A Fungus Among Us
It is at this time of year I am reminded of the fact that when you buy a house in an agricultural community (Napa for us) you are required to sign a document stipulating that you understand you live in such a community and any noises and scents associated with it cannot be subject to litigation. Never is this more apparent than in the spring time or as we like to call it, frost season (duhn, duhn, duuuuuhhhnn). For the noise part, we have to deal with the chopper-like sounds of the wind machines on chilly nights. The scent part is even worse- while my allergies are already in spring-driven-hyper-drive, I also have to deal with the decidedly unpleasant aroma of sulfur.
Powdery mildew is the disease caused by the fungus Uncinula necator. Right now, we are in the growth phase of the vines and new plant tissue is growing like crazy. This nice, soft, tissue is not only susceptible to frost, but also to this type of mildew. The mild daytime temperatures and higher humidity that are the hallmark of spring are great initiators for the growth of the mildew spores that have been spread by the other aspect of spring, wind. To give you an idea of how serious powdery mildew can be, it is hands down, the most widespread disease and probably the most costly in terms of crop loss in the state of California, and most likely in any winemaking state (which is all of them) in the United States. The damage incurred by the vine depends on the time of the original infection.
Early on, it can cause scarring, malformed berries, cracking, poor color development, and yield reduction. The fruit is susceptible from first growth until it reaches 12-13 brix (from then on, it becomes susceptible to Botrytis, a fungus I covered in a previous post). And once it’s in the vineyard, there is a constant battle for the remainder of the year, until winter when the spores are dormant and can be treated with a lime-sulfur application.
As usual, an ounce of prevention is worth a pound of cure- even if that prevention makes my nose itch and head ache (granted, most people don’t even know when a vineyard has been dusted, I just happened to be cursed/blessed with a very acute sense of smell). Most vineyard owners, both organic and non-organic, dust the vineyards with a sulfur/copper compound to prevent powdery mildew from taking hold. So this, along with shoot thinning and suckering, and constant vineyard monitoring and canopy management help keep the fungus from being among us.
On another note, if you have been bombarded by notifications, there was some testing being done on the website (no it was not me harassing you into reading my blog) and we are working to correct the problem!
Photos from en.wikipedia.org[jetpack_subscription_form]