By John Kmitta
Tree care professionals, homeowners and municipalities faced with Emerald Ash Borer (EAB) infestation have not only had to battle the pest, but also misinformation. In many cases, people have thought that nothing could be done to control the pest; or they have thrown good money after bad by not understanding the pest, community policies or both. However, effective and predictable management strategies have emerged as scientists have continued to refine application techniques and treatment protocols. When insecticides are applied according to these newer protocols, results demonstrate that several products can effectively protect ash trees even when subjected to peak EAB populations. These new management options and informed control strategies are showing that treatments work, and are a viable option for preserving the economic and environmental benefits that trees provide. Depending on the situation for municipalities, treatment of high-value trees can be as, or more, cost-effective than tree removal. Working with a reputable tree health care distributor, and developing a proper plan can meet the needs of your clients and the community as a whole.
The current state of EAB
“Emerald Ash Borer continues its spread throughout states currently infested with EAB, and was also recently detected in Iowa — raising the total number of states with confirmed infestations to 13,” said Shawn Bernick, director of research and technical support at Rainbow Treecare Scientific Advancements.
According to Chip Doolittle, president of ArborSystems, the outbreaks in Iowa are more sporadic due to the fact that EAB is now moving into the plains states, and there are a lot of cornfields and open spaces between groves of ash trees.
This past year, EAB has been identified in the Minneapolis-St. Paul area, as well as in southern Wisconsin, Missouri, north-central Kentucky, West Virginia, Pennsylvania and Washington, D.C., said Jim Rollins, Midwest regional sales representative at Mauget.
“It continues to spread in all directions,” said Rollins. “One trend I’ve noticed is that it tends to follow the major highways, which tells me that it is catching a ride on cars or trucks, or being spread via firewood or on nursery stock.”
“EAB has the ability to survive in dead wood — notably firewood — for an extended period of time,” said Rob Gorden, director of national sales for Arborjet. “This dormancy, known as estivation, typically occurs from late fall through early spring, when it can be easily spread in firewood.”
Said Bernick, “Forecasting how quickly EAB will spread into a given area is challenging, because it is virtually impossible to predict where and when infested firewood will be transported to the next new location.”
According to Gorden, many states are actively searching for EAB using traps and trained early detectors. Most new finds continue to show evidence of being in the trees for several years before discovery. New finds increase each year during adult flight, when the insects are both more visible, and more likely to become entangled in traps.
“EAB tends to move in waves,” said Doolittle. “Pests infest a region, and when all the ash are dead or treated, [EABs] move on or die out. If you treat trees proactively, or even when early signs of infestations are noticed, you can protect and save the trees.”
According to Bernick, research continues to be aimed at better understanding the biology and life-cycle behaviors of EAB. In addition, several research projects are being conducted to develop improved detection and surveying methods, and better understand the impacts of EAB on different ash species.
“While not all insecticides labeled for EAB have shown acceptable levels of protection, scientists have found that when specific management protocols are followed, multiple insecticide options are available that can be used to protect and preserve high-value ash trees,” said Bernick.
According to Rollins, as more is learned about the insect and its life cycle, and as more is learned about the various treatments available, management programs are able to be fine-tuned for better results and more efficient control of this insect.
“Preventative maintenance is the key,” said Dr. Joe Chamberlin, field development manager, southeast, for Valent Professional Products. “How preventative? Nobody can tell.”
“Upon entering a tree, EAB begins to feed and damage the vascular system undetected,” said Gorden. “Its damage is often invisible for two or more years. By the time that damage is evident, the pest is well on its way to killing the tree. Experience has demonstrated that preventative treatments afford the greatest chance of reducing damage and saving the tree.”
According to Chamberlin, it is recommended that once EAB is spotted within 10 to 15 miles that you should begin preventative treatments. “However, just because it was spotted within 10 to 15 miles, does not mean that your tree is not already infested with EAB,” he added.
Bernick points out that one of the biggest challenges to managing EAB is determining exactly where EAB is located.
“EAB is extremely difficult to detect when its population levels are low,” said Bernick. “We also know that the likelihood for success with insecticides increases significantly if trees are treated prior to being infested. Given these two challenges, it makes it difficult to recommend treatments solely based on a specific distance to a known infestation. Fifteen to 20 miles from the nearest infestation is good guideline, but it is only a guideline.”
“Arborists are the front line of defense,” said Rollins. “Make sure that you are well educated as to what to look for in terms of damage. When you are out and about, keep an eye on ash trees. If you seen anything that looks like damage, investigate further, and then it might be time to begin preventative treatments.”
Bernick recommends determining the value of the tree to the client or city. “The value of the tree must then be weighed against the relative risk of the tree being infested with EAB and the cost of doing the treatments,” he said. “The closer you are to an infestation, the greater your risk is to losing a tree from EAB.
“Not all trees can or should be treated, so it is important for commercial arborists to work with clients to identify which trees provide the most benefit to them,” he added. “A municipality must prioritize candidate trees for treatment as well.”
“Research has improved our ability to effectively manage EAB,” said Bernick. “EAB insecticide recommendations continue to change as new research comes in. Soil-applied insecticides are commonly used by tree care professionals to manage many keys pests, and can be effective against EAB when used correctly.”
According to Gorden, applicators should be aware that soil-applied products may require several weeks for absorption from the soil into the roots for effective protection within the tree. This limits the use of those treatments to the spring when EAB larvae begin damaging the tree’s vascular tissue. “Trunk-injected treatments aren’t introduced slowly to a tree, as they are placed and sealed directly into the trunk through the tree’s vascular system,” Gorden added.
However, homeowners are limited to purchasing soil drench products, applied once annually, said Gorden. Research indicates that once EAB begins to attack, a second annual soil application is required to save their trees. When this point is reached, the only legal way to treat by soil drenching is to contact a certified applicator to make these treatments, he stated.
According to Doolittle, trunk injection that does not require drilling to apply the chemical is beneficial option — especially when treating already infested trees.
According to Chamberlin, some chemicals for control of EAB are now labeled for basal bark application, which is a more holistic approach to tree care. The chemical is applied from soil level up to breast height up to the point of runoff around the circumference of the tree. It works out to a couple fluid ounces of product per inch of diameter at breast height. The highly soluble molecules absorb quickly into the xylem for uptake.
“The speed of uptake with basal bark spray is comparable to soil injection or trunk injection treatments, but the applicator does not need specialized equipment and can visibly monitor the proper amount of product to apply,” said Chamberlin.
According to Gorden, when selecting an application method, considerations should include ease of application, proximity to environmentally sensitive areas, available soil areas, insecticide runoff potential, effective residuals, and length of control of the product.
“There are certain philosophies or strategies for preventative treatments, and other strategies for when the pest is firmly entrenched in the area,” said Rollins. “It also depends on the size of the tree being treated. Treatments are different for small trees versus larger, more established trees.”
According to Rollins, there is a lot of good information available on the Internet, through local extension services, and through local ISA chapters.
“Get all of that information, and make your decisions based on the data, the type of trees you are dealing with, and the level of infestation in your area,” he said.
Keys for homeowners and municipalities
Doolittle said that the message to homeowners and municipalities is that, “Emerald Ash Borers are not the end of the world. EAB can be managed without the drastic measure of cutting down trees that resulted in tens of thousands of healthy trees being cut down unnecessarily. These pests can be controlled, and ash tress can be saved, both preventatively and curatively, with proper chemical treatment.”
According to Gorden, since EAB only feeds and reproduces on ash trees, scientists believe that as the EAB wave reaches a city, it will kill all unprotected trees while protected trees remain untouched.
“When the unprotected trees begin to die, they are no longer suitable for EAB reproduction, and the EAB population will begin to fall, reaching significantly lower levels in the community,” said Gorden. “Treatment will not be required at intense and frequent levels indefinitely.”
Bernick offers several messages to homeowners and municipalities regarding EAB. Homeowners should be urged not to transport firewood, and to burn it where they buy it. They should work with a Certified Arborist to create a plan for their ash trees, and — if treating their own trees — homeowners should use products that are effective for the size of the tree being treated.
Municipalities should create an EAB management plan, and revisit the plan as new research comes in so that the necessary changes can be made. Also, municipalities should identify how the city will pay for management of EAB (limited Federal and State funding is available to local governments for the management of EAB).
“Treatments are effective when applied according to specific protocols,” said Bernick. He added that, “The economics of treating municipal trees have changed dramatically over the past four years. Treatment can be a cost-effective option for a city and result in preserving the economic and environmental benefits that urban trees provide communities.”
Gorden agrees; “Treatment is now an effective means of protecting trees, and is far less costly — even in the long run — than removing trees. Even without adding in all the indirect costs associated with tree loss, treatment will effectively preserve tree while costing less.
According to Chamberlin, for municipalities it is often a matter of economics, but for homeowners, saving an ash tree might have personal meaning. “Perhaps they grew up with that tree, used to swing from that tree, etc.,” he said. “For a municipality, it is a different dynamic economically. A standard street tree out in the open might only cost a few hundred dollars to remove, but a tree near a house, power lines or other structure can be much more expensive.”
“Systematic and preemptive removal of these urban trees will not solve the problem, but instead, create a new set of problems including increases in heating and cooling costs, storm water runoff, and urban flooding, as well as neighborhood and property value decreases,” Gorden added.
But according to Bernick, an effective municipal EAB management strategy will utilize a variety of practices including tree removal, replacement with non-ash species, insecticide treatment and, in some cases, letting nature take its course.
“Prioritize which trees will receive treatment and recognize that not all trees are good candidates for treatment,” he said.
Rollins tells homeowners and municipalities to be proactive and have plans in place and ready to implement. “You don’t want to wait until that tree is half dead before you begin a treatment program,” he said.
The “take-home” message
“The take-home message is that you can’t assume that if the tree isn’t showing symptoms that it isn’t infested,” said Chamberlin. “Once the tree reaches 40 percent dieback, about the only option is to cut it down.”
Said Doolittle, “I think the main take-home is that arborists need to be aware that usually when they find the larvae, the insect has already been there for at least two years. That means they should be preventing this well in advance of the wave.”
According to Bernick, diagnosis of EAB can be challenging, especially in the earliest stages of an infestation.
“Symptoms of EAB can easily be confused with drought or other abiotic stress and damage from native wood borers,” he said. “Also D-shaped exit holes are not readily apparent at eye level on trees that are in the earliest stages of infestation. University Extension services and state and federal government agencies have produced great EAB fact sheets to help practitioners diagnose the signs and symptoms of EAB. Reference these and have them handy when you are in the field.”
Bernick also urges arborists to follow the proper application protocols. “Ensure that products are applied at the proper time, using the correct dosage rate and application technique,” he said. “Treating trees before they are infested and showing visible symptoms will increase your likelihood for success.”
“Be proactive,” said Gorden. “Preventative and early treatment of trees infested with EAB provides the best results for saving the tree.”
According to Gorden, if a tree is undersized, physically damaged, or infested beyond treatment options, plan for its removal and replacement. However, as stated earlier, the cost of citywide removal is financially and environmentally devastating to the community as well.
“Both public and private tree health care professionals must remain attuned to the new research and new information on controlling EAB,” said Gorden. “Because new research is generated every year, data from the earliest outbreaks is simply ineffective at making treatment decisions. Check with surrounding cities that have made both effective and less successful choices at preserving their urban forests. Evaluate their results and ask for their guidance.”
The future of EAB
According to Bernick, EAB will continue to spread short distances via natural spread of the beetle, and will continue to spread long distances on firewood. Detections in new states will most likely be more localized initially and spread outward via natural flight and movement of firewood. Until detection techniques improve, we will be challenged to know exactly where EAB is located when population densities are low.
“Unfortunately it does not look good for native ash trees, and it is only a matter of time before EAB spreads across the country to areas where native ash trees are present,” Bernick added. “Hopefully science can continue to develop new and improved management tools, and long-distance spread through firewood can be minimized.”
“Chicago and Columbus are where Detroit was in 2002 [with regard to infestation],” said Chamberlin. “How close are these cities to massive devastation? The suspicion is that they’re real close.”
Dr. Frederic Miller of Joliet (Ill.) Junior College and the Morton Arboretum, said that some municipalities, which are heavily ash, could lose a third of their tree canopy due to EAB if left untreated.
According to Gorden, evidence suggests that EAB has been hidden for several years in many of the locations it now occupies.
“Each newly attacked tree, which serves as a reproductive site, will enable new adults to spread across towns each summer, which has lead the USDA-APHIS to determine that it is not possible to stop the spread of EAB,” said Gorden. “However it is possible to slow the spread through quarantines, effective treatment and reduced movement of firewood.
“There is a strong likelihood that every town and citizen with ash trees will face this serious threat sooner than later,” Gorden added. “History has shown that effective planning can take up to two years — including tree inventories, stakeholder meetings, budgetary planning and the proper training of applicators. If you haven’t started this planning process, meetings and compilation of current data should begin immediately. The best chance for a successful outcome with healthy trees is to prepare and begin treatment before EAB arrives.
“Seek the support of professionals with experience in all control strategies, and also chose someone who can assist in bringing the necessary science and cost information to your elected officials,” he said. “No one wants to spend any extra money during tight financial times, but with proper preparation, you will save your ash trees and still save your budgets.”
Added Rollins, “With some of the research we have done and some of the plans and programs that have been put in place, we are able to slow down the spread of the insect. Even though we can’t completely stop EAB at this point, we can identify those trees that are important to us and develop programs where we can save those trees and keep them healthy for many years to come.”
Said Miller, “If you want to keep ash trees, you’re going to have to look at chemical control.”
Control Options for EAB
TREE-age insecticide is a unique chemistry, not available in any other formulation for tree injection use. It is designed to be injected directly into the vascular system of the tree. It has been shown TREE-age will provide two years of protection from Emerald Ash Borer from a single injection. For more information, visit www.arborjet.com
ArborSystems Wedgle Direct-Inject system is a trunk injection treatment option that does not require drilling to apply the chemical. Direct-Inject treatments place chemical into the cambial zone where it can be most quickly and efficiently used by the tree. For more information, visit www.ArborSystems.com
Imicide offers preventative control of EAB, and Inject-A-cide B is an in-season curative option. Mauget will soon be launching a new formulation of Imicide, which has proven to have improved water compatibility for better distribution and faster uptake. For more information, visit www.mauget.com
Rainbow Treecare Scientific Advancements
Xytect 75WSP is a broad spectrum, systemic insecticide that utilizes the proven performance of imidacloprid and provides season-long control of a wide variety of insect pests including Emerald Ash Borer. Xytect 2F is a broad spectrum, easy-to-use, highly concentrated systemic insecticide and provides 12 months of protection. Xytect Infusible is used with the M3 Micro injection system. It is trunk injected to kill active borers, or for use where soil application is not an option. For more information, visit www.treecarescience.com
Valent Professional Products
Safari Insecticide from Valent Professional Products can be applied as a basal trunk spray, a soil injection or a soil drench for control of EAB (approved for use in all states except California and New York). Data from university trials show that efficacious concentrations of the active ingredient in Safari (dinotefuran) are present in ash tree foliage as little as 21 days after a soil application or basal trunk spray. For more information, visit www.valentpro.com/safari