Fire blight is a bacterial pathogen that spreads easily during blooming season. It has the potential to kill not just individual apple trees, but entire orchards. It is of course not a new problem for apple growers, but it has 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,” said Bradshaw. “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.
According to Nikki Rothwell, a specialist with the Northwest Michigan Horticulture Research Center at Michigan State University, the climate crisis isn’t just problematic in terms of fire blight, but also because it’s allowing for more generations of insect pests each year.
“If growers cannot mitigate risk in some way, fruit farming is not a sustainable model or business,” she told seattletimes.com.
Fire blight is easily spread by wind, rain and insects, so stopping it one part of a grower’s orchard can be key to reducing the chance it will other trees. “Fire blight was not typically a problem in northern Michigan, because we’re so far north and these bacteria really love warm weather,” said Rothwell of Michigan State. “That’s really changed.”
Photo source: Extension.unh.edu