Asia has given us many things that we enjoy. Nearly every invention has its roots with the Chinese and Japan and South Korea have greatly influenced our culture. For trees here in North America they are not so happy with Asia. The fungal blight that has decimated the American chestnut tree came from Asia and a newer threat has arisen as well. It is the emerald ash borer beetle.
The emerald ash borer is a beetle native to northeastern Asia. Females lay their eggs in crevices of the bark of ash trees and emerge about two years later. The average female can lay between 40-70 eggs. The larvae hatch and chew through the bark into the tree where they feed while turning into pupae. In the spring time they chew through the bark to emerge as adults leaving a D-shaped hole in the bark. Adults are bright green in color and grow to be about 8.5 mm long. They are commonly misidentified as other species of beetles but are the only beetle found in North America with a bright red abdomen. The species is common in Asia but not in enough numbers to signify a threat to the native ash tree population.
The borer was first cataloged by French naturalist Armand David while traveling in China in the 1860s. They are common in more temperate climates like in Russia, Mongolia, China, Japan and the Korean Peninsula. The emerald ash borer migrated west and was found in Moscow in 2003. It has since spread into Sweden at a rate of 25 miles per year and will reach Central Europe in the 2030s. The beetle has also been found in Michigan in 2002 after being accidentally introduced when it hitched a ride on wood coming from Asia and has spread all over the US and Canada in 31 states and three provinces.
Several species of ash trees are vulnerable like the green ash, black ash, white ash and blue ash. In Europe and North America it has become an invasive species and little is known about it. Once the emerald ash borer infests a tree that tree has about ten years to live. Adult borers actually pose little threat and simply nibble on the tree’s leaves but the larvae feed on the inner bark which disrupts the tree’s ability to transport water and nutrients. Some blue ash trees have been found to offer resistance but it only prolongs the tree’s life but Chinese ash trees have been found to be resistant. Populations of the beetle spread through both flight and transportation of ash wood for use as firewood or for a nursery which has prompted PSAs aimed at not moving firewood. The beetle is also very hearty. It can survive temperatures as low as -22 degrees Fahrenheit and as high as 127 degrees Fahrenheit.
Ten million ash trees have already been killed and the other approximately 8.7 billion are at risk. In Europe with the loss of the ash tree more invasive plant species are taking over and the soil is found to be changing. Some municipalities are becoming overwhelmed trying to remove infected ash trees and have turned to insecticides to slow the emerald ash borer. Even in areas where the beetle has not been spotted they are on high alert. In North America a wasp that feeds on the emerald ash borer (and other beetles) has been introduced and volunteers are being tasked with watching the wasp to see what it brings back to its burrow. Woodpeckers also hunt the borer and heavy woodpecker damage to a tree can be a sign on infestation.
In infected areas quarantines are in force from the USDA and other regulatory agencies to prevent potentially infested ash wood from being moved out of the area. These quarantines are in effect in nearly every state that the beetle has been found in.