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Powdery Mildew Control, without Chemical Fungicides. What's a Vintner to Do?

In my last post, I gave the Round Up run-down. What about chemical fungicides? Yeah, so, not looking so hot there either. Agricultural fungicides are decimating bee populations (and bees pollinate many important crops, so you see where this ends), they mess with mice neurologically and are "bad news for neurons" (suggesting further human study might be in order), they reduce soil microbiological diversity, and they are highly prone to developing fungal resistance. And they show up in your wine.


So we don't use them either. And it's all good. It's taken us a few years, but we've managed finally to lock down really good mildew control in the vineyard using a simple philosophy: No Tyvek.


Worker in Tyvek. Umm, no thanks.

If you have to wear hazmat protection when you spray it, we don't do it.


We are at high risk for fungal infestations in the vineyards here on Vancouver Island, and that's been made a bit worse historically by the clonal selections planted early on. We love Ortega as a varietal especially, like so many people on the island, but it makes fighting mildew on your roses look like child's play. We inherited about a dozen rows of Ortega, and those rows made great wine (especially sparkling wine), but they are a lot of work. But we're doing it.


What was the trick in the end? The first thing was getting our soil healthy. When we bought the estate, the land had been treated with chemical herbicides, chemical fertilizers, and chemical fungicides, as part of what is actually a completely conventional approach to vineyard management.


We get it: we are definitely the happy outliers here.


The trouble is, even chemical fertilizers (made of inorganic salts) are a negative feedback loop (for earthworms, the water, the air), and we didn't want to go that route. We wanted to think that someday, when we kick the bucket (as we suppose, in time, we all must), we left this piece of the earth better than when we found it.


So we went cold turkey on the chemical stuff. We brought in the chickens, ducks, geese, and sheep. We rounded up sustainable sources of seaweed, saved our oyster shells, and found local wood chips, we started making biochar in pits (with some comic early failures), brewed compost teas, raised worms in garbage pails, shoveled manure, and stopping tilling. By the third spring, the soil was teeming with organic microbial life, and the effects were beneficial. The plants were healthier and had a better nature resistance. The soil was healthier and also supporting disease resistance.


That left us in a good position to use gentler methods to help the vineyard along. After all, we do need to control for mildew, or we won't have any grapes at harvest. So our second focus was on finding good tools that are organic-certified and were aimed at making our grapevines less attractive hosts for fungal populations rather than eradication.


We start in the spring with a horticultural oil, sulfur, and hydrated lime spray routine, while the vines are still dormant. We experimented with different oils, but we like the basic recipe developed by Cornell University (with some important tweaks): Neem oil, baking soda, and a splash of Dr. Bronner's Castile soap. This horticultural oil is also great on the fruit trees in our heritage orchard and on the roses we use in our perfume production. If you want the recipe, come visit us, and we also sell the Parsell horticultural spray concoction, tweaks and all, in the tasting room (or email us if you can't get out) if you want to try it in your garden.


From there, we don't have to worry too much about mildew until the leaves are out on the vines and the weather starts to get warm and wet. That's a good thing, because the spring is a crazy time in the vineyard with other tasks and projects.


Warm and wet are just what you'd like most if you were fungus, and when that comes we have to spring into action. We're relatively lucky here, because our location is just over a mile from the sea, and, with the way the winds run in the summer, we often get a cool breeze off the ocean in the late afternoons. That means canopy management is a big deal for us: if the breeze can get through the vines, it will dry out the leaves and help protect against mildew. We let the sheep munch in the vineyard before the grapes get sugary and change color (and under a careful eye, because they will eat just about anything). They help out by eating some of the lowest hanging leaves. The rest, we pull ourselves by hand in June and into July, trying to give the grapes enough shade that they don't get sunburned (it's a real thing) but enough room inside the canopy that the air can flow. We also keep a careful eye on irrigation during the peak danger zones. Adding water to the equation is not helpful.


We wish we could do it all with canopy management and plant health, but by May or so we generally have to start with a weekly preventative spraying program. The goal here is to make the environment on the grapevines less hospitable to spores, largely through changing the pH of the canopy and knocking the spores about a bit. It's an entirely preventative program, which means we are very, very vigilant.


We spray early in the day with a concoction that includes a bit of Neem oil (a natural fungicide), a bit of Castile soap (a "sticker" that helps the spray adhere to the leaves and which also smothers aphids), a mix of sodium bicarbonate (baking soda), potassium bicarbonate (baking soda's cousin), and a bit of our own vinegar (all acidifiers), a nettle, horsetail, and comfrey tea (natural fungicides), and sulfur (natural fungicide) until about the first of August. (After that, using sulfur will create problems with fermentations in the winery, so we have a 30+ day cooling-off period on sulfur before harvest). We do use at the end of the season one organic-certified commercial product, Serenade, which is a patented strain of the Bacillus subtilis bacteria that counter-acts mildew pressure and does not harm pollinators or beneficial insects.


We also spray with milk, believe it or not. There is some good evidence to show that milk is a great natural fungicide. At the moment, we're using organic powdered milk, since we can't justify using fresh milk in the vineyard as a food-security issue. We'd rather be using island-sourced whey for those trials. The enzymes in fresh, non-pasteurized milk are meant to have an additional beneficial action, and whey is a food production by-product generally discarded.


So if anyone on southern Vancouver Island knows a source for raw whey, let us know!


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