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Unpredictable Spring Weather Could Impact Fruit Trees In Utah

Fire blight is a bacteria disease that effects apples, pears, crab apples and hawthorn trees.

Spring weather in Utah can be unpredictable, creating frustration for people looking forward to summer weather. But for farmers, the up and down weather could impact the health of fruit trees. Experts are trying to warn people before it’s too late.

Fire blight is a bacteria disease that effects apples, pears, crab apples and hawthorn trees. JayDee Gunnell, a horticulture specialist with Utah State University Extension said the bacteria needs a natural opening to the tree. That opening is through the flowers and blossoms during this time of year.

“Disease needs three things to occur,” Gunnell said. “You need the host which is the plant, you need the pathogen which is typically always there, and then you need the right environment. For bacteria the right environment is warm and wet, which we currently have. With the blossoms being open, it’s a real concern for the bacteria to enter in.”

Gunnell said commercial growers are already aware of the fire blight risk.

“Our message is more for home owners, that if they have these certain species of trees that now is the time to protect those blossoms," Gunnell said. “The main way to prevent fire blight from entering into the trees is through a preventative antibiotic spray or a fixed copper.”

Gunnell said you can buy the sprays at any local nursery, but the window to prevent fire blight is short.

“You need to spray the tree while they’re in bloom and while the weather is wet and warm,” Gunnell said.

Many trees last year were effected by fire blight and Gunnell said they will be more susceptible this year. If you are too late, fire blight symptoms will show up about two weeks after bloom.

“What happens is the blossoms will darken and blacken and just kind of curl,” Gunnell said. “If you see that you can remove those at that time. Ideally you’d be pruning those infected areas out in the dormant season, about 8-10 inches below any visible darkness. Because it’s a bacteria and inside the plant it grows really rapidly, so that’s why you want to go below any visible symptom.”

Gunnell said crabapple trees can usually withstand untreated symptoms long-term, but pear trees will die if left untreated.