By Megan Tarter
Grape growers should be aware of the potential for April frost damage following unseasonably warm weather in March, a Purdue University viticulturist says.
Widespread damage occurred in 2007 and 2012 when warm temperatures in March were followed by freezing temperatures in April, said Bruce Bordelon, professor of horticulture.
"Obviously, this year we have had a warm February and March, so it is very possible that we will have early bud break and the potential for freeze damage this year," he said.
April has started off colder than normal across much of Indiana with temperatures falling into the mid-20s F in some areas.
Managing freeze risk
Growers have an option to manage freeze risk. Long pruning, also called double pruning, helps avoid spring frost and freeze damage, especially on varieties that bud early. This technique calls for growers to avoid pruning canes until after the last probable spring freeze has passed.
Growers should select canes during routine pruning practice and leave them long, with 10-15 more buds than desired. These extra buds will help slow development and compensate for potential loss to frost and freeze events. After the last probable freeze, the canes can be shortened to the desired length.
Long pruning is advantageous because it leaves secondary shoots as a backup if the primary shoots become damaged.
"Even though secondary shoots are not as fruitful as primaries, the large number can result in near-normal yields," said Bordelon. "This was the case in our research plots in 2012, and we were able to produce a full crop on almost all varieties despite essentially complete loss of all primary shoots."
While this method requires producers to make extra trips through the vineyards, Bordelon says it could make the difference between a bountiful crop or not.