Low chilling hours plus unseasonably temperatures a ‘hot-topic’ at conference
Writer: Robert Burns, 903-834-6191, firstname.lastname@example.org
NACOGDOCHES – Unseasonably warm weather, up to the mid-70s and even low-80s, can be a double whammy for growers of peaches, blueberries, blackberries and other fruit crops, according to a Texas A&M AgriLife Extension Service expert.
“This heat wave we’re currently having in East Texas is not good. It makes us glad we’re not living in New York, but it’s not good for the fruit industry,” said Monte Nesbitt, AgriLife Extension horticultural specialist, College Station.
Nesbitt was a speaker at the East Texas Fruit and Vegetable Conference held Feb. 16 in Nacogdoches.
First, there’s the risk for crops that have accumulated enough chilling hours to come out of dormancy and begin forming buds or fruit, Nesbitt said. If they then get hit by a late freeze, it can kill the new growth and developing flowers, and as a consequence, fruit production is severely knocked back.
Chilling hours refers the number of hours of cold temperatures during the winter that fruit trees “need to satisfy winter rest requirements and produce a good crop,” Nesbitt explained.
A week ago, many areas of Texas were on track for chilling, though some were shy of the number needed for a particular fruit crop, such as peaches, he said. The hope then was that a few more cool nights would boost the number of needed chilling hours.
“But once we have a warm spell like this, a fruit crop’s accumulation of chilling hours is halted,” he said.
This means fruit production may not be just at risk of freeze damage, but limited by lack of chilling hours as well.
But the risk of a hard freeze occurring after budding is a real possibility. Late freezes in 2013 and 2014 caused widespread fruit production losses in many areas of the state.
“I polled the conference East Texas audience, and most indicated they believed that a late frost is possible for this spring,” he said. “I hope we all turn out to be wrong about that. But we really don’t know, if we don’t get another freeze, we could be fine.”
A map showing average last spring frost dates for different parts of the state can be found on the Aggie Plant Answers webpage at http://bit.ly/1SSkSXC .
There’s not a lot growers can do when faced with lack of chilling hours. But for peach growers, the later they can delay pruning, the better, Nesbitt said.
“Pruning can slightly stimulate bud activity, and growing buds are more susceptible to a late frost or freeze,” Nesbitt said. “And you’re also removing branches or limbs that can help protect the lower parts of the tree in certain types of frosts.
“Our problem in Texas is that once chilling has been satisfied, warm temperatures cause buds to break dormancy, making us vulnerable to late frost. Pruning can work against us in that regard. Wait as long as possible — until after the last frost to prune; it’s okay to do that.”
As for pecans, they are the bright spot in an otherwise potentially gloomy forecast, he said.
“Pecans require more heat units to break dormancy, so they are less likely to be hurt by late freezes than most of the other fruit crops,” Nesbitt said.