When news first broke last week that the emerald ash borer, a deadly tree pest, had been found in the Omaha metro, Daryl and Cathy Greger struggled to figure a way forward.
The Ralston couple have two ash trees, one in front, one in back. And the big shady one in back? It’s like an extension of their home.
“We eat out there,” Daryl Greger said, “we read the paper out there, watch TV out there sometimes.”
Should they cut the trees down? Treat them?
“I was thinking, ‘Oh, we’ve got to do (something), we’ve got to call somebody. Who? How? Where?’ ” Greger said.
Then they got answers at a University of Nebraska-Lincoln Extension workshop on the emerald ash borer.
“We know what we need to move forward,” Greger said. The couple have chosen to hire an arborist.
Even though the borer is expected to wipe out most of the area’s thousands of ash trees in the next 10 to 20 years, homeowners have time to take a deep breath before deciding whether to treat their ash trees or have them removed, tree experts say.
In other words, put the wallet away and pause. Why?
The borer’s life cycle is too far along this year to be killed by homeowner-administered chemicals now. Professionally applied chemicals will still work, but with each passing month this summer, the effectiveness of starting those treatments will decline.
You can wait until spring 2017. The chances your tree will be mortally affected by ash borers before next spring are slim.
“There’s really no reason to panic,” said John Fech of the Nebraska Extension Services of Douglas and Sarpy Counties.
The borer has been found in Pulaski Park, near 49th Avenue and G Streets. Friday, the Nebraska Department of Agriculture confirmed an emerald ash borer in a tree on private property in Greenwood in Cass County. State Ag Director Greg Ibach said more awareness by homeowners will lead to additional finds.
Still, Ibach said a quarantine covering Douglas, Sarpy, Cass, Washington and Dodge Counties regulating the movement of ash nursery stock, firewood and mulch should slow the spread of the beetle, “giving homeowners and municipalities additional time to consider their options and make decisions about the future of their ash trees.”
A local nurseryman and a state forester urged homeowners to think before launching into treatments. They say people who treat their ashes must realize that doing so is just delaying the inevitable. Even treated trees are expected to eventually succumb to disease or injury prematurely because of the stress of treatment.
Ask yourself whether you’re willing to pay to treat a tree for years, knowing that you won’t be able to save it, said Dan Mulhall, vice president of Mulhall’s Landscaping, Nursery and Garden Center.
Cities such as Omaha, Council Bluffs and Lincoln don’t have the luxury that homeowners have to wait another year to take action. The cities have begun treatment and removal programs. With so many trees to manage — the City of Omaha has about 11,000 ash trees in parks and on rights of way — the city must try to spread out its costs by treating and removing trees systematically.
The city, like professionals, has access to more effective chemicals than homeowners can buy, and these chemicals, which are injected, can be administered in the summer.
Brook Bench, Omaha Parks and Recreation director, agreed that eventually most of the city’s ashes will succumb to the borer. And he urged Omahans to be mindful that the injection treatment can stress the trees.
However, he said, it’s in the city’s best interest to preserve some public trees by using an injection treatment and to cut down any that are damaged, unhealthy or too old or too young.
Bench said the city would treat about 5,000 of its ash trees. An example of those worth treating: those that line Abbott Drive.
Eric Berg, community forestry and sustainable landscapes program leader for the Nebraska Forest Service, agrees that ash trees are doomed. He urged ash tree owners to plan now for a tree’s death, which could lead to an expensive removal.
And, he said, plant a replacement tree soon, while you still have 10 to 15 years before your ash is gone. There’s no rush, because summer heat stresses new plantings. Wait until fall, an ideal time to plant trees.
“The key is diversity,’’ said Berg. He suggested Kentucky coffeetree, northern catalpa, hackberry and oak.
Mulhall agreed that homeowners would be wise to plant a replacement tree now.
“Trees should be planted for the next generation,’’ he said, “and the next generation won’t be using ash trees.”
Features to look for in identifying an ash tree
Seeds: Paddle-shaped. Only female trees produce seeds. Seeds are usually not produced every year.
Leaves: Ash leaves are divided into leaflets, usually five, seven, nine or 11 leaflets per leaf. This is called “pinnately compound.” To know whether you are looking at a leaf or a leaflet, look for the buds: A bud is usually present along the twig at the base of the leaf just above where the leaf attaches to the twig. No bud is found at the base of a leaflet.
Buds: Occur in pairs on the twigs. This is known as “opposite” arrangement. The leaves and twigs also occur in pairs (opposite from each other).
Ash flower gall: This is an infestation by a tiny mite, which causes these unsightly galls to develop. It’s found on the seedless cultivars (male trees). These galls often serve as an identification feature for ash trees.
Bark: As ash bark matures, it splits into diamond-shaped fissures. It is fairly distinct in this photo, but does not always appear this way. The base of the trunk has the most mature bark so is a good place to look for this feature.
Fall color: Green ash is usually yellow, white ash often maroon, sometimes with yellow in interior. Autumn purple ash is a cultivar of white ash.
Forest specialist answers questions about ashes, borers
With the discovery of emerald ash borer in Omaha, some confusion over treatments has arisen. Here are clarifications to some commonly asked questions:
“Has the emerald ash borer been found in other areas of Nebraska?”
As of June 13, 2016, it has been confirmed only in southeast Nebraska (in South Omaha’s Pulaski Park). It is possible that this type of borer is present elsewhere in the state but has not been detected.
There are other types of borers that attack ash, particularly trees that are under stress or in decline. The 2012 drought was particularly hard on ash trees, and many are infested with these native borers.
“What is the 15-mile treatment consideration zone?”
Ash trees within 15 miles of an identified infestation of emerald ash borers are at higher risk for attack. Residents in a 15-mile zone may want to consider timely treatments of high-value trees in good condition. For the most recent zone, go to nfs.unl.edu/nebraska-eab.
Outside such zones, trees are at a lower risk, especially if they are being well cared for. Treating trees outside a 15-mile zone provides little or no benefit to the trees, yet exposes humans and the environment to pesticides, wastes money and — in the case of trunk injections — causes needless tree damage.
“How do treatments work?”
Insecticides used against emerald ash borer move under the bark through the tree’s water-conducting system to leaves and branches, where the insects are feeding. Two stages of the insect are targeted: the adult beetles and the young larvae.
Adult beetles typically emerge and feed on leaves in mid- to late May. Control of adults reduces the number of eggs they produce.
Larvae hatch from eggs and begin tunneling under the bark in June. Young larvae are susceptible to insecticides but become tougher to kill as they grow older. Their tunnels disrupt the movement of the pesticide within the tree, resulting in poor control if treatments are made too late in the season.
“Is it too late to treat this year?”
For homeowner-applied soil applications, the time for treatment has passed, which is early to mid-spring, depending on the insecticide used. Soil applications require several weeks for the roots to pick up the chemical and distribute it throughout the canopy of the tree. If applied now, by the time the chemical reaches the top of the tree, few adult beetles will be present and the larvae will be much more difficult to kill.
Professional trunk-injected chemicals move more quickly; however, the ideal time to apply them, too, has passed (mid-May to early June). Treating now will yield partial control but the effect will decline as summer progresses.
“What is the cost of treatments?”
For a 20-inch diameter tree, costs average about $100 per year for professional treatments. Trees will need to be retreated every one to two years. Homeowner-applied soil treatments cost about $50 per year and also need to be redone once a year for the life of the tree. When most ash trees are gone and the population of the emerald ash borer has dropped, it may be possible to reduce the frequency of treatments.
“What are the drawbacks to treatments?”
All treatments need to be repeated every one to two years for many years to come.
Trunk injections greatly reduce the chance of exposing non-target organisms to the toxic chemical and can better protect larger trees, but a major drawback is the internal damage done to the trunk. Damage occurs from the holes made in the trunk and from the pesticide itself. Several injection methods and chemicals are available, but in general the larger the holes and the more chemical injected, the greater the damage. Cumulative damage will shorten the life of the tree, even if emerald ash borers are controlled.
Soil treatments should not be used near sources of water or in areas with flowering plants, which could transmit the chemical to bees, butterflies and other pollinators. In addition, soil treatments often do not adequately protect trees, especially those over 15 inches in trunk diameter.
“Is my tree a good candidate for treatment?”
Be very selective about the trees you treat. Prominent trees in the landscape or trees that provide shade to the home are more valuable and may be worth treating. Trees under wires or too close to sidewalks or buildings generally should be removed rather than treated.
Trees in good condition will respond better to treatments and will better handle the damage that some treatments cause. Examine your trees for thin foliage, dead branches, sucker sprouts along the trunk or major limbs, decay mushrooms, borer holes and damaged or missing bark caused by mowers or string trimmers. Trees with these problems are probably stressed or in poor health and would not be good candidates for treatment.
Contact a certified arborist to examine your tree and discuss options. Both treatments and removals are best done by a professional with the proper training and experience.
Removal costs can be high, but if your tree is in poor condition or you decide not to treat, it will eventually need to be removed. As ash trees disappear with the spread of emerald ash borer, replanting now will allow a new canopy to become established to provide the beauty, shade and economic benefits that we all enjoy from our trees today.
Contact the writer: Laurie Stepanek, Nebraska Forest Service, nfs.unl.edu/nebraska-eab
What to consider if you own an ash tree
If you have an ash tree in your yard, here’s what the University of Nebraska-Lincoln Extension and Nebraska Forest Service advise.
Think through your options.
» Make sure your tree is an ash and not a look-alike, such as a box elder maple.
» Evaluate your tree to see if it’s healthy enough for treatment. Ash trees have suffered from a variety of assaults, including drought and other borers. Look for defects and cracks. If more than one-third of its leaves are missing, it may not be worth saving. Trees that are located in a poor spot, such as near electrical wires or too close to a house, also should be cut down rather than saved. If the tree is young, replace it now rather than investing in it, because its lifespan will be shortened.
» Inspect your tree for signs of the emerald ash borer. Look for leaf die-off in the upper canopy; tiny, D-shaped exit holes in the bark; the beetle itself; and the presence of woodpeckers. If your tree has symptoms, have a certified arborist examine it.
» Consider your reasons to prolong the tree’s life. Reasons can include: It’s healthy and it provides energy-saving shade, it enhances the aesthetics of your yard or you have a personal attachment.
» Determine whether you’ll treat the tree or hire someone. If your tree is under 20 inches in diameter at chest height, you can treat it yourself with the ground drench. These are most effective when used between April 1 and May 15. If the tree is bigger in diameter, hire a certified arborist to treat the tree with an injection method. This can still be done, but with each passing summer month, initiating treatment becomes less effective. Recognize that treatment will be required for the life of the tree. Some treatments must be done annually, while others can be done every two years. If you decide to treat the tree, it’s better to start while the tree is still healthy rather than waiting for the borer to strike. However, a mildly infested tree can recover with proper treatment.
If you’re not going to treat the tree, then what?
» Think through your removal options. You may be able to gamble on the borer’s not arriving at your neighborhood for several years, but if you wait, you may pay more for removal. Ash tree deaths are expected to explode once the infestation reaches full strength. If you have your tree cut down before the ash borer causes widespread mortality, removal costs may be less. Waiting until the tree dies is not prudent. Unlike some species that are sturdy even in death, ash trees become brittle and dangerous within about two years of dying.
» Hire a certified, licensed and insured arborist. Get at least two estimates, ask for references and insurance information.
Plant a replacement tree.
Get a tree in the ground so that it is established by the time you lose your ash. Foresters hope you’ll plant a hardy, long-lived shade tree. Consider touring the Omaha Public Power District’s arboretum at 108th and Blondo Streets to view a healthy selection of trees.
Resources for ash tree owners
Certified arborists? Search the Nebraska Arborists Association website, nearborists.org/search_for_arborist or the International Society of Arboriculture at isa-arbor.com/findanarborist/arboristsearch.aspx
Treating yourself? Online, go to extension.unl.edu/statewide/douglas-sarpy/
By phone, call the extension service in Douglas-Sarpy Counties at 402-444-7804 or the USDA Hotline at 866-322-4512.
Attend a workshop. One is scheduled Wednesday from 9:30 to 11 a.m. at 8015 West Center Road. It costs $20 per person or couple sharing materials.
Planting a new tree? retreenebraska.unl.edu/
Jay Withrow contributed to this report.