Passive Frost Protection

I had a great email conversation with our county viticultural advisor, Rhonda Smith, this week about passive frost protection. She is a co-author on a narrated slide presentation called “Passive Frost Protection“. The University of California Cooperative Extension also has several other slide shows on Active Frost Protection, but I was more interested in the passive methods as we live in the Dry Creek Valley “banana belt” and have never used active frost protection methods.

Due to the frost losses that we, along with so many others, experienced in 2008 due to freaky La Nina related Spring frosts, I thought I would revisit this topic as we are in another La Nina weather pattern.

The most intriguing aspect of freezing events is the way air flows from higher to lower areas just like a stream of water. This river of air will flow down hills into valleys, moving around slightly higher valley floor areas, pooling in lower valley floor basins and stopping if impeded by a row of trees, a raised berm, levee or fence. (Image courtesy of Mercy Olmstead, PhD, University of Florida-IFAS)

So, what can one do passively to decrease the chance of freezing injury?

1) Mow the cover crop as low as possible to allow sunlight to reach the ground and warm it during the day. That warmth will be released back into the air at night.

2) Provide as much undisturbed bare earth around the vines as possible. Do not cultivate or disc just before a potential frost. If cultivation is needed follow the disc with a roller then wet thoroughly. No sprinkler system? Then do this when rain is forecast so that the large air spaces that are formed during cultivation are reduced. No compaction (large air spaces) or dry soil decreases the ability of the soil to hold the warmth of the sun.

3) The most interesting thing that I learned this Spring is that 99% of ice nucleation between 23-32F is, in fact, facilitated by bacteria! One could possibly reduce the population of ice-nucleating bacteria before a freeze and reduce the formation of frost and accompanying frost damage by using copper or zinc. It is also possible to introduce a non-ice-nucleating bacteria to out compete the ice-nucleating bacteria. Cover crops are often reservoirs of ice-nucleating bacteria so mowing the cover crop and reducing the vegetation can be helpful.

I will update this blog entry as we move through April to see how our passive frost efforts work!

Timeline:

Week of April 3-9 – Possible cold weather forecasted for the end of the week so all cover crops are mown. Chard, Petite sirah and Petit verdot given their first fungicide application that includes the micronutrient zinc on Friday, the day before a significant frost is forecast.

Week of April 10-16 – a few days in the high 30’s but no frost here!

Week of April 17-23 – no frost forecast due to unsettled, cloudy weather.

By | 2017-05-19T21:03:38+00:00 April 9th, 2011|Grapegrowing|Comments Off on Passive Frost Protection

Stop HR 1161!

H.R. 5034 from last year, mockingly called the “Wholesaler Protection Act”, has morphed into H.R. 1161 this year. This bill would restrict the right of the consumer to purchase wine out-of-state and have it shipped to their home. The wholesalers would rather that you purchase your limited wine selections directly from them so that they get a cut of the profits from the sale.

If you would prefer to select your own wine and have the privilege of having it sent directly to your home, write your elected representatives and express your concerns!

Here are a few blogs that have written about this issue and links to their thoughts!

Tom Wark – “The Lies and Fallacies Behind the Wine Bill HR 1161”

Dr. Vino – “HR 1161: The Threat to Wine Shipping, Part II”

Vinography – “Why Every Wine Lover Needs to Call Their Representative in Congress”

UPDATED BLOG POSTS:

ShipCompliant BLOG (Guest Post by Wendell Lee of the Wine Institute)
HR 1161: The Great Constitutional Head Fake

ShipCompliant BLOG (Guest Post by Cary Greene of WineAmerica)
What Scholars Have to Say About the CARE Bill

By | 2017-05-19T21:03:38+00:00 March 29th, 2011|Current Events|Comments Off on Stop HR 1161!

2011 Grapevine Growth Begins with Budbreak

Budbreak (or budburst), is best described by using the BBCH-scale. This scale, is one of several that defines the phenological development (growth) of winegrapes, has assigned 2 digit codes and descriptions for every growth stage. These begin at 00 (dormancy) to 11 (first leaf unfolded) to 61 (beginning of flowering) to 89 (berries ripe for harvest) and ending at 99 (all leaves have fallen off the vine in late fall).

Budbreak occurs over a number of days – the length of this growth stage is determined by the variety, location and weather. Here are some of our own pictures to explain the stages of budbreak:

Growth Stage – Sprouting – Code 05 – brown “wool” clearly visible
Growth Stage – Sprouting – Code 07 – beginning of budbreak – green shoot tips just visible
Growth Stage – Sprouting – Code 09 – budbreak – green shoot tips clearly visible
Growth Stage – Sprouting – Code 09 – budbreak – green shoot tips slightly opened
Growth Stage – Leaf Development – some leaves unfolded

We will be adding the budbreak information from this year as it happens! Here is the information we have so far:

2009-2011 Budbreak by Variety
Chardonnay Viognier Malbec Cabernet
2009 March 15-21 March 22-28 March 29-April 4 April 5-11
2010 March 7-13 March 21-27 March 28-April 3 April 4-14
2011 March 19-28 March 26-April 2 April 4-11 April 7-16

2011 Order of Budbreak by Varietal:

Chardonnay
Petite sirah
Petit verdot
Viognier
Sauvignon musque
Sauvignon blanc
Zinfandel
Merlot
Malbec
Cabernet

This Spring has been an interesting mix of really warm and really cold weather that has definitely affected budbreak. It warmed as Chardonnay was in the middle of budbreak hastening that process while also encouraging the Petite sirah, Petit verdot and Viognier. Then it got quite cold and has stalled the rest of the varieties as the buds struggle to open. Another interesting year!

By | 2017-05-19T21:03:38+00:00 March 28th, 2011|Grapegrowing|Comments Off on 2011 Grapevine Growth Begins with Budbreak

Cork “Taint” Info

As chlorine-cleaning compounds have been found to be one of possibly several chlorine-containing substrates that are used by molds to create 2,4,6-trichloroanisole (TCA or “cork taint”), it would seem that we would all know by now to not use these compounds for winery sanitization (especially as there are other, just as effective, products without chlorine available). Unfortunately, the other halogens, bromine, flourine and iodine may be implicated also. Read a thorough review of the subject in this great blog article.

By | 2017-05-19T21:03:39+00:00 January 30th, 2011|Winemaking|Comments Off on Cork “Taint” Info