America’s top apple-growing regions are grappling with significant challenges brought on by a changing climate, according to a study from Washington State University (WSU). Researchers examined more than 40 years of climate conditions that affect the growth of apple trees.
Many growing regions currently face increased climate risks, but the three largest apple-producing counties in the United States were among the most impacted. They include Yakima in Washington, Kent in Michigan, and Wayne in New York.
With over 48,800 acres of apple orchards, Yakima County is the largest of the three. It has experienced concerning trends in five of the six metrics the researchers analyzed: bud break, flowering, fruit development, color development, and maturation.
“We shouldn’t take the delicious apples we love to consume for granted,” said Deepti Singh, a co-author of the study and a climate specialist at WSU.
“Changing climate conditions over multiple parts of the growth cycle pose potentially compounding threats to the production and quality of apples. Moving forward, it would be helpful to think about adaptations at different stages of apple growth that can minimize overall harmful impacts.”
In addition to the six metrics, the team looked at two other metrics—extreme heat days and warm nights. The first is defined as days with a maximum temperature above 93 degrees Fahrenheit, which can cause sunburn and other issues, while the second is when minimum temperatures at night are greater than 59 degrees Fahrenheit, which can alter the fruit’s coloration.
The researchers also took the number of cold days into account. Any shifts in these metrics can negatively impact the production of apples by changing the time when apple flowers bloom, elevating the risk of sunburn on apples, and affecting the appearance and quality of apples.
The strongest trends were found in the western region of the U.S. The challenges of maintaining apple production in the midst of climate change are made all the more complex when considering that apple trees are perennials.
“What goes on in different seasons can affect long-term health as well as the performance and productivity of the apple tree during that specific season,” said Lee Kalcsits, a tree physiologist at WSU.
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“So what goes on in the winter affects what happens in the spring, which affects the summer, and it just keeps going around in a cycle.”
In the state of Washington, growers are already adapting to the more extreme heat of today’s climate by incorporating techniques like netting and evaporative cooling to prevent sunburn.
Researchers plan to look at projections to inform future management strategies in the tree fruit industry. As climate risks become more likely, it is important to come up with ways to help the industry adapt and protect this beloved fruit.
The study was published in Environmental Research Letters.
