard pests. This is a vast oversimplification of the very detailed practices of IPM, but it gives you a good general idea about the philosophy behind it.
At David Coffaro Vineyard & Winery, we’re very selective in our use of herbicides to control our cover crop. A cover crop is basically everything that grows in the vineyard except the vines. Most cover crops are intentionally planted and regulated by the vineyard manager; others consist of whatever feels like growing there. Our vineyard is very much the latter. In industry lingo we maintain a “wall-to-wall native cover.” This is a general euphemism for “there’s a party in our vineyard and everyone’s invited.” Wall-to-wall simply means there’s a solid layer of vegetation from one side of the vineyard to the other (as opposed to just between the rows). “Native” means that we don’t decide ahead of time what plant species are best for our vineyard (alfalfa is often a popular choice for those who do). Instead, we let whatever plant species happen to live in the area keep their happy homes.
Unfortunately, our free-love approach to cover crops means that weeds occasionally get out of control. One of the approaches we take when this happens is to use selective herbicides, such as Simazine and Roundup. We very rarely and selectively use Simazine, but sometimes the small amount needed for control justifies its use. It’s not a horrible, toxic-waste-like substance that’ll scar the earth for millions of years to come, but it’s not a substitute for chocolate syrup on your ice cream, either. When used correctly, Simazine is very safe and effective. Roundup, on the other hand, leans more towards a chocolate syrup substitute. Although definitely still a chemical, Roundup is as close to a safe and friendly herbicide as you’ll ever find. Between the Simazine and the Roundup, we’re easily able to manage the vegetation in our field with a great degree of effectiveness
There are many factors that go into choosing what to leave and what to cut off. In general, you want to leave a balanced number of spurs and buds on each vine. (Spurs are the stubs left over after you cut the canes from the trunk of the vines.) Instead of cutting the canes off completely, you leave a two- to three-inch stub, bearing two small buds, attached to the trunk. Next year the new canes, and the new grapes, will grow from these buds. For the 100-year-old zinfandel vines on our property, we leave six to eight two-bud spurs per vine.
One problem with this method is that every year the spurs get two to three inches longer, and over time, the trunk of the vine becomes huge. That’s why it’s important to pick the six to eight spurs that’re closest to the trunk. In addition, you want leave the thickest and healthiest spurs because they’ll produce more fruit. You also want the remaining spurs to be as evenly spread out around the vine as possible, so when next year’s canes grow, they won’t have to compete for sunlight. In addition, it’s better to have spurs that point up, not out, so they don’t grow into the vineyard rows.
If you combine these principles with other similar ideas, then speed up the decision-making process, you can reduce a full-grown grapevine with 20 to 30 canes into a well-balanced trunk with six to eight well-placed spurs within minutes. Now repeat this process for a thousand vines per acre. Honestly, it can make cleaning out the fridge seem like fun.
Check out Brendan’s “Harvest Diary — A week in the life of Crush at David Coffaro Winery” at http://www.coffaro.com.