2019 WINTER WEATHER

Extreme cold may kill some emerald ash borer larvae but many likely to survive

Larvae show natural 'antifreeze,' protected by tree bark

The emerald ash borer, an invasive pest from Asia, has now been detected in 64 Iowa counties where it bores into ash trees and feeds on tissues beneath the bark, ultimately killing the tree.
The emerald ash borer, an invasive pest from Asia, has now been detected in 64 Iowa counties where it bores into ash trees and feeds on tissues beneath the bark, ultimately killing the tree.

IOWA CITY — This week’s extreme cold may spell doom for some emerald ash borers, but bark and a natural antifreeze will protect much of them.

Emerald ash borer larvae are able to survive subzero temperatures because of “supercooling,” meaning they can avoid the freezing of their internal fluids by creating “specialized sugars, alcohols, or antifreeze proteins,” according to a report Minnesota Department of Natural Resources. While the report lists a number of possible temperature ranges that could possibly kill off some larva, a study by the U.S. Forest Service and the Minnesota Department of Agriculture suggests it may be 13 degrees below zero.

“If they live in this area and they’ve been here before, even if they’ve been here a short time, they’re going to build up a natural antifreeze in the blood system,” said Mark Shour who helps teach emerald ash borer workshops with Iowa State University Extension and Outreach. “It’s almost like you putting antifreeze in the radiator of your car or truck ... the more antifreeze you got in that vehicle, the better it’s going to survive the cold winters.”

Although temperatures in Eastern Iowa are expected to dip below that minus 13 degrees mark this week, “it may take prolonged periods at a certain ambient temperature before temperatures beneath the bark will ever drop to the same level” to kill off much of the emerald ash borer population, according to the report.

“There’s going to come a point where the temperature’s going to be so cold that even your car or (emerald ash borer) larvae just can’t handle it anymore and it’ll freeze up. And so we don’t know what that temperature is but it’s possible that the cold temperature we’re experiencing could cause some mortality to (emerald ash borer),” Shour said. “My gut feeling is we may lose (emerald ash borer) larvae from cold, but it’s not going to wipe them out.”

l Comments: (319) 339-3172; maddy.arnold@thegazette.com

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