“In my time, (the emerald ash borer) has had a significant impact on the loss of trees here,” said Cody Powell, Miami University’s Vice President of Facilities Planning and Operations, who has worked at the school since 1994.
The emerald ash borer, also known as EAB or Agrilus planipennis, is a beetle species originally native to China and eastern Asia. The species was first found in the United States in 2002 and has rapidly spread throughout the country. 33 states across the country have reported infestations, from Colorado to Connecticut, and the beetle has killed hundreds of millions of ash trees. The problem is so widespread that the Department of Agriculture has called the ash borer “the green menace.”
The first reported case of ash borers in Ohio came in 2003. The Ohio Department of Agriculture originally tried to quarantine the beetle to the northwest region of the state to limit its impact. But by 2011 there had been reported sightings in every county in Ohio and the quarantine was dropped.
EAB kills trees by planting eggs in the bark. As the larva grow, they eat the inside of the limbs and prevent the tree from growing. Once a tree has been infected by the beetle, it usually dies within a few years.
All species of ash trees are vulnerable to the ash borer.
According to David Carey, a biological science technician with the US Forest Service in Ohio, only 1 in 10,000 trees will be completely avoided by the ash borer.
Carey and other researchers are studying those trees that have survived attacks to see if their traits can be passed along to other trees.
“With enough survival trees, we hope to breed them and implement these defense mechanisms on other ash trees,” he said.
Carey also said that this time of year is the best opportunity to take preventative action against the ash borer. The beetles mate during the beginning of summer and plant their eggs inside the bark of ash trees. Their larva require a certain number of “growing degree days,” when the temperature is above 50F, to begin eating the tree and emerging as adults. Applying pesticides and treatment in the early summer lets the trees begin to grow before the pressure of the EAB becomes overwhelming.
Miami University has focused mainly on saving the largest and most iconic trees on campus. Battling the infestation was one of the reasons for the restoration of Bishop Woods in 2015.
“We have an unbelievable amount of ash trees on campus,” Powell explained, “and treating all of them was not feasible.”
Carey agreed on the benefits of focusing on the preventative treatment for some trees. “For specific, high-value ash trees, there are pesticides that are effective,” he said.
Most of the treatment work being done is to prevent the further spread of damage. Infected ash trees usually die within a few years of the initial damage. Once the damage has extended to the crown of branches at the top, like in the tree in front of Kumler, it is likely beyond saving.
The exact timing differs based on the temperature in the region and the type of pesticide being used to combat the borer. In Butler County, it’s recommended to apply treatment before the beginning of July.
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