Earlier this week, the Nebraska Department of Agriculture reported that an emerald ash borer was found by the Kearney Park and Recreation Department in a tree in Kearney on a street terrace.
For Todd McCoy and his staff at the Grand Island Park and Recreation Department, they have been preparing for EAB for a while. According to the Nebraska Department of Agriculture, the Kearney EAB sighting was the first find outside of eastern Nebraska. EAB, an invasive beetle that attacks and kills ash trees, was first found in Omaha in 2016.
EAB is a small, metallic-green beetle that is about ½-inch long. The larvae of this wood-boring insect tunnel under the bark of ash trees, disrupting the flow of water and nutrients, ultimately causing the tree to die. EAB-infested ash trees will exhibit thinning or dying branches in the top of the tree, S-shaped larval galleries under bark, D-shaped exit holes and suckers (along the trunk and main branches).
“We have known for a while that it was coming this way,” McCoy said. “We have identified all of our ash trees. The ones of poorer quality, we have slowly been taking them out as we can and replacing those trees.”
McCoy said there are about 200 ash trees remaining in Grand Island parks.
He said the ash tree is a good tree and does well in Grand Island’s climate. McCoy said an inventory of the Grand Island’s urban forest estimated that about 8% of its trees are ash.
“Our dominant tree here is the hackberry,” he said. “We are lucky that we don’t have as many ash trees as some communities, where ash trees may make 30% to 40% of their trees. Those are the communities that will be impacted more drastically than us.”
McCoy said diversification of a community’s urban forest is the key to protecting the inventory. Instead of having a few species of trees dominating an urban forest and being vulnerable to some type of insect or disease, a host of different tree varieties not only increases the aesthetic of a community, but protects the whole of an urban forest from being wiped out by an invading insect or disease.
City has a plan of defense
He said the Grand Island Tree Board recently has completed a plan to deal with EAB in Grand Island.
Barry Burrows, president of the Grand Island Tree Board and city parks superintendent, said the city is required to have an EAB management plan. He said it is not a total plan of action, but gives history, cost estimates and ash tree populations in Grand Island.
Burrows said the last tree population inventory done by the U.S. Forest Service in Grand Island was done in 2010.
He said the 2010 inventory found that Grand Island had a population of ash trees of 1,760 or about 8.3% of the community’s trees.
Burrows agreed that tree species diversification is a key component to a healthy urban forest.
“It just not about diversifying a species, but also diversifying the ages of our trees,” Burrows said. “For instance, we have a lot of old hackberry trees, but we have very few younger ones. Once those older ones start dying, we aren’t going to have as many numbers of the younger ones to take their place.”
According to the U.S. Forest Service, a health and diverse urban forest provides many benefits for a community as they help to filter air and water, control storm water, conserve energy, and provide animal habitat and shade. They add beauty, form and structure to urban design.
Along with disease and insects, urban forest take a pounding from the weather, such heavy winter snows, heavy rains, strong wind storms and drought.
For example, Burrows said June was hot and dry. In yards that have shade trees, the turf is a lot healthier than those yards without shade.
Trees also suffer from the mismanagement of chemicals people apply on their lawns when they don’t follow application instructions.
“If you are going to be a tree in Nebraska, you have to be tough,” Burrows said.
Climate change also is affecting urban forests in Nebraska. When an area experiences few days of extreme cold weather during the winter, that provides an edge to invasive insects, such as EAB, to expand their range. Diversification is also a defense against invasive insect species or diseases that spread because of changing climate conditions.
Grand Island ‘sitting pretty good’
Burrows said Grand Island’s parks are sitting “pretty good” against the EAB threat.
He said the parks department has been proactive about removing ash trees from city parks, especially when EAB was first identified in Nebraska in 2016 in the Omaha area. Burrows said more than 80 have been removed for various reasons.
While attention is focused on EAB, he said there are other borers in the city’s urban forests that are damaging ash trees, but not with the devastating effect that EAB has. Burrows also said last year’s wind storm damaged a number of ash trees that were then removed.
“We are down to about 200 (ash) trees,” he said.
Also, he said, the biggest threat from EAB are not the ash trees in city parks, but those located on private property. While people don’t plant as many ash trees nowadays, Burrows said they were a popular trees in the 1980s and 1990s as “they were one of those trees to take over from the elms back when Dutch elm diseases were destroying that species.”
With the pending arrival of EAB, he said people have backed away from planting ash trees.
Burrows said the biggest concern when an ash tree is damaged and dies is that it becomes very brittle.
“That means potential dangers as the tree can fall over on someone’s car or house,” he said.
He said if homeowners don’t have the funds to take care of the tree or removed, “it becomes a very potential danger.”
Many of the trees that fall because of heavy snow or strong winds are older or damaged trees.
“If I had an ash tree in my yard, I would probably consider removing it sooner than later and start with another tree and get it going,” Burrows said.
Prevent the spread of EAB
The Nebraska EAB Working Group, which includes NDA, the USDA, Nebraska Game and Parks and the Nebraska Forest Services, offers the following suggestions to help prevent the human-assisted spread of the insect:
— Use locally sourced firewood, burning it in the same county where you purchased it, as EAB can easily be moved in firewood.
— Consider treating healthy, high-value ash tress located within a 15-mile radius of a known infestation. Treatment will need to be continually reapplied and will only prolong the tree’s life, not save it. Trees that are experiencing declining health should be considered for removal.
— If you are in a non-infested county and think you have located an EAB infestation, please report it to the Nebraska Department of Agriculture at 402-471-2351, the Nebraska Forest Service at 402-472-2944 or your local USDA office at 402-434-2345.