If you grow grapes in the Midwest, the last thing you want to think about in February is spraying your vines. When you make 10 to 15 applications per year, you relish the break that the cold weather brings. I like going down into the workshop and seeing the spray rig put away for the year.
But this season I'll be adding another spray to the schedule. In mid-February, I'll be applying a spray of 8% soybean oil. The reason for this spray is to delay budbreak in an attempt to avoid damage from spring frost events. I recently saw Imed Dami of Ohio State University give a convincing presentation on the affects of spring oil applications. Dami who puts out a useful grape-wine newsletter at OSU, studied both stylet oil and vegetable oil, and the latter had fewer problems with pytotoxicity and reduction in yield. But at a rate of 8% or less, vegetable (soybean) oil sprays delayed budbreak anywhere from 2 to 19 days under the right conditions. Also, vines deacclimated slower. Deacclimation is the process of getting ready for spring, and vines that start this process are more susceptible to freeze and frost events. Dami recommends using a spreader-sticker like Latron B-1956 at 1% along with your 8% oil. He says that you can spray 200 gallons or more per acre.
The best way to keep your buds from getting fried by frost events is to do whatever you can to delay budbreak. That means pruning as late in the season as possible, or even rough pruning, leaving longer spurs or canes; the buds on the end of a spur or cane will break first, delaying those closer to the trunk. If you leave long canes, it could delay some of the buds you intend to keep by a few days.
So late pruning, rough pruning and oil applications are three methods to keep those buds from breaking until after frost danger has passed. It's a lot more work, and it may help or it may not be necessary. In the worst case scenario, you can do all these things and still experience damage. But that's the nature of nature.
One note on the spray rig in the photo. That's what I use for my test vineyard, and it will probably get me through my first pair of seasons in my 1/2 acre planting. After that I'll want to switch to an airblast sprayer to make sure I get good coverage on the fruit, since vinifera is more sensitive to diseases. It's an ATV sprayer that runs on a 12 volt battery, plus a gas mask, rubber boots, chemical gloves. I pull it up and down the hill in a hand cart. Only the disposable plastic suit is missing. I really hate all this stuff, but you gotta do what you gotta do. If I someday strike it rich I'll move somewhere where I don't need to spray.