Emerald Ash Borer:
Forever Changing the United States
Photo courtesy of Michigan State University and http://www.emeraldashborer.info/photos.cfm
Author: Jay Seaton
Course: Invasive Pests and International Trade, ENTO 496
Instructors: Dr. John Foster, Dr. Ousmane Youm, and Ms. Kate Kneeland
December 7, 2009
The emerald ash borer, Agrilus planipennis (Fairmaire), is a relatively new and very devastating pest that is threatening native ash trees in the United States. It is estimated that over 50 million ash trees have already fell victim to this pest (GPI, 2009). The pattern in which emerald ash borer is following is eerily similar to that of the Dutch elm disease which spread across North America and destroyed most of the native elms from America's forest and front yards. Since it was first identified in 2002 in southeast Michigan, the spread of emerald ash borer has been rapid. It is now found and confirmed in 13 states and southwest Ontario, Canada and is showing no signs of stopping (USDA-APHIS, 2009). Emerald ash borer will drastically change the ecological and economical landscape of the United States in both our natural and urban environment. It is imperative to bring awareness to the problem and understand the variety of issues and indirect results involved with a widespread infestation of emerald ash borer.
History and Biology
When dealing with any invasive pest and developing an integrated pest management plan, it is crucial to gather as much information as possible related to the biology of the pest. One of the greatest challenges with emerald ash borer was the overall lack of information. Very little literature in relation to the emerald ash borer existed before 2002. There was only 2 short papers in existence in regards to emerald ash borer: Chinese Academy of Science (1986) and Yu (1992) (USDA-APHIS, 2009). In dealing with emerald ash borer, most of the research has been done in the last decade, since it has invaded the United States and Canada.
What is known for sure is that emerald ash borer is native to Asia. It originates in many provinces of China, Japan, Korea, Taiwan and along the neighboring borders of Mongolia and Russia (USDA-APHIS, 2009). It is speculated that emerald ash borer arrived in the Detroit, Michigan area in wooden packing materials shipped from Asia sometime in the 1990s. Some in the scientific community believe that it may have been in southeast Michigan for 12 years before it was identified as the cause of the decline of ash trees in the area. In 2002, the United States Department of Agriculture officially identified the emerald ash borer (USDA-APHIS, 2008).
Initially there were 5 counties in the Detroit, Michigan area found to be infested with the emerald ash borer and all were quarantined. Now the quarantine efforts have grown to include the entire State of Ohio, Indiana, Illinois and the entire Lower Peninsula of Michigan. It is because of the now illegal movement of ash nursery stock and firewood from quarantined areas, that there is also selected areas quarantined in the Upper Peninsula of Michigan, New York, Maryland, West Virginia, Virginia, Kentucky, Missouri, Minnesota, Wisconsin, Pennsylvania and Ontario, Canada (USDA-APHIS, 2009).
The emerald ash borer is a small, 1/2 inch long and 1/8 inch wide and metallic green in color. The abdomen under the wings is purple. The larvae are legless and white in color, with body segments that are bell shaped and flattened. The ash trees that are infested will begin to die first in the top 1/3 of the tree. In response to the infestation, the tree will sprout shoots and leaves from the base (USDA-APHIS, 2009).
Emerald ash borer will usually complete its life cycle within one year, but in much colder climates will have a 2 year life cycle. The female will lay between 1 to 20 eggs at a time, preferring to lay her eggs in the cracks on the surface of the bark or just under the outer bark of ash trees. A female can on average lay between 60 to 90 eggs in her lifetime. Eggs will hatch between 7 to 10 days into small larvae that will bore into the bark and begin to feed on the cambium (layer of tissue that creates the outer cells (phloem) and the inner cells (xylem), these cells are responsible for carrying water and nutrients between the roots and the leaves). It is because of the larvae feeding on the cambium that result in the death of the ash tree. As the larvae continue to grow, going through 4 instars before pupating, they create S-shaped galleries as they tunnel and feed. They will continually feed through the summer and fall, then construct an overwintering chamber and will emerge as adults the following spring. They will excavate a D-shaped hole to emerge from the tree. Upon exiting the tree, they will begin to feed, usually on ash tree leaves, for around 3 weeks before they begin to mate. The damage caused by the adults feeding on the live foliage is minimal. 7 to 9 days after mating, the females will lay their eggs. Females will mate up to 3 times in their life time. Males will on average live for 13 days, while the females will live for an average of 22 days. They can fly anywhere from 1/2 mile to 5 miles to find a suitable tree to lay their eggs, but very rarely do they fly much over 1/2 mile. Ash trees will be continually infested until they are completely devoid of nutrients (USDA-APHIS, 2009).
As stated above, it is the larvae feeding on the cambium of the tree that is the cause of the death of ash trees. The continually infestation of ash trees and the feeding of the larvae throughout the summer and fall will severely interrupt the natural process of the tree and eventually kill the tree. One of the main reasons of concern is that emerald ash borer infests any age of ash tree of any health condition. It has been found in ash trees as small as 1 inch in diameter. Not only stressed trees are attack, but healthy trees are susceptible as well. Once a tree is infested, death will usually occur within 1 to 5 years (USDA-APHIS, 2008).
The spread of the emerald ash borer is not only done by natural means, but by man too. The quickness and erratic spread has been done by the transportation of invested wood, mainly firewood. As seen on the most recent emerald ash borer location map, the quarantined areas are strange in location. Maryland and Virginia both were invaded by the illegal movement of infested nursery stock (USDA-APHIS, 2009). Missouri, Minnesota and Wisconsin are thought to be infested by the transportation of firewood. It is because of this that efforts to contain emerald ash borer have centered on the preventing of movement of firewood and ash nursery stock by quarantining areas that are known to have an infestation. Emerald ash borer has greatly affected the nursery, timber, recreation and landscaping industry as well as the natural landscape.
Ecological and Economic Impact of the Emerald Ash Borer Invasion
The Value of Ash Trees
According to the United States Forest Service there are an estimated 8 billion native ash trees in the United States' forest and woodland areas. The native ash that are being attacked are green ash (Fraxinus pennsylvanica), white ash (Fraxinus americana), black ash (Fraxinus nigra) and blue ash (Fraxinus quadrangulata). They account for an estimated 5.5 percent of all tree species found in the northeastern United States. In parts of the Midwest, ash comprises 20 percent to 40 percent of the forest ecosystem (USDA-APHIS, 2009). Of the 8 billion native ash trees in the United States, all of them are at risk of being eliminated because of the emerald ash borer. Should nothing be done to prevent the spread of this pest, all of these native ash trees will be destroyed. This will trigger a drastic change in the species composition of our native woodlands.
Ash has many commercial uses, for years it has been harvested to be used as firewood, furniture, packing material, paper, pulp and cabinetry. Due to the wood properties of ash, it has been a staple of the tool handle and baseball bat industry for years. In the eastern forest of the United States there is 114 million board feet of ash harvested for saw timber, creating a value of $25.1 billion. The nursery industry in the United States produces 2 million ash trees annually. The nursery crop is valued at $100 to $140 million based on the value of the trees being $50 to $70 per tree. Emerald ash borer has the unique opportunity to completely and forever remove a billion dollar industry from the eastern United States (USDA-APHIS, 2009).
A total removal of ash trees from our urban and natural environments will directly and indirectly affect the international trade between the United States and its foreign partners. In 2008, the United States exported 11 percent of the total volume of sawn hardwood, just under 2.0 million cubic meters of hardwood logs (UNECE, 2009). With the threat of invasive pests and with the potential of shipping infested products, ash will be removed from the exported lumber, causing a direct affect on the timber industry. There will also be an increase in imported logs to replace the ash trees that once sustain the nation's market.
Currently in the United States, it is estimated that invasive species cost $137 billion dollars per year (USFS, 2003). This only quantifies the direct cost of controlling invasive species, but not the cultural and ecological importance of losing native species because of invasive pests. One thing to consider is should the emerald ash borer eliminate all ash trees in our forestland, what will grow in its place? Exotic, invasive species, like saltcedar, Russian olive, mimosa, Siberian elm and tree of heaven are all aggressive trees that could expand their range should the ash be eliminated. This is a great concern because it would be a tragic change in the makeup of the native woodlands and would increase the annual cost of controlling invasive species.
Ash is also of moderate importance to wildlife, the seeds being primarily eaten by small mammals and birds. Should the United State lose all ash trees, a common food source for wildlife is will be lost. Approximately 46 percent of all threatened and endangered plant and animal species are impacted by invasive species (USFS, 2003). Emerald ash borer will affect many of these by drastically changing their natural habitat and food source. It is difficult to estimate, but it is a startling possibility that without the presence of native ash and the continuing spread of other invasive tree species, many native plant and animal species will join the federal threatened and endangered species list as a direct result of the emerald ash borer.
The United States Forest Service in FY 2008 had a wildfire suppression budget of approximately $1.4 billion dollars (Abt, 2009). This budget over the past several years has continued to grow as the threat of wildfire has loomed across the nation. In 2008 there was 5.2 million acres of wildland burned and in 2009 there was 5.6 million acres burned (NIFC, 2009). Should emerald ash borer leave the 8 billion native ash tree dead in the forest, how will that affect the wildland fire suppression budget in the United State? By changing the fuel load of the eastern forest, this will greatly increase the potential for wildfires to ravage the natural landscape.
The potential of wildfires as a result of the emerald ash borer infestation have many direct and indirect effects that can forever change the lives and landscape of the eastern United States. These indirect effects are difficult to quantify and can make the overall cost of a wildfire 10 to 50 times that of the suppression cost (Zybach, 2009). There is the health risk from the oncoming fires, property damage, soil erosion and water quality issues. Wildfires also have a direct effect on the topic of global warming and CO2 emissions. Wildfires can interrupt travel, both ground and air transportation, cause mass power outages due to burned transmission lines and delay in energy production. Not to mention the loss in the recreational opportunities and the aesthetics associated with the eastern forest ecosystem. The heritage and the history of the east lay in the heart of the forest and are at risk of being lost due to the increased chance of wildfires. All of this is a very real scenario should emerald ash borer continue its reign of destruction.
In the Kansas and Nebraska communities, it is estimated that on average, ash comprises 25 to 35 percent of the total trees. In some areas of North Dakota, communities' total tree resources are made up of an average of 60 percent ash (GPI, 2009). In a survey conducted in Chicago, it was found that 19.2 percent of the public trees were found to be ash (IEABRT, 2006). In Wisconsin there are 5 million ash trees found in communities throughout the state, an estimated 20 percent of all urban trees (State of Wisconsin, 2008). The affect of emerald ash borer completely removing ash from the urban landscape is that 0.5 to 2 percent of the total leaf area is lost (USDA-APHIS, 2009).
When thinking about energy savings, properly placed trees can save the average home owner money in the short and long run. The average savings by planting a tree to help in heating cost and to shade your cooling unit and windows can give a home owner an average savings of 20 percent (Plant-Care.com, 2009). It can also improve the efficiency of an air conditioning unit by 10 percent (USDE, 2009).
Homeowners are strongly encouraged when improving their home to do many things to improve the home's resale value. One of the central keys in increasing the value is landscaping, in particular planting trees. By investing 5 percent of the home's value into landscaping, a homeowner can expect an increase in value of an average of 15 percent as well as increasing the speed in which homeowners sale their home by 6 weeks (Plant-Care.com, 2009). In one study in Ohio, it was predicted that in 2005 that 8.4 percent of all trees and shrubs to be planted were ash (Sydnor, 2007).
Emerald ash borer will change the energy consumption and the housing market in the United States and then there is the cost of dealing with the dead ash in the urban landscape. Using Lincoln, Nebraska as an example of the effect emerald ash borer can have on an urban environment. Estimated population of Lincoln as of 2008 is 251,264. The city owns 31,972 ash trees and there is 127,889 ash trees that are privately owned. The cost of removing and replacing 100 percent of all ash trees in the city will come to an estimated $137,403,770 (State of Nebraska, 2009). The estimated cost of removing, replacing and economic loss of the existing ash tree is $600-$800 (GPI, 2009). In one study, it was estimated that there are approximately 38 million ash trees growing on developed land. Over a 10 year period, it would cost $10.7 billion to remove and replace 17 million of the dead ash trees (Kovacs, 2009). The United States Forest Service conclude that due to the emerald ash borer decimating the ash trees in the urban environment, it will create a loss of approximately $20 to $60 billion dollars (USDA-APHIS, 2009).
The emerald ash borer has the potential to change the amount of energy consumed by the United States by simply removing all of the ash trees in the United States. The borer will increase the amount of energy that is necessary to run households that once were shaded by ash trees. One of the results of transporting, removing and replacing the fallen ash is that the United States' dependence on fossil fuels and oil will increase in order to deal with the effects of the emerald ash borer.
Efforts to Stop Emerald Ash Borer
The primary focus on stopping emerald ash borer has focused on 3 main points: research, quarantines and public awareness. The United States has approached emerald ash borer with a multi-agency effort in order to prevent the extinction of all native ash species. The United States Department of Agriculture, Animal and Plant Health Inspection Service, the Natural Resource Conservation Service, United States Forest Service, the Department of Interior, the National Parks Service, the Bureau of Land Management, many state and local agencies and many university systems are all key components in the research of the emerald ash borer. Research has been conducted in the area of emerald ash borer genetics, parasitic control agents, biology and chemical control, just to mention a few. There has been experimenting in ash tree genetics in finding if there is a way to natural prevent an infestation (MSU, 2009).
The quarantined area now includes locations in 13 different states as mention above (MSU, 2009). The effort in quarantining an area is for federal and state authorities to prevent the movement of infested wood from leaving the area. This is the main reason in the quick spread of the emerald ash borer. In helping in preventing the movement of wood, all the above mentioned agencies and states across the country have bombarded the media with information as a way to make the public aware of the situation. Signs, news articles, internet publications and even television coverage have all played a vital role in bringing the threat of emerald ash borer into the nation's mindset (MSU, 2009).
Many states have already prepared an emerald ash borer readiness plan if/when an infestation occurs. These plans outline what the potential effect of an infestation has on the state and outlines how state agencies will cooperate in order to deal with the invasion. Some states have conducted vast inventories of their ash resource in order to have a better understanding of the overall effect emerald ash borer could have on their state. Many of such programs have been grant funded through agencies such as the United States Forest Service. State agencies throughout the potential infestation area are working toward replanting and restructuring communities in order to not be completed devastated by an invasion. Programs like ReTree Nebraska focus on planting millions of trees in communities to not only combat pests such as emerald ash borer, but improve the state's local communities and tree diversity to avoid future pest problems (NFS, 2009).
Ash trees were heavily planted after Dutch elm disease eradicated most of the native elm trees that once lined America's streets and forest land. Now, much like then, a new pest has emerged to remove ash from our forest and our homes. The emerald ash borer is a small, but deadly pest. Emerald ash borer will drastically change the ecological and economical landscape of the United States in both our natural and urban environment.The $25.1 billion dollar ash timber industry is threatened due to this new pest problem (USDA-APHIS, 2009). 8 billion ash trees lost to one pest barely 1/2 inch long. Then there is the threat of wildfires, invasive species encroachment and heightened energy consumption because of the complete eradication of native ash trees. It is estimated that $20 to $60 billion will be lost in the urban environment. Estimates indicate that there is 38 million ash trees found in urban areas. If emerald ash borer were to continue its reign of destruction, it is speculated to cost $10.7 billion to remove and replace 17 million of the fallen ash trees (Kovacs, 2009). That is not even half of the resource estimated to be found in urban communities. Should the spread of emerald ash borer continue, the richness and diversity of the eastern United States will forever be changed.
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