As the growing season kicks in, two things happen in stark juxtaposition: The days get gloomy, and at times balmy. At the same time, one of my favorite trees, the Jacaranda, comes into bloom in vibrant light purple flowers.
Unfortunately, this is no time to revel in my oasis of bucolic bliss (not that I could, because one slight turn of the head and I see the bustling freeway…).
Evil is afoot: Powdery Mildew’s insidious and often rapid advance, requires vigilance and quick action.
Powdery hit my Aglianico hard in 2010 and 2011. The Montepulciano seemed more resilient. Until this year….
So on my birthday, I left my baby son with my parents, mixed up some sulfur, filled up the backpack sprayer and huffed up the hill to fight the year’s first battle with PM.
This is not a difficult task, but it gets messy and does leave a lingering stink on clothing and skin.
I use Bonide elemental sulfur with an agricultural surfactant. It takes two trips with my 4-gallon backpack sprayer to cover the 10 rows of wines.
You get what you pay for. My sprayer works fine, but when I have it filled to capacity, the solution overflows through the top and runs down my back.
It really does not smell too bad until I get in the shower. The clothing worn for the task needs a few cycles in the washer and a day out on the clothesline. But it must be done. An infected vineyard can take a big hit to its crop.
(A similar capacity sprayer would cost close to $100 at a hardware supply retailer, instead of the $40 I paid for mine on eBay. I have learned to stick to my budget. I’m not looking to make a small fortune, but I don’t want to sink one into this project, either).
I’ll be brief in discussing PM here and refer to the full online resource.
Powdery mildew and its spread are driven by heat and not so much moisture. For every day the temperature stays above 70°F, the disease pressure goes up. And the mold spreads. Of course, moisture and humidity are a factor, but second to the heat. June Gloom, then is like jet fuel for PM in Southern California.
The UC Davis site, linked above, provides some useful tools to calculating the PMI (Powdery Mildew Index) and offers some interventions as well as a helpful spray schedule. I have not started to calculate the PMI and have been going by what I seen in the vines. because I still need to get an updated weather station in the vineyard.
My next post will detail the extent of damage PM can inflict. It will illustrate why I will be lugging that tank up the hill more often.
Ultimately, though, I cannot spray more often than once a week – event when there is a full-blown epidemic. When temperatures exceed 85°F, caution is advised so as to not burn the vines. While not a fatal injury, it is to be avoided. My approach has been to pick a day when two or more subsequent days are forecast to be under 85°F, and spray in the afternoon – around 4 or 5 pm. This buys some extra time without excessive heat.
June 8, 2012:
I have uploaded a video illustrating one thing that can help improve canopy ventilation: