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Emerald Ash Borer and
Milwaukee's Initiative
By Dylan Robert Weigel
Contents
Introduction .................................................................................................................................3
Life Cycle ....................................................................................................................................3
A Brief History of EAB .................................................................................................................4
Milwaukee's Plan ........................................................................................................................5
The Urban Forestry Internship ....................................................................................................7
Duties ......................................................................................................................................8
Consequences of letting the Invasive Flourish ..........................................................................11
Quantitative Losses ...............................................................................................................12
Qualitative Losses .................................................................................................................14
The System Set in Motion .........................................................................................................15
Our Current Status ....................................................................................................................16
Introduction
Emerald Ash Borer is an invasive beetle from Asia that kills Ash trees in its larval
phase. The Beetle was found in America in 2002 in Detroit, and has since then, been
sweeping across the United States. Anticipating this, Milwaukee founded a program
that uses college students to inject trees in order to stop the spread of this beetle.
Given the chance, this beetle could be detrimental to Milwaukee's commerce and
image.
Life Cycle
Emerald Ash Borer takes one or two years to complete its life-cycle depending
on; the timing of egg deposition, the health
and stress level of the tree, and local
temperatures(Gould et al. 2013). After they
emerge, Adult borers fly into the canopy and
feed on leaves for most of their lives(Gould et
al. 2013). After one week, they begin mating
and the females lay eggs 2-3 weeks after on
the trunks of trees(Gould et al. 2013). About two weeks after this, the larvae bore
through the bark to the phloem and out of the sapwood where they feed until the
weather cools down in the fall(Gould et al. 2013). As Winter approaches, the mature
larvae excavate pupal chambers in the sapwood and fold into an overwintering J-shape.
After development in the winter, they chew through the bark as adults and can fly out
immediately after. The damage to the tree comes in the larvae stage as the tunnels
they bore disrupt nutrient uptake, killing the tree from the top down.
A Brief History of EAB
Emerald Ash Borer, Agrilus planipennis, is an invasive species that was
discovered in the United States in 2002, in Detroit, Michigan, and Windsor, Ontario, also
in the summer of 2002. Since this initial infestation, clusters have been found every
year since then in; Ohio, Indiana, Illinois, Maryland, Pennsylvania, West Virginia,
Wisconsin, Missouri, Virginia, Minnesota, New
York, Kentucky, Iowa, Tennessee, Connecticut,
Kansas, Massachusetts, New Hampshire, North
Carolina, Georgia, and Colorado(Krause 2009).
There is no conclusive evidence to support their
method of arrival, but the most popular theories
are that they were transported in wood packing
material within a cargo ship, or airplanes coming from Asia, from which it
originates(Krause 2009). To date, EAB has cost these states hundreds of millions of
dollars, forced the implementation of stricter tree removal regulations, and cost
industries that utilize these trees tens of millions of dollars(Krause 2009). In order to
combat this invasive species, various methods of removal have been initiated in all of
these states such as removal of infected trees and introducing natural predators,
Wisconsin however, tried something different. In 2007 and 2008, Milwaukee's Forestry
Department studied different types of trunk injection in order find out which combination
of chemical and delivery system worked the best(Krause 2009).
Milwaukee's Plan
The City's preemptive approach on containing and eliminating the beetle came
as a reward to keeping a watchful eye on the destruction being wrought on the Midwest.
Seeing the trends unfold, the city began to create a management plan that was
threefold; Risk Assessment, Educating the public, and Risk Management.
The biggest challenge of risk assessment was to put into numbers, how
widespread , and to what extent of a problem scaled to. One method that was used
was a computerized spatial street tree inventory, or i-Tree Eco, and a hyper spectral
imaging-derived ash classification(Krause 2009). I-Tree Eco is a software application
designed to use field data from complete inventories or randomly located plots
throughout a community along with local hourly air pollution and meteorological data to
quantify urban forest structure, environmental effects, and value to communities.
Baseline data can be used for making effective resource management decisions,
develop policy and set priorities(Krause 2009). After these steps, it was apparent that
Milwaukee would be taking a huge risk to not acknowledge this threat.
The next step included educating elected officials in order to raise awareness
and gather support. Up until this point, Emerald Ash Borer was not thought of as a
threat to our City and State, bolstered by the fact that we had the dense concrete jungle
of Chicago to block its spread. These myths were obviously debunked after further
investigation, and the possible scope of this problem and its costs were made apparent
to city officials. The next obvious question revolved around the risk to the public, would
the treatment of these trees be detrimental to Milwaukee's citizens? After studying
different types of delivery systems, one method seemed to work the best, but was not
cost effective in terms of volume of pesticide, so for the time being, the program was
dead.
It wasn't until late 2008 that a new chemical, emamectin benzoate, or its more
common name; TREE-äge, was developed and showed promise for the project. What
was unique about TREE-äge was that it was able to provide protection for 2-3 years,
whereas other products required an annually application(Krause 2009). TREE-äge's
mode of action is a Chloride Channel Activator that prevents the insect muscle from
contracting(Krause 2009). This paralyzes the insect which stops it from feeding within
hours of ingestion, which compared to the 3-4 years it takes to kill the tree, this is the
blink of an eye(Krause 2009). At this point in time, there was only one company that
sold the restricted-use pesticide, Arborjet, so provisions were made and a budget got
put in place to buy all necessary equipment and chemical. By May of 2009,
preparations were complete and the project was able to commence.
The Urban Forestry Internship
Beginning in May of 2009, a total of 30 city employees were trained in order to
offer a large enough pool of trained injectors. The two main requirements of this
internship was the possession of a valid Wisconsin Driver's license, and a Pesticide
Applicator License (class 3.00-Turf and Landscape). The three lesser requirements;
basic tree identification, familiarity with a GIS map, and a basis in customer service
were used to separate applicants, which were mainly college students. The reason for
this was that it was a special project in that was only a seasonal position, and college
students for the most part, have younger backs. Once an ideal amount of applicants
was reached and then briefed, groups were formed and then given quarter sections of
the city to inject.
Groups were usually three or four in order to allow the rotation of duties because
some were more physically intensive than others. After arriving to the destination,
hydraulic guns were filled and calibrated with chemical, being careful not to waste what
was worth its weight in gold. This step of calibration was exceedingly important for a
few reasons. If the guns start injecting more pesticide than the tree can take up, the
pressure will force the bark to separate from the cambium, which will inevitably rupture
the bark, opening the tree up to infections. This may also cause the chemical to seep
out of the tree, wasting money and putting children and pets at risk due to accidental
ingestion. Though if the chemical going into the tree is lower than the desired amount,
then the treatment would be ineffective and could put the whole block or quarter section
at risk of being infected. Though this was kept in check by doing periodical calibrations
throughout the day and a chemical log of the expected versus actual volume of
chemical used.
Duties
The actual internship can be divided into five duties; DBH (Diameter Breast
Height) measuring, drilling, plug fitting, injecting, and sign posting.
Measuring the DBH is a crucial step
in this process because it determines the
amount of chemical being put into the tree
by determining the quantity of holes
needed. A measuring tape is wrapped
around the tree at breast height and then
its DBH is referenced against a dosage
chart for the number of holes to be drilled.
Once the trees have been
marked with the appropriate number of
holes, the person designated to drill,
drills 3/8 of an inch holes around the
base of the tree. It is important
however, that these e holes be spaced
out as uniformly as possible in order to allow an even concentration of pesticide to each
side of the tree.
The plug setting is one of the safety
mechanisms in these applications. The
person setting the plugs puts one plug into
each hole and then sets them by pounding
them in with a hammer. An efficient plug set
will be deep enough to stop seepage from
pressure within the tree, but not so deep that
the tree will not be able to exude the plastic plug. The plug is tapered at one end and
has a "user friendly" hole at the other allowing it to be set tight and aid the person
injecting.
Injecting is often the least
desired job as it is the most strenuous
and most dangerous. This job requires
the user to where a "backpack" for the
lack of a better word, which at
maximum capacity holds 1000psi in an
aluminum tank and about two liters of
chemical. The job itself is fairly easy in
that one just has to keep an eye on the pressure gauge and avoid seepage. One
hazard of this job however, is when the plug is not set deep enough, and the internal
pressure shoots pesticide back at the user. This is when knowledge of a restricted-use
pesticide comes in handy because there are specific ingestion, inhalation, and skin
absorption rates that apply for different chemicals.
The last duty, usually done by the person doing the measuring, is the posting of
pesticide application signs. Signs function to inform the community of the application,
and to alert other city employees of which quarter sections have been done. In regards
to the public, the signs show a word of warning in order to keep children and pets off of
the tree in case of seepage. They also inform the public of existence of Emerald Ash
Borer, and who they can call in order to learn more information about it.
Besides the primary objectives listed above, there is also a passive appearance
we strive for when representing the city. In one part, we need to represent the city as a
wise use of tax dollars and not give off the typical impression of a lazy city worker.
Keeping this image up reinforces faith in the government the services that it provides to
its taxpayers. We also need to play the role of informant, and alert citizens to what we
are doing, and why we are doing it. A typical conversation with a citizen would go as
such:
Citizen: Hey, what are you doing? Are you cutting down my tree?
Intern: Oh hello there, no we're not cutting your tree down, we are injecting them
for Emerald Ash Borer.
Citizen: What is that, one of those bugs?
Intern: Yes, it invades ash trees like the one you have in front of your house here.
Citizen: So my tree's infected?
Intern: No not at all, this pesticide is sort of like a vaccine that protects the tree if
the insect tries to infect it.
Citizen: Oh good, so how do I know if my tree is infected?
Intern: The tree will begin to look dead near the top and will have holes that have
the about the same diameter as a dime.
Citizen: If I think my tree is infected, who should I call?
Intern: There's a number on the pesticide signs that we're putting up, otherwise I
can give it to you now.
Citizen: Alright, thank you, try and stay out of the sun!
Though many of the conversations can go a lot more hostile than that with people
wanting us to chop down their tree or complaining about how the city hasn't fixed the
pothole in front of their house. In any case, most residents, whether it be in a lower-
class or upper-class quarter section, don't know about Emerald Ash Borer and its
effects on the ecosystem and neighborhood.
Consequences of letting the Invasive Flourish
With any invasive species, there will always be negative effects on the
environment due to the fact that it can either outcompete local organisms, or reproduce
faster than local populations. This can be detrimental to the system by either using up a
viable resource, or influencing the population trend towards a monoculture. In either
instance, if left unchecked, can have costly negative effects on the ecosystem.
Quantitative Losses
Ash trees make up around 20% of the total tree population in Milwaukee, not
including trees located in parks(EAB Statistic). Not treating for this insect would
inevitably lead to the loss of all of those trees, an average of one in five trees missing
per block. That is not a correct assumption though because there are many instances
where the whole block, both sides are Ash trees, which would mean a 100% reduction
in all of the things the urban canopy provides.
The loss of shade has a couple different effects on the surrounding communities.
Shade obviously provides a refuge to individual people and animals in the later days of
summer, but provides much greater services to the community as a whole such as
lowering the ambient temperature. Research done by Cambridge University found that
the urban forest "moderates the urban heat island effect, generally reducing the ambient
temperature as much as 6-8 degrees F during the summer, which in turn reduces the
amount of energy need to run air conditioners"(EAB Statistic). When extrapolated to
Milwaukee, there is a savings on summer cooling of $138,000 annually(EAB Statistic).
A loss of shade is always the most obvious problem because it is the one that
people immediately notice, but losing a canopy that big has more far reaching problems.
Not many people realize how much air pollution mitigation trees actually do for us. The
DNR has done extensive research and found that city trees actually perform a lot of
services for us such as trapping particle pollutants such as pollen and dust that can
damage our lungs, especially asthmatics(Trees Reduce Air Pollution). They produce
enough oxygen on each acre for 18 people every day(Trees Reduce Air Pollution).
They absorb enough CO2 on each acre, over a year's time, to equal the amount of CO2
produced by a car travelling for 26,000 miles(Trees Reduce Air Pollution). This
happens when the trees absorb pollutants through the pores in the leaves, and then
trapped and filtered(Trees Reduce Air Pollution). They are then washed to the ground
where they are absorbed by the soil and broken down by microorganisms such as
bacteria. If this canopy was lost, the city would lose $240,000 in air pollution mitigation,
meaning that if the city wanted to keep the current level of air pollution after losing 20%
of the canopy, it would have to invest $240,000 in order to do so(EAB Statistic).
Another service that this urban canopy provides for the city is the reduction of
stormwater into our sewers. Stormwater management has always been a high priority
in Milwaukee, evidenced by the $1 billion investment in the Deep Tunnel project. Also,
with restrictions from the State and MMSD in regards to stormwater regulation,
provisions would have to be made in order to deal with essentially adding all the water
that was usually regulated by the street trees, into the already overloaded system. To
quantify this, a 20% reduction in our urban canopy would be a loss of $2.6 million in
storm water regulation benefits(EAB Statistic).
Qualitative Losses
While these services are important, they only take into consideration the
quantifiable, and not the qualifiable losses such as habitat loss. Not so much habitat
loss per tree, but habitat loss due to defragmentation of the whole metapopulation.
Ecosystems that sprawl the area of an urban
canvas are often patchy as large areas are
seldom found. This means that the
interconnectivity is especially important and
removing one tree or "corridor" may displace not
only the species utilizing that tree, but all those
who use it for transportation and periodical feeding. The effects are almost impossible
to accurately quantify because we can't know every species living within one of these
trees and how exactly they benefit from it.
Another qualitative loss could be in the City's
aesthetic image, because beauty is in the eye of
the beholder, but then again, not many people are
moving to Detroit nowadays. Stemming from
personal experience, it is just awe-inspiring to drive
down a street and have the entire street shaded with small inlets of sun, engineered by
an archway of branches. It is especially challenging when we are trying to change the
city's image from a "conservative, frugal factory town to vibrant, livable and
cosmopolitan city", when we are in the middle of the "Go Green" era and we are losing
20% of our poster child(Chicago Tribune). Though these losses seem tame when
compared individually, they can be a collaborative loop of amplifying variables when set
in motion.
The System Set in Motion
To say that that these consequences happen in somewhat a linear fashion is a
misnomer, because the same driver can come back and influence the system later on in
the cycle. The immediate loss to the city is in tax dollars, about $750 to remove and
replace each ash tree(EAB Statistic). Seeing as there are 36,000 ash trees on the City
streets, the total escalates to $27 million(EAB Statistic). Milwaukee's Forestry District
Budget for 2014 is $6,899,910, conservatively, if it takes 10 years to remove all of the
trees, that's still an extra $2.7million per year(City of Milwaukee Budgets). The problem
is, that there is no negotiation here, infected trees must be taken down due to safety
hazards, which means that either taxes will have to get raised, or the money will have to
be taken from elsewhere. Taxes are already on the rise and will continue to do so, the
most likely cut would be from within the Forestry Department under Nursery Operations.
What this would mean, would be a decline in aesthetics, such as degradation of flower
beds, and because of the increased work load for the Arborists, less tress being pruned.
Once this removal is over and all the new trees are planted, it's still not over. A
decline in aesthetics leads to a decline in property values, evidenced by such
neighborhoods as 76th and Good Hope Rd. Lower property values bring in less
desirable inhabitants, and in turn bring in less desirable, cheaper businesses, and with
this turnover in middle to lower class inhabitants, comes more abuse to the canopy.
Going through neighborhoods in almost every section of our City, and finding trees;
Ash, Oak, Maple, etc. spray painted with gang signs or birthday messages, or bark
completely stripped off for reasons unknown to myself, exposing these trees to a new
invasive, repeating the entire cycle over theoretically, leading to more decline, and more
tax dollars.
Our Current Status
Currently, the program is budgeted to have about $1 million each year, allowing
the City to treat for 20 years before even getting close to the $27 million mark(EAB
Statistic). During this time, the oldest and most infected Ash are removed and a new
species is planted in its place. Staggering the growth of these trees allows
neighborhoods to not completely lose their urban canopy and any of its benefits. As the
program moves along, more and more constituents are made increasingly aware of the
problem on the horizon, and may help us get a handle on this before Milwaukee falls
into the same fate as cities such as Detroit.
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