A small green beetle could be responsible for the destruction of all 7.5 billion ash trees throughout Canada and the U.S. It has already ravaged 100 million ash trees across 14 states and parts of Canada, leaving their bark brittle and trunks dying from the inside out.
Without the ash tree, which is usually grown in urban areas for its ability adapt to high-stress environment, 10-25 percent of “urban canopies” that help protect cities from pollution, could vanish. In cities that have been hit by the EAB such as Minneapolis, Minnesota, recent studies have shown that heart attack rates and lung disease deaths have increased.
Many biologists are comparing the rapid destruction of ash trees by this beetle to Dutch Elm Disease and the Chestnut Blight. Dutch Elm disease, also caused by an invasive insect, nearly caused Elm trees to go extinct in the early 1900s. The Chestnut Blight, caused by an invasive fungus, likewise wiped out the entire population of adult Chestnut trees from their historic lands during the same period.
The emerald ash borer beetle (or EAB) is a small, bright green invasive beetle species that is highly destructive to ash trees. The EAB is thought to have been transported to America in the early 2000s via wooden crates shipped from East Asian countries such as China and Korea.
Like most insects, these beetles go through several growth stages. The larval stage is the most destructive of the EAB’s life cycle. Larvae tunnel under the bark of the tree where they feed on the soft wood underneath, cutting off the tree’s water and nutrient supply, slowly starving and killing the tree.
An infestation can kill an ash tree within three to five years after the adults laid the first eggs – within eleven years they can destroy an entire ash tree forest.
Now the main concern of many biologists and government officials is quarantining the beetle. Parks throughout the U.S. have begun to ban individuals from bringing in outside firewood. Transporting firewood risks transporting the EAB.
“The emerald ash borer beetle lives underneath the bark of ash firewood, and when it’s moved from one place to another — say, from your home to your campsite — you’ve just given the pest a free ride to a new location,” Sharon Lucik of the USDA Animal and Plant Health Inspection Service (APHIS) explained in a prepared statement.
Ohio has been one of the hardest hit states. Sixty-seven of its eighty-eight counties have been infected by the EAB. A recent and powerful storm in South Eastern Ohio downed many trees and cut off power for days. The EAB has been blamed for weakening many of the trees that fell during the storm. One property owner, Mike McClain, began noticing problems with his trees three years ago “It’s a silent killer,” he said in a report by the Dayton Daily News.
Ohio is not alone however; states such as Minnesota, Wisconsin, Illinois, West Virginia and Michigan have also suffered from the invasion of the EAB. Weakened trees have resulted in large limbs falling on homes, cars and even people.
Focusing on halting the spread of the beetle by encouraging quarantine of firewood, and stopping firewood transport is just one part of the solution.
Meanwhile, scientists and biologists have been working on creating insecticides to kill the beetle and save trees. Three insecticides have shown positive results: Emamectin, Midacloprid and Dinotefuran. Emamectin is injected directly into the tree trunk, while Midacloprid and Dinotefuran are mixed with the soil around the base of the tree and its roots.
Scientists are also working on finding and releasing a natural enemy of the EAB. Several have been found and released, but so far an Asian wasp and natural parasitic predator of the EAB, T. planipennisi, has been the most effective. The wasp kills the EAB larva before they can do enough damage to destroy a tree. In studies, the wasp only parasitized the EAB and rejected other insect hosts. Experts hope this will keep the wasp from further impacting affected ecosystems decimated by the EAB in any negative or unpredicted way.
Photos courtsey of USDS, David Cappaert Michigan State University, Bugwood.org, Leah Bauer, USDA Forest Service Northern Research Station, Bugwood.org, Houping Liu, Michigan State University, Bugwood.org, Wisconsin Department of Natural Resources, and Lillian Steenblik Hwang
