Monday, April 01, 2019

Climate change is already hurting fruit breeders, and consumers could soon feel the pain

By Adrian Higgins
March 28, 2019


Growing fruit trees in Appalachia has always been a high-wire act as peaches, plums, apples and pears race to flower in early spring while dodging a killing frost.

But researchers across the United States say the milder winters of a changing climate are inducing earlier flowering of temperate tree fruits, exposing the blooms and nascent fruit to increasingly erratic frosts, hail and other adverse weather.

The problem is not obvious to consumers, in part because a harvest collapse in one region can be masked by a bumper crop in another. But unless breeders can produce more climate-resilient varieties, fruit-growing regions of the United States will be seriously disrupted by future warming scenarios, scientists say.

Breeders are working to develop new varieties, said Katherine Jarvis-Shean, a University of California plant physiologist and farm adviser. But new trees typically take two decades of methodical breeding to create, exposing existing varieties to the vagaries of shifting winters and springs. “The consumer will begin to know it’s happening in the coming 10 to 20 years,” she said, and got a foretaste five years ago when the sweet cherry crop in California crashed after a winter that was too mild.


Spring blossom freezes in Kearneysville “would happen before, occasionally,” said Demuth, a research technician. “But to have it happen in back-to-back-to-back years, it’s never happened before in the 23 years I’ve been doing this here. To lose four years in a row? Yeah, heartbreaking.”

“There’s no question that the winters have become warmer and the spring weather more erratic,” said Michael Wisniewski, a plant pathologist at the research station, which is part of the Agricultural Research Service. “There’s great concern about the suitability of cultivars and adapting them to climate change.”


The obvious peril is of killing frosts to blossoms that have awaked too soon. Another major concern is fruit and nut trees with high chilling needs will not get enough accumulated cold to thrive after the winter. This is the greater worry in California’s Central Valley, the nation’s principal fruit and nut producing region.

Trees that are insufficiently chilled bloom poorly and sporadically. The fruit quality is compromised, and trees may become so stressed that they die, scientists say. Some long-winter varieties in South Carolina did not leaf out last year after two mild winters. “That was alarming to us and to growers because we hadn’t seen it before,” said Ksenija Gasic, a peach hybridizer at Clemson University.


She said an insufficiently cold winter used to occur every 15 years or so, but California has seen two in the past five winters, Jarvis-Shean said. In 2014 the sweet cherry crop fell by 63 percent as a result.

Some researchers say growers in the Central Valley eventually may have to consider moving farther north or to higher elevations to produce the same crops.

Lack of winter chilling and spring blossom freezes are obvious problems, but climate change is bringing a range of other difficulties for fruit growers. Pests and diseases may spread, warm nighttime temperatures in fall reduce fruit quality, hot days in winter cause sunburn to plant tissue, and extreme weather events such as floods pose other risks.

In the recent low-chill winters in California, male, pollen-bearing pistachio trees bloomed out of sync with the female nut-bearing varieties, reducing the crop, Jarvis-Shean said.


An underlying worry, he said, is that fruit breeding programs will not be able to keep pace with rapid climate change. It can take 15 to 30 years to create a new commercial apple or peach variety from scratch.

In New York, Brown said, the challenge facing breeders is not lack of winter chilling but how to create varieties that can deal with the roller-coaster warming period in the weeks leading up to bloom.


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