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Managing the Canopy: Preventative Maintenance in the Vineyard
NM: Speaking of vineyard management, you're a big proponent of holistic and preventative practices in vine maintenance. For example, you mentioned that you maintain a two-shoot-per-cane maximum in an effort to control canopy growth. Can you say more about that and why it's important?
RS: Going through the vineyard, we identify the two main shoots that we want to keep, which have clusters. Other shoots that are growing also have clusters, which [if they were allowed to mature] would make the crop load too big, the yield too high. So we want to thin all that out, opening up the canopy. We want an nice open area throughout the vines. Otherwise, if all the other shoots were allowed to remain, all the space would be filled in with leaf area and more shoots. In that case, we wouldn't have as much sunlight and airflow penetrating, producing a dense type of canopy that would then retain humidity coming off the ground or from the air, keeping things moist and dark, and ultimately encouraging mildew growth and harboring more insects. So, thinning out the canopy is a cultural way to reduce the pressure of disease and insects, without having to use chemicals. Plus it's also yield control, at the same time.
NM: What you're suggesting, then, is that by virtue of the choices you're making in pruning, you're preemptively reducing the need to apply pesticides later on.
RS: Yes. Specific procedures in canopy management will help you drastically reduce the need for pesticide application. It's part of an Integrated Pest Management (IPM) program. Another part of that comes later on when, after we've removed some shoots, we remove leaves around the clusters after they bloom and the berries have set. We'll remove the leaves right around the clusters that are creating this microclimate around them, encouraging mildew to form…
NM: …because of the shading and the lack of air circulation, which becomes more crucial as the berries' viability increases…
RS: …and as the canopy gets bigger, because you'll get bigger and more numerous leaves. Here's why. The secondary shoots (called lateral shoots), growing off the main shoot, will continue to grow and add leaf area. And so later on, as those lateral shoots get bigger, [unless we remove them] the vine area will close in more and get more dense with leaves. We want to remove some of leaves down low around the fruit, because the upper parts of the vine will continue to grow out and create an umbrella type of canopy over the vine itself. That allows for air circulation and also for diffuse light down near the fruit so mildew and fungus doesn't grow in there. We want a little bit of light, but not direct sunlight on the fruit. And we do that by removing the foliage closer to the fruit clusters, but leave a single layer type of umbrella over it to allow for diffuse light exposure.
NM: That's got to be a lot of work! Practically speaking, that must be very high maintenance, because you're having to go cluster-by-cluster and gauge how much of an immediate canopy it has and cut back on that, ultimately ensuring that there is still canopy up high and far enough from those clusters give provide the diffuse light and airflow you want.
RS: Yes, and there's so many different types of trellises that you'll see in the [Napa] Valley. And where we are, for what we're doing, this one works really well for us. We like the fact that we have an umbrella canopy over the fruit and can open it up inside so we have good airflow and nothing around the clusters themselves. And then, when we do apply the fungicides for mildew prevention, it's really efficient because we've got an open fruit zone that we can apply the sulfur to, and it can find its way through the vine and really cover the fruit. That allows us to be more effective with our coverage and reduce the number of times we need to apply it. It's extra work in hand labor to go through and manipulate the canopy that way, but it's very effective and reduces other needs.
NM: Beyond canopy management, how else do you manage vineyard pests?
RS: It's all part of that IPM program, which means reduced inputs, more monitoring, and higher threshold levels. Threshold levels involve determining when a pest is approaching an economic level that we need to control so we don't have a problem, such as reducing our crop or making the crop in some way not saleable or garner a lower price or make not as good a wine. We live with higher thresholds, meaning that we allow for some degree of various insects living on the vines and simply monitor them to ensure they don't exceed a certain level. Because there are other natural predators living in the vineyard that keep them in balance.