there’s a high variability in air temperatures between frost pockets and higher terrain in the vineyard,” he noted.
“They take advantage of layering. For instance, -25 C can be a critical point for some buds, so you begin seeing substantial damage. If a wind machine can add a degree of two of temperature, the damage can be prevented,” he said.
In his report from a survey of damage from the 2008-2009 winter for the B.C. Wine Grape Council, Bogdanoff reported that “a temperature difference of 4 C between low-lying vineyards and those above on sloping hillsides was the difference between negligible and substantial bud injury.”
In that report on winter damage he also noted that “A 2 C to 4 C gain in heat during a -20 C event can make large differences in the levels of winter vine damage.”
He’s said he’s seen instances where vascular damage can be caused to just one side of a vine because of a difference of a degree or two of cold within the vineyard; or you can lose a cordon. Then you know you’ve lost a significant number of buds, too, he said.
If frost-tender vinifera grapes are planted in the best sites you can avert cold damage, he added. “It’s a fine line.”
However, cultural practices can also make a difference. For instance, if you push the vines and water them right to the end in the fall, then there’s a frost, the buds are not as hardened off and you could suffer more damage, he noted.
“As the wine industry expands, it moves into marginal land and people plant more marginal varieties,” he added.
Bogdanoff said they have found winter damage from cold temperatures last Nov. 23 to some grape varieties, particularly those that were harvested late.
“The buds weren’t quite a hardy as they would have been in December or January. They’re at their hardiest then, so they’re less vulnerable to cold.”
They’re now looking at vineyard management practices that will
10
Smaller machine a big hit with OK Falls cherry grower
By Judie Steeves A
fter six years of consistent bad luck in which the cherry orchard barely produced anything, Glen Hall says it was a question of whether to cut the trees out or spend some money and try a new method of frost
protection.
That was four years ago, and since the Okanagan Falls orchardist bought a Shur Farms Cold Air Drain, he’s had pretty good crops every year. He uses it in spring to protect the buds and blossoms from frost. He sets it up for a threshold of 3 C at the pink stage until there’s no more frost. During March and into April if temperatures are dropping and the forecast is for a clear night, he gets it going, using the PTO hitch on the tractor. There are options for an automatic start, but they elected not to spend the extra money, he says.
Instead of using a large fan blade high in the air to mix the layers of warmer and colder air, this machine draws air off the floor of the orchard and thrusts it upward. It’s only eight feet tall and can be moved around the orchard. Not only does it have a lower profile than a wind machine, it’s also quieter because it uses a smaller motor and it costs less money, notes Hall. Prior to purchasing this equipment, he’d used sprinklers for frost protection, but he found they didn’t work that well. He’s been growing cherries for about 10 years, beginning with a couple of acres, then expanding to four and now seven acres. He admits it’s the location and variety that are his problems. He should never have planted Lapins in what has proven to be a frost pocket. Other parts of his orchard are higher, and he now realizes why there weren’t cherries planted there when he took over, he says wryly. But, in spring a couple of degrees can make the difference between a nicely-thinned crop and no crop at all.
Although he admits to sustaining some frost damage since he put it in, he says it hasn’t been enough to matter. The new machine has proven itself in his eyes.
enhance the hardiness of grapes. He also pointed to the usefulness of the WSU bud hardiness data, which advises growers when to turn wind machines on.
He noted that buds can react pretty quickly to a spot of warm
weather. If it’s followed by a sudden plunge in temperatures, that can also be dangerous.
Often that kind of damage takes the primary buds first and they are the most productive, so pruning must be altered to compensate.
AGRICULTURAL NETS & FABRICS
www.farmsolutions.net neal_carter@telus.net
250.494.1099 British Columbia FRUIT GROWER • Spring 2011
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