WOOSTER, Ohio — Cutting down ash trees isn’t the only strategy for managing emerald ash borer (EAB) in residential and municipal landscapes.
According to Ohio State University entomologist Dan Herms and Ohio State University Extension educator Joe Boggs, landowners or municipal officials often decide to remove healthy ash trees based on the erroneous belief that this will slow the spread of EAB, which is not correct, or that insecticides are not effective.
“We want property owners and those individuals in charge of making decisions about ash trees in public areas to realize that cutting them down is not the only choice they have,” said Herms.
“The decision to remove ash trees should be founded on sound science.”
He said there are several cost-effective, environmentally sound insecticide treatments that can preserve ash trees through EAB outbreaks.
But not all ash trees should be treated with pesticides, say the experts at OSU and elsewhere.
Rather, treatment methods need to be considered in association with tree inventories. They recommend targeted removal of unhealthy ash trees as part of an integrated management strategy to preserve the integrity and value of urban forests as much as possible.
Valued for their shade, ash trees represent anywhere from 10 percent to 40 percent of all trees in urban areas.
They provide substantial environmental and economic benefits to individuals and communities, including increased property values, lower energy demands, storm water mitigation and storage of greenhouse gases.
An accidental import from Asia discovered in the United States in 2002, EAB has so far killed millions of ash trees in several U.S. states and Canadian provinces.
The insect is predicted to cause an unprecedented $10-$20 billion in losses to urban forests over the next decade.
“We want to emphasize that currently approved treatment protocols for EAB have been rigorously developed, tested and refined by university scientists,” Herms pointed out.
“In many cases, treating ash trees with these insecticides can be both environmentally and economically superior to tree removal when you factor in the ecological benefits of preserving the trees versus the cost of removal and replacement.”
Three systemic insecticides approved by the Environmental Protection Agency have been widely researched for control of EAB: dinotefuran for trunk, bark or soil application; emamectin benzoate for trunk injection; and imidacloprid for soil application or trunk injection.
Insecticide treatment is most appropriate, Herms said, after EAB has been detected within 15 miles, and is most effective when applied before trees are infested.
However, insecticides can also help save ash trees with a low level of EAB infestation.
Spring is the best time for treatment, but in some situations fall treatment can also be effective.