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Michigan apple growers see threat of climate change crisis through spread of fire blight

Michigan apple growers see threat of climate change crisis through spread of fire blight

- Fire blight is a bacterial pathogen that spreads easily during blooming season

- Threat looms larger as climate crisis brings longer, warmer and rainier springs

- Disease poses a particular threat to cider apple growers

Patrick and Sara McGuire have been growing apples since they were married 25 years ago. Their 150 acres in Ellsworth in northern Michigan— dubbed Royal Farms — are a mix of sweet apples and the bitter varieties suited for making hard cider.

Last spring they put in a new crop of Honeycrisps, one of America's favorite apples, only to discover an unwelcome visitor just a few weeks later: a bacterial menace known as fire blight.

"We actually removed about $10,000 worth of trees by hand," Patrick McGuire said. "It might've been 25 percent of that lot."

Fire blight is a bacterial pathogen that spreads easily during blooming season. It has the potential to kill not just individual trees but entire orchards. Though not a new problem for apple growers, it's been looming larger as the climate crisis brings longer, warmer and rainier springs that expand the window for it to infect trees.

The disease poses a particular threat to cider apple growers. Terry Bradshaw, a research assistant professor at the University of Vermont, said they are at risk because the European varieties they rely on are biennial, making them especially vulnerable to fire blight. "[They will produce] a lot of fruit in one year and a little in the other," Bradshaw said. "It's just wall-to-wall blossoms during bloom—those are a whole lot more targets [for the bacteria] to hit." Making matters worse, they bloom later in the year.

If one crop of cider apples is lost to fire blight, it will be two years before those trees produce again, he said. And with a 10-year pipeline from ordering trees to producing fruit, that kind of setback could prevent growers from staying afloat.
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