Earlier this week many people were likely cursing the below zero degree weather that spread across the United States. However, entomologists could not be happier about the frigid climate. The cold weather is a welcome change this winter as some of America’s most resilient invasive insects may die-off by freezing to death. The most environmentally damaging invasive insects in America include the emerald ash-borer, the gypsy moth and the wooly adelgid. These invasive insect species have been of serious concern to environmentalists for the widespread damage that they have been inflicting on living trees. For the past several years populations of non-native insects have been growing substantially, and the damage they have been causing to forested regions is noticeable to anyone who has visited a few national parks. Although invasive insects, like the emerald ash-borer, are relatively resilient when faced with freezing temperatures, entomologists are more hopeful than ever when it comes to decreasing the environmental damage caused by invasive insects. However, this is not to say that these insect pests don’t possess remarkable abilities that allow for their survival during bouts of extreme cold.
Entomologist Tom Tiddens works at the Chicago Botanic Garden where he is currently studying how emerald ash-borers are responding to the current freezing conditions. Ash borer larvae kill healthy trees by depriving trees of water as well as cutting off their circulation. These insects accomplish this by boring deep into trees. However, these insect pests surface underneath a tree’s bark during the winter, which makes them more vulnerable to harsh climatic conditions. Unfortunately, temperatures have to drop to twenty to thirty degrees below zero before ash borers succumb to the cold. Like several other insects, ash borers survive the extreme cold due to a physiological ability known as “supercooling”. In order to avoid freezing to death, ash borers will purge themselves of all of their stomach contents so that food and water does not freeze inside of their bodies. This gross process also allows ash borers to fold themselves in half, which reduces their body’s surface area. The reduced surface area helps to protect them from the extreme cold, and they become better insulated after folding. Despite the cold temperatures that are required to kill-off ash borer populations, Tiddens believes that up to eighty percent of ash borers in Minnesota and other northern regions have already died as result of the recent cold spell.