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April 12, 2012 Comments on Frost and Vineyard Management when Cold Temperatures are ExpectedI am posting comments that Mark Hart and Peter Hemstad made to the Minnesota Grape Growers listserv. I feel that they are right on target, so rather than paraphrase their comments, I am putting them on our web site as they have sent them (with their permission). Peter asked that I include a caveat that his comments are not aimed at the bud break delay work that Seth McFarland and our grad students (Issam Qrunfleh and Ben Loseke) have been doing, which he considers good work. I suggest reading Mark's and Peter's comments and take them to heart. Happy Frost Dodging and best wishes for a bountiful crop! Dr. Paul Read, Professor of Horticulture/Viticulture, University of Nebraska Mark Hart's letter: I had a couple inquiries in private about frost protection that I think stemmed from things I and others have said in the group. The first item would be frost protection using cryoprotectants, or products you spray on a vine prior to a frost event that are supposed give the vine extra protection during a freeze event. The short answer is that there is little evidence from scientific trials that these work. The way a scientific trial works is that the products of interest are compared side by side during a real freeze event and compared to control vines in the same location that have had no treatment. As you might imagine, these studies are a little hard to do, the research has to be set up and waiting for a somewhat rare event to occur. Since each freeze event is different in its nuances (duration, rate of cooling, humidity, etc.); the results seen in one set of circumstances might not be the same in a different freeze event. The field studies that have been done mostly show little positive benefit from these products. There are very few recommendations to use these products from the research/extension community. How can this be? If you go to any vendor/mfg website they are full of charts and graphs and testimonials about the positive benefits of their product(s). Because real world freeze events are rare, most vendors test their product on potted plants in freeze chambers. Those conditions do not mimic what is seen in the real world, and products that have performed well in these controlled conditions have rarely had similar performance in the field. Humidity in control chambers (and California) is generally much lower than what we see in the Midwest during freeze events. Every time I track down the details behind the testimonials, very few of the growers left a control area in their planting that was untreated, so the comparison the grower uses to evaluate the performance is to prior freeze events or to other growers in the general area. Again the variability between events and locations makes evaluating success on these bases pretty tenuous. If you Google search these products you will often find many examples of growers reporting failures - those don't show up in the marketing material. If a grower applies one of these products, I strongly encourage them to leave a few representative vines (same variety, same frost exposure) untreated so that they can compare apples to apples when evaluating effectiveness. There is some science that shows that plant tissue has different freeze tolerance based on its condition, and that those conditions might be able to be changed by adding something from the outside - so there is science that fosters hope for effective products, but field trials suggest that does not translate well to growing situations. Another aspect is spraying vines with cryoprotectants prior to bud break. This really is moving further from reality. IF these products worked, the basis is usually that the spray gets absorbed into or onto the green tissue to protect it in some way. Prior to bud break, there is not direct access to the green tissue, a product would have to be absorbed in some way to even have a chance of success. Dead bark and bud scales are very effective at NOT allowing that kind of absorption. That is why they are effective at protecting the plant tissue. We spray systemic herbicides (like Roundup) on our vines at this time of year. If those herbicides were absorbed through the bark, the vines would die. Those sprays use all types of surfactants which would enhance absorption, but the vines survive. Any cryoprotectant you spray on a vine before there is green growth is going to have the same degree of absorption. Use your money wisely. The other issue I want to discuss is site selection. If you go to an area like Europe where they have grown grapes for 100's of years, you will notice that vineyards are primarily in places that minimize the frost potential. Success and failure (selection) have worked over time to produce that pattern. In the North American Midwest our industry is young, and I don't think the site selection lesson has sunk in in our industry yet. As I look at the temperature reports come in I see some vineyards report temperatures that are 5-8 degrees above or below the temps recorded at the nearby airport station. Airport stations are usually flat locations that are neither in deep valleys or ridgetops and have an average temperature for the surrounding area, so that suggests that within a fairly small geographic region there is about 5-10 degree variance in the overnight lows that are encountered. Growers need to exploit these mesoclimate variances and locate vineyards where the frost risk is low. Site selection is the number one tool in frost avoidance. Once you have a vineyard in place, planted at a cost of $10-15K/acre, it is very difficult to decide to move, so site selection really needs to be impressed on potential growers at the start of the process. Hope everyone gets through the cold.
Peter Hemstad's letter: I would just like to encourage everyone to take Mark's comments to heart because I think he is absolutely correct with his analysis of the situation. Cryoprotectants are unproven and are unlikely to work. Growers who swear by them have very seldom left any untreated vines as a control. Without a control you have no idea if your buds survived because you sprayed them with a particular product or if they would have survived anyway. Peter Hemstad March 16, 2012 Early Bud Break and Possible Cold Weather DamageThe mild winter and unseasonably warm weather may bode ill for the Nebraska grape and wine industry. Early bud break can produce shoots from primary buds that are extremely vulnerable to damage if a cold temperature (frost or freeze) event occurs. Of course we all know that we can't alter Mother Nature/weather characteristics, but I thought repeating some information that has been presented at various workshops, conferences and elsewhere might be helpful. The potentially serious problem noted is not just worrisome to Nebraska growers, but the possible problem of early bud break followed by a cold weather event is of great concern in most of the East and Midwest, since similar weather patterns are being experienced throughout the region. Some of our growers are familiar with the work of Dr. Imed Dami (now at Ohio State University) and his colleagues where they have used sprays of a vegetable oil product (Amigo Oil) to delay bud break. In their work, 'Concord' was the most responsive, while the response of other cultivars to Amigo Oil applications varied greatly depending upon cultivar. Research work done at UNL by recent PhD student, Issam Qrunfleh has demonstrated bud break delay in 'Edelweiss' of from 5 to 7 days resulting from sprays of 10% Amigo Oil or 1,000ppm NAA (naphthaleneacetic acid). Likewise, Seth McFarland at Mac's Creek Vineyards has achieved good bud break delay by use of sprays of Amigo Oil on the Mac's Creek Vineyard grapevines. A synopsis of Dr. Dami's work and that of others, along with some additional observations has been sent to New York growers by Hans Walter-Peterson, Cornell University viticulture extension specialist, in which he addresses these concerns. I am attaching his write-up in hopes that it will be of interest to Nebraska growers and others accessing the University of Nebraska Viticulture web site. Additionally, the proceedings of a conference held in Missouri following the disastrous Easter Freeze of 2007 can be accessed here. Perhaps we will be lucky and not experience extremes of damaging cold following an early bud break, but I'm not holding my breath. If such problems occur, some of the information noted in the Missouri proceedings will be helpful. Please feel free to call or send emails to further discuss this potential problem facing our grape and wine industry. Good luck! Dr. Paul Read, Professor of Horticulture/Viticulture, University of Nebraska 2012 Conference Information Presentations Secure Online Registration (UNL CARI Registration Services) January/February 2012 VineLines – Conference Edition December 2011 Nebraska VineLines Happy Holidays to one and all! Paul, Steve, Christina, Ben, and Carola October/November Nebraska VineLines 2011 September 22, 2011 Machine Harvest Field Day Impresses Growers Attendees at the Machine Harvest Field Day at Ida’s Vitas Vineyards on September 19th were heard to say “you need to see this machine in action to really appreciate how effective it is, how it actually works!” The South Platte Grape Growers demonstrated the Korvan 3216 grape harvester to an appreciative audience that learned about the advantages (and challenges) of machine harvesting, including labor saving and timeliness of harvest. September 6, 2011 Pre-registration Form for ISH, 5th ISAEMP September 6, 2011 Directions to Ida's Vita's Vineyard August 19, 2011 AUGUST 27 MACHINE HARVEST FIELD DAY POSTPONED TO SEPTEMBER 19 The Machine harvesting Field Day originally scheduled for Saturday, August 27 at Ida's Vitas vineyard near Ogalala has been re-scheduled for Monday, September 19 at the same location. The re-scheduling was necessitated by serious weather-related events and a delayed harvest maturity of the grapes to be harvested. Registration will begin at 9:30 a. m. followed by demonstration of the machine harvester in the vineyard at approximately 10:15 a. m. Discussion of the pros and cons of the use of a machine harvester will take place over lunch and in early afternoon. Cost of the Field Day is $15 (includes lunch). Directions to the vineyard will soon be posted on this site. This is an excellent opportunity to observe a grape harvester in action and to evaluate its potential for use in Nebraska vineyards. June 20, 2011 April 13, 2011
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