Roots of resilience: the experts working to bolster apples against the climate crisis

"We got a warm-up in February, and then a big cold air mass moved into New York and pushed all the way down into the fruit-growing area of Pennsylvania, he recalled. In the spring, we started seeing tree damage. Some scientists named the phenomenon rapid apple decline. Robinson and his colleagues concluded that the sudden drop in temperature, as much as 65F (18C) in a matter of days, had shocked the orchards, which had started to emerge from dormancy due to the earlier warmth."

"They also found that the most critical damage wasn't to the trunks or limbs, but instead to the rootstocks, the very foundations of the trees. Those foundations are often quite old. The widely planted M9 rootstock, for example, was developed at England's East Malling Research Station over a century ago. But as extreme weather driven by the climate crisis continues to accelerate, scientists like Robinson are growing concerned that time-tested rootstocks may not hold up against the tests of decades to come."

"Damage to rootstocks means damage to a US apple industry that generates roughly $23bn in annual economic activity and yields over 11bn lbs of the country's most-consumed fruit. That's because nearly all commercial apple trees are actually a combination of two separate plants. The apple-producing part of the tree, called the scion, starts as a cutting from a variety like Gala or Red Delicious. Nurseries then remove all but a small portion of a different tree, the rootstock, and graft the scion on to that base."

A warm February followed by a major cold air mass moving into New York and down into Pennsylvania caused tree damage in spring. Scientists identified the event as rapid apple decline, linking it to sudden temperature changes of up to 65F (18C) within days. Orchards had begun emerging from dormancy due to earlier warmth, making them vulnerable to the later cold shock. The most critical damage occurred in rootstocks rather than trunks or limbs. Rootstocks are often long-established varieties, such as M9 developed at England’s East Malling Research Station over a century ago. As extreme weather accelerates, researchers worry these rootstocks may not withstand future climate-driven tests. Commercial apple trees rely on grafting scions onto rootstocks, so rootstock damage threatens the US apple industry’s economic output and supply.

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