Apple trees in Northwest Michigan are dying from a bacterial disease, and the issue continues to grow.
Fire blight is becoming prevalent with climate change. The disease is not typically a problem when springs are a cool temperature. But as Michiganders have noticed, spring has warmed up.
The Coordinator of Northwest Michigan Horticultural Research Center, Nikki Rothwell, is working with the U.S. Department of Agriculture to research and combat this issue.
She said the disease has been found to be common in counties such as Manistee, Leelanau, Benzie, Grand Traverse and others surrounding the Lake Michigan area.
Rothwell said fire blight builds up on the flowery bits of an apple tree during bloom when it is warm outside. And when the rain comes, or heavy dew appears, the bacteria gets washed into the flower which will spread throughout the tree, killing the plant.
Lately, Rothwell has noticed some days with dew and pop-up rain showers. Just last week, she said the research center located in Leelanau County experienced hail. When the apple trees are exposed to hail it causes trauma. Leaves get torn from the frozen raindrops which allows the fire blight to spread within the tissue of the plant in a different way.
Fire blight has “never” been an issue in Northern Michigan, Rothwell said.
However, with climate change and warmer springs, growers are dealing more regularly with the disease.
Rothwell said this is also because the modern high-density systems for apple orchards that are used today, are much more susceptible to fire blight than the older system. The newer system plots the smaller trees closer together. Whereas the bigger trees that used to be grown were further apart, which decreased the risk of fire blight.
“Those orchard systems to put in those modern high-density systems are typically around 20 to 25,000 dollars an acre,” she said. “If you lose even a tenth of those trees, you know, financially that’s a huge blow.”
So, why use the high-density systems? Rothwell said there have been economic studies that prove the high value of apples grown this way. Smaller apple trees tend to flower as soon as they can to produce crops. However, bigger trees take years to flower which makes them less profitable.
Rothwell said those advantages outweigh the challenges with fire blight.
In Rothwell’s collaboration with the USDA, she said they are trying out different biologics in attempt to resolve the disease. There was a focus on antibiotics initially, however, people need them for human medicine.
“We’re trying to think about alternatives,” she said. “We are looking at plant growth regulators, we are also looking at things from the genetic point of view. Can we identify the gene that triggers resistance to fire blight, materials, and figure out if we can make the tree resistant itself.”
Fire blight has developed a resistance, Rothwell said. This means it is harder to control and get rid of as it spreads regardless of the species. To combat the lack of ability to use human antibiotics, they are looking at “how to control fire blight naturally.”
Additionally, Rothwell said they are potentially trying to breed new apples or older apple varieties that won’t be susceptible to fire blight.