Montgomery County park officials expect to remove about 1,800 trees due to an insect infestation in ash trees.
A horticulturist for Montgomery County parks, Patrick Harwood, said this number would likely grow.
“This situation will evolve as the infestation spreads, so we may move upward to 2,000 to 2,500 this year if we can receive funding for it,” Harwood said.
The insect, the Emerald Ash Borer, goes into the tree, where it lays its eggs, which become larvae. The larvae feed on the cambium layer of the tree, which lies just below the bark. This prevents the distribution of water and nutrients to the tree.
“You can do treatments if you catch it early enough. You can do preventative treatments if you decide to keep the tree,” said Brian Leatherman, district manager for Davey Tree.
Chris Klimas, Mid-Atlantic residential and commercial operations manager of the Davey Tree Expert Co., said treating or removing a tree is an economic decision and that treatment is a commitment of time, energy and resources.
“We have many customers that are doing that, such as Baltimore city,” Klimas said.
The cost for treating and re-treating the trees depends on several factors, according to Klimas, which include the number of trees, the accessibility to the infested population and the size of each tree.
“The larger the density of trees in a community, (it) reduces the costs (of treatment),” Klimas said.
Two-thirds of the cost for treatment comes from the chemical itself, which is very expensive and has one major manufacturer, Klimas said.
According to Harwood, the treatment for these trees is unsustainable.
Treatment involves drilling a hole into the tree and injecting a chemical called ArborMectin and water into the vascular system, Leatherman said. The tree then “pulls up” the product. The treatment will last for two years. After that, the tree will have to be re-treated.
Leatherman said signs of infestation include the heavy presence of woodpeckers, chewed-up leaves in the summer, a D-shaped hole about an eighth of an inch in diameter and an unusually high number of sprouts.
Klimas said infested trees die rapidly, becoming brittle. At that point, the infested tree would have to be removed within six months.
The Emerald Ash Borer, originally from China, was brought to the states, specifically to Michigan, with wood material imported from there, said Klimas. It then arrived in Maryland with plant material coming from Michigan.
“The insects just find a way of hitchhiking cars and trucks,” Klimas said.
Harwood said the Emerald Ash Borers are very good distance fliers. They were originally thought to only fly a few miles.
The strategy used when they first infested a few trees in Prince George’s County was removing a quarantined section of infested trees; the insects would have eventually starved because the next healthy ash tree would be too far away, officials thought.
“It flies far further than we had originally anticipated. It flies up to 18 miles away from its home source,” Harwood said.
Harwood said that when the insects first arrived in Maryland, the situation was “by no means contained.”
The first approach of quarantining the infested trees may have slowed the population growth. Other factors such as weather and the health of the trees may have also slowed the growth down.
Klimas said a strategy for the removal of infested trees could be to manage and schedule the mortality rate over yearly intervals.
Harwood said that a long-term solution for recreating the ash tree population would be using the insects’ native predator, wasps that have been imported from China and are being researched at the University of Maryland.
Leatherman said these trees are needed for the environment and the forest population.
“The beetles (Emerald Ash Borers) are here now, so there’s nothing we can do about that. The effect is the ash population of trees is going to be lost if we don’t treat them,” Leatherman said.