As we all know, the Midwest and the Northern Plains have been hit by some bitterly cold winter weather this week, and although it could have been deadly for any living thing, there is hope it will indeed be deadly for a most hated non-native insect called the Emerald Ash Borer (EAB) (Agrilus planipennis Fairmaire).
Since 2002, the EAB has spread its devastation east and west from Michigan. Here in Wisconsin, the entire state has been quarantined against this aggressor. Adult beetles lay their eggs on the tree bark. Their larvae bore below the bark and into the xylem beneath. There they feed on the ash tree cutting off pathways for water and nutrients and causing the tree to slowly die. Fortunately for us, the larvae do not appear to be able to withstand temperatures of minus 20 degrees Fahrenheit inside the tree. So this winter, with its cold temperatures, may bring some relief from the devastation caaused by this insect. (USFS)
Cold temperatures between minus 20 to minus 30 degrees Fahrenheit should have a slowing effect on the devastation. In areas with more than minus 30 degrees Fahrenheit weather, the USFS is hoping for a more major impact. The hardiest of the insects, however, will still survive the cold so the extreme cold will likely not totally eradicate the EAB.*
How can insects withstand such frigid temperatures? Insects have natural cryoprotectants** which shield them from cold weather. In the case of the EAB, the trees themselves provide insulation regardless the weather. Their thick bark can provide up to 5 degrees of insulation. A covering of snow against the trees, and radiant heat during the day from sunshine provides even more protection from the cold.
*Research from Michigan State University shows the EAB actually arrived in the 1990s or earlier, well before its destructive damage began to show up in America’s ash trees. It took many years to build up a destructive population, so even if the cold sets them back, EAB may very well become a destructive force again.
**According to Wikipedia, cryoprotectants are substances used to protect biological tissue from freezing damage due to ice formation. Insects, like fish and amphibians, create cryoprotectants (antifreeze compounds and antifreeze proteins) in their bodies to minimize freezing damage during cold winter periods.