Pittsburgh Park Trees Action Plan
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Transcript of Pittsburgh Park Trees Action Plan
2012 Action Plan for Park Trees
Addressing Immediate Threats to Trees in Pittsburgh’s Parks
Oak wilt and Emerald Ash Borer
April 2012
The City of Pittsburgh Pittsburgh Parks Conservancy
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TABLE OF CONTENTS
Executive Summary ....................................................................................................................................................... 5
Scope and GOAL of the Plan .......................................................................................................................................... 6
ACTION TAKEN (2011) ................................................................................................................................................... 7
NEXT STEPS (2012) ......................................................................................................................................................... 7
Communications Plan .................................................................................................................................................... 8
Key Messages ............................................................................................................................................................ 8
Education and Training............................................................................................................................................ 10
Threats Defined ........................................................................................................................................................... 12
Historic Threats to Tree Health ............................................................................................................................... 12
EmErald Ash Borer................................................................................................................................................... 12
Oak Wilt Disease ..................................................................................................................................................... 12
White-Tailed Deer ................................................................................................................................................... 13
Inventory: Park Landscape Trees ................................................................................................................................. 14
Inventory: Natural Areas Study ................................................................................................................................... 14
Creating Conservation Sites ......................................................................................................................................... 15
Genetic testing ........................................................................................................................................................ 15
Tree removal ................................................................................................................................................................ 16
Higher-End Use of Removed Trees.......................................................................................................................... 16
Recent Native Tree Preservation Approaches ............................................................................................................. 18
American chestnut .................................................................................................................................................. 18
American Elm .......................................................................................................................................................... 18
Current Native Tree Preservation Approaches ............................................................................................................ 19
Green and White ash............................................................................................................................................... 19
Hemlock .................................................................................................................................................................. 21
Red oak group ......................................................................................................................................................... 22
Oak Wilt Management in Pittsburgh Parks ............................................................................................................. 22
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Invasive species ........................................................................................................................................................... 23
Invasive Species Control .......................................................................................................................................... 23
Adaptive management ................................................................................................................................................ 24
Pending Threats ........................................................................................................................................................... 24
Asian Long-horned Beetle ....................................................................................................................................... 24
Beech Bark Disease ................................................................................................................................................. 25
SIrex WOODWasp ................................................................................................................................................... 25
ASIAN Ambrosia Beetle ........................................................................................................................................... 26
Gypsy Moth ............................................................................................................................................................. 26
Thousand cankers disease ....................................................................................................................................... 26
Appendix A: TREE EXPERTS CONSULTED ................................................................................................................. 29
Appendix B: Native Trees and Related Threats ....................................................................................................... 30
Appendix C: Tree Species and Frequency by Park, from Natural Areas Study 2010 ............................................... 31
Appendix C (Continued): Tree Species by Density, from Natural Areas Study 2010 ............................................... 32
Appendix D: Insecticides Effective in Controlling EAB............................................................................................. 33
Appendix E: Tree Species planted in the Pittsburgh City Park Woodlands ............................................................. 34
Appendix F: Photo credits ....................................................................................................................................... 35
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PART 1
Executive Summary, Plan Development,
Immediate Steps,
and Communications Plan
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EXECUTIVE SUMMARY
Trees are a signature feature of our parks. They create the woodland experience that all park
visitors love. And in addition to providing an experience of “nature,” trees provide many
environmental services. They stabilize hillsides, control storm water, clean our air and reduce
air temperature, while providing habitat for wildlife.
In the next decade, Pittsburgh is expected to lose a significant number of native trees due to
disease, introduced insects, and the effects of deer overpopulation. The situation reached a
critical point in 2011 because of the convergence of a devastating new pest—the Emerald Ash
Borer (EAB) beetle—with continued outbreaks of oak wilt disease and the expected arrival of
other destructive pests like the Asian long-horned beetle, sirex wood wasp, and Asian ambrosia
beetle. Beech Bark Disease has reached Allegheny County and Thousand Canker Diseases is
already in eastern PA.
There is no feasible way to save all of the park trees under threat1 from this overwhelming
combination. Yet there are ways to mitigate the effects of these pests and improve the health
of the city’s parks woodlands at the same time.
The purpose of this plan is to provide an immediate and tactical response to the current threats
of emerald ash borer and oak wilt disease, while keeping a watchful eye for new threats, and
new treatment strategies. The action plan delineates first steps and key messages, outlines
historic threats, and explains the current ones. The balance of this document speaks to
strategies for preserving tree species and managing current and emergent threats to urban tree
health in parks.
1 “Rare,” “threatened,” and “endangered” are official terms that the Pennsylvania Department of Conservation
and Natural Resources uses to define plant and animal status in the Commonwealth. “Plant species listed as Pennsylvania Endangered are in danger of extinction throughout most or all of their natural range within this Commonwealth. Plant species which may become endangered within the Commonwealth are listed as Pennsylvania Threatened. Plants found only in restricted geographic areas of the state or in low numbers are classified as Pennsylvania Rare” (PA DCNR, “Rare, Threatened, and Endangered Plants”). None of the species that are the subject of this document currently have a legal status, although that may change in the future.
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SCOPE AND GOAL OF THE PLAN
The goal of this plan is to minimize the loss of park trees and speed forest recovery now.
These threats are an issue across much of the nation, and are most likely the byproduct of
increases in global trade and travel. To get a larger perspective, the Pittsburgh Parks
Conservancy and the City invited experts from Michigan, West Virginia, New York, and several
members of PA’s Department of Conservation and Natural Resources (DCNR) to visit Pittsburgh
in November 2010 to examine the situation. That work session plus ongoing research and
communication with these and other experts culminated in this action plan.
The greatest numbers of “at-risk” public trees are found in city parks, in greenways, and on
hillsides. To a lesser degree, at-risk trees are found on city streets in the right-of-way. However,
an even greater number of trees exist on private property within Pittsburgh city limits. The
focus of this action plan is to develop strategies for managing threats to trees in City-owned
parks, but the same methodology may be applicable to other trees as well.
This is an immediate and tactical response to specific threats and will guide and coordinate the
efforts of the City, the Pittsburgh Parks Conservancy, Mt. Washington Community Development
Corporation (Emerald View Park), Allegheny Commons Initiative, and our volunteers as we
jointly address tree loss and replacement throughout the city’s parks.
This plan includes a forest restoration strategy and the practice of creating species conservation
sites in the four historic RAD-funded parks, while managing the decline of trees that cannot be
saved.
It is important to note that the plan incorporates an Adaptive Management approach, meaning
that we learn from our work and others, incorporating our learning into future management
decisions. Management strategies best suited for geographic and site conditions, public safety,
and the greatest environmental benefits are the core values within this plan.
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ACTION TAKEN (2011)
With emergency funding raised by the Pittsburgh Parks Conservancy, several steps have already
been taken by City and Parks Conservancy staff:
1. Ash Conservation
a. Identified, assessed, and mapped white and green ash in the City’s parks in early
2011. 158 specimen ash trees were selected for conservation.
b. Explored different treatment options for specimen trees to determine the best
method for each location. Considered trunk injections of insecticides, chemical
sprays, and soil drenches. Trunk injections of Emamectin benzoate were
determined to be most effective in preserving ash trees, while minimizing spread
of pesticide.
c. Hired a contractor that completed ash tree trunk injections before the end of
June. Studies of use of the insecticide elsewhere indicate that the trees will need
to be re-injected in 2013 and again in 2015.
d. Collected seed from specimen trees to be used for conservation.
2. Oak Wilt Disease - Identified outbreaks in Frick and Riverview Parks.
3. Began to execute a communication and education plan to recruit volunteers, increase
awareness, and generate donations.
a. Held Feb 17 public forum with tree experts to present the critical threats and
need for response.
b. PPC publicized threats to park trees through Parks Conservancy newsletter The
Voice and blog. Article published in Pittsburgh Post-Gazette.
c. Fundraising appeals sent to Parks Conservancy donors.
d. City 311 operators trained to handle reports outbreaks of oakwilt or hazardous
trees.
4. Funding sources: City applied for federal funding for oak wilt management and ash
conservation in cooperation with DCNR.
NEXT STEPS (2012)
1. Ash Conservation
a. Monitor trees previously treated with Emamectin benzoate to assess tree health.
Trees will die back prior to full recovery; prune dead/hazardous limbs as
appropriate. Fertilize and water treated specimen trees as needed.
b. Look for additional ash trees for conservation. Candidate trees more likely to be
found in south and east ends of the City, as EAB is well entrenched in the north
and central parts of the city.
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c. Continue research into pesticide use and applications.
2. Oak Wilt
a. Address existing outbreaks of Oak Wilt Disease identified in Frick and Riverview
Parks following established protocols.
b. Continue to watch for new outbreaks.
3. Continue collaboration between the City and the Pittsburgh Parks Conservancy to
execute a communication and education plan whose goal is to recruit volunteers,
increase awareness, and generate donations.
4. Identify funding sources:
a. Dedicate City contractors under the City Forester to address hazardous tree
removals and other related tree work.
b. Present plan to major foundations, corporations, and state and federal agencies.
5. Site Restoration
a. Remove park trees that are hazardous (City Forester). Find higher-end use
destinations for the wood of ash, oak or other invasive and non-native species
removed to offset removal costs.
b. Assess and create site-appropriate restoration plans, to include slope
stabilization, invasive plant control, replanting, deer protection, and
maintenance.
6. Update park landscape tree inventories databases.
COMMUNICATIONS PLAN
KEY MESSAGES
Development of this Action Plan for Park Trees was thorough and based on input from
many experts.
Pittsburgh’s park woodlands have experienced pests and disease in the past, such as
Dutch elm disease and chestnut blight. However, the City’s park trees have never faced
a convergence of such devastating threats at one time.
Emerald ash borer, oak wilt disease, and white-tailed deer are causing the greatest
damage now.
o More threats are on the way, such as Asian long-horned beetle. Evidence of
Beech Bark Disease has been found in Allegheny County. Thousand Canker
Diseases has been detected in eastern PA.
We can’t save all of the trees under threat; we can only save selected specimens and aid
in the recovery process.
Conserving tree species under threat is a commitment with no foreseeable end.
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Losses will occur in all parks; the damage is noticeable now.
Decline is rapid, recovery is slow.
o It will take generations to recover from tree losses expected in the next ten
years.
The four RAD-funded historic parks (Frick, Highland, Riverview, and Schenley) will serve
as the model for other parks and urban forest restoration.
There are approximately 373,000 trees on 900 acres of park land in the RAD parks.
o Almost half of these trees are non-native and invasive.
o Green and white ashes comprise over 14% of the woodland trees.
o Almost all of the RAD parks’ 53,000 ash trees will die by 2020.
o The red oak family most susceptible to oak wilt includes 45,000 trees.
The prediction for loss is less dire than for ash because of existing oak
wilt control protocols.
Funding is needed for treatment and recovery, including:
o Planning and design expenses
o Infected tree identification and mapping
o Tree removal and subsequent site restoration
o Treatment, including labor and materials
o Conservation site construction
o Planting and maintenance of newly planted trees for three years
o Seed collection
o Volunteer coordination
o Public education
Preservation of trees is crucial because of the many benefits they provide. Trees:
o Intercept rainfall, filter it, and reduce storm water runoff, keeping it out of the
sewer system and saving the expense of treatment
o Stabilize hillsides
o Reduce heat island effect in cities
Provide shade . . . . .
Absorb solar radiation
Promote evaporative cooling
o Reduce electricity costs by shading buildings and shelters located in parks,
leading to less pollution from electricity-generating plants
o Remove carbon and other particulate matter from the air
o Increase property values through aesthetic properties
o Provide habitat and promote biodiversity
o Define Pittsburgh’s image as a green city
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EDUCATION AND TRAINING
Pittsburgh Parks Conservancy
o Newsletters, e-mails, blogs, appeal letters
Volunteers
o Volunteer Days
o Urban Eco-Stewards Training
General Public
o Media advertising (funds pending)
o Signs at multiple access points to educate park users about pressures on the
urban forest and steps being taken to mitigate losses.
PART 2
Threats Defined, Tree Inventory &
Conservation Plan
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THREATS DEFINED
HISTORIC THREATS TO TREE HEALTH
Trees have a history of rebounding from such environmental impairments as timber harvesting,
land development, toxic soils and air, poor forest management, and invasive species, as well as
disease organisms. Dutch elm disease, for example, virtually eliminated the entire population
of American elms during the 1960s and early 1970s, and chestnut blight decimated the
American chestnut population during the 1930s.
See Appendix B for a list of threats by tree species.
EMERALD ASH BORER
An exotic beetle native to Asia, the emerald ash borer (Agrilus
planipennis) was discovered in Michigan in 2002. It is thought to
have arrived in North America in wood shipping crates from Asia.
The adult beetles nibble on ash leaves but cause little damage. The
larvae (the immature stage) feed on the inner bark of ash trees,
disrupting the tree's ability to transport water and nutrients.
In less than 10 years, EAB has killed tens of millions of trees in 12
states in the U.S. and two Canadian provinces. While insecticides
can reduce the population and spread, widespread use is not
viable. Individual high-value trees can be protected by injections,
but the cost is prohibitive for widespread use.
When EAB was first discovered in Detroit in 2002, City of Pittsburgh park crews and Parks
Conservancy staff stopped planting green ash (Fraxinus pennsylvanica) and white ash (Fraxinus
Americana) trees, anticipating that the insect would reach Pittsburgh. EAB was detected in the
Pittsburgh area in 2007.
OAK WILT DISEASE
Oak wilt is an aggressive disease, caused by the fungus Ceratocystis fagacearum that affects
many species of oak. It is one of the most serious tree diseases in the eastern United States,
killing thousands of oaks each year in forests, woodlots, and home landscapes. Oak wilt was
first identified in 1944. Some plant pathologists think that oak wilt is an exotic disease, arriving
in North America in the early 1900s, but the fungus has never been reported in any country
other than the United States. The disease has also become much more apparent in some local
EAB damage on a White Ash
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areas since the 1980s because of increased tree wounding, due primarily to home construction
in oak woods.
In 2010, a total of 10 acres in three of
Pittsburgh’s regional parks were cleared
because of oak wilt disease. A tree cannot
be saved once it is found to have this
aggressive vascular disease, but the
disease can be contained. The City of
Pittsburgh has a protocol (explained later
in this document) for dealing with oak wilt.
In 2011, outbreaks of oak wilt disease
were found in Frick Park and Riverview
Park.
WHITE-TAILED DEER
The city’s parks have an average of 51 – 60 deer per square mile (U.S. Department of
Agriculture 2010). This is much higher than the historic population levels of white-tailed deer
(Odocoileus virginianus). The populations are high because conditions are quite different in
Pittsburgh’s parks than they are in wilder places; there are no predators, and there is not as
much forest cover as there once had been.
Deer are herbivores that browse on most plants in the
urban forest with a few exceptions (black cherry, spicebush
and garlic mustard). As a result, deer have eaten many of
the small trees and shrubs in park woodlands and
prohibited healthy regrowth of our forests. For example,
in Riverview Park spicebush is the dominant understory
plant. In a healthy forest, there would be more kinds of
shrubs present and the small trees would be numerous.
In 2002 Dr. Ann Rhoads, Senior Botanist at the Morris
Arboretum and co-author of The Plants of Pennsylvania,
visited Pittsburgh’s RAD parks. She said that the larger forested areas in the parks “are more
severely impacted by deer overabundance” than by invasive species. There is conspicuous
absence of understory vegetation, including tree species. Any number of forest plant
communities will develop depending on seed source, competition for light, soil conditions, and
pressure from browsing animals like deer, rabbits, etc.
Containing Oak Wilt in Frick Park, 2010
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INVENTORY: PARK LANDSCAPE TREES
An inventory of park landscape trees (those planted by design) was completed over a two-year
period, concluding in 2007. The inventory provided locations, species, sizes, and general
condition of these trees; the inventory also included tree maintenance recommendations from
certified arborists who conducted the inventory. The inventory enabled the City and Parks
Conservancy to quantify the extent of impact by diseases and insects upon much of the urban
forest and to develop a maintenance plan for pruning and removal.
INVENTORY: NATURAL AREAS STUDY
While it is a good management tool for the landscaped
portions of the parks, the tree inventory did not include
the numerous trees in park woodlands. The City’s
Department of Planning, as recommended by the
Regional Parks Master Plan, completed the Natural Areas
Study (NAS) in 2010, filling the gaps in the 2007 tree
inventory.
The NAS revealed that there are approximately 373,000
trees on 900 acres of park land in Frick, Highland,
Riverview, and Schenley Parks. Unfortunately, almost half
of these trees are non-native, invasive species. The City
and Parks Conservancy have existing management control
plans to address these issues.
The park tree inventory and the NAS provide baseline information and outline challenges and
opportunities in our urban forest.
See Appendix C for tree inventory and Natural Areas Study detail.
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CREATING CONSERVATION SITES
Conservation sites will be established to protect areas in the four RAD-funded historic parks
where genetically diverse species that are under threat can be planted, protected, and
monitored. Some conservation sites will require deer fencing; others may simply be delineated
by signs. Trees threatened by disease and insects will be treated in these areas to preserve
specimens of their respective genera. Other species under threat will be planted here as well if
site-appropriate for preservation purposes. Conservation sites will vary significantly on a per-
site basis; however, all will be mapped and inventoried on a frequent basis.
This strategy is a good fit for urban forests, rather than wilderness areas. It requires a highly
skilled work force, a detailed plan, appropriate equipment, and worksite proximity to operation
centers. The City of Pittsburgh has access to ISA Certified Arborists and certified pesticide
applicators as well as bucket trucks and all of the other equipment necessary to conduct
preservation operations.
One aspect of managing the conservation area is to reduce overall stress on the site. The
proportion of non-native and invasive trees, shrubs, and herbaceous plants must be managed
on a site-specific basis in order to optimize growth conditions of preserved species.
GENETIC TESTING
The Parks Conservancy has a research relationship with the Carnegie Museum of Natural
History, Pittsburgh, and Dr. Cynthia Morton, Associate Curator and Head of Botany. The Parks
Conservancy and Dr. Morton have effectively collaborated to study the genetic diversity of
London plane tree cultivars, using the AFLP2 method.
Knowing the genetic diversity of trees in a conservation area is extremely important to the long-
term viability of the species.
2 amplified fragment length polymorphisms (AFLPs)
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TREE REMOVAL
In some cases, it may be necessary to remove non-native invasive and native species that are
dead or dying, structurally defective, or an alternate host for another destructive disease or
insect. This is especially true when dead or dying trees are located near park trails, roadways,
and cultural landscapes.
Tree disposal must be carried out in a fashion that will not allow for the movement of the insect
or pathogen from the removed tree tissue.
Removals and wood utilization opportunities may create return value for the removal
contractor. In some instances using portable saws to create lumber on site will be best. The
contractor could keep the excess from the job as barter for their services.
Another consideration would be to allow interested parties to bid on standing timber in areas
where tree losses are expected to be extensive.
HIGHER-END USE OF REMOVED TREES
Below are examples of public information websites created in response to extensive tree loss
and removal in other metropolitan areas.
Urban Wood Use Planning Worksheet for Communities: This worksheet helps an urban forest
manager to work through the opportunities and challenges of developing a wood utilization
plan. http://semircd.org/ash/news/UrbanWoodUsePLanningWorksheet.pdf
Cost Effective Tree Removal Strategies: Covers wood utilization strategies for communities and
urban areas. http://semircd.org/ash/news/Cost%20Effective%20Tree%20Removal.pdf
City of Olympia Wood Waste Recycling Program: Example of a comprehensive city-wide plan
for handling wood waste. http://www.ci.olympia.wa.us/NR/rdonlyres/8825122E-5317-4DBC-
9611-B3FA697160A4/0/WoodWasteRecyclingReport.pdf
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PART 3:
Tree Preservation by Species
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RECENT NATIVE TREE PRESERVATION APPROACHES
AMERICAN CHESTNUT
The American Chestnut Foundation (TACF) was formed in the mid-1990s to breed surviving
American chestnut trees (Castanea dentata) with blight-resistant Chinese (Castanea mollissima)
and Japanese (Castanea crenata) chestnut trees. This would add blight resistance to American
trees and eventually breed out all of the non-native physiology. This work was originally
undertaken by the Department of Agriculture when the disease was destroying the chestnut
trees, but discontinued when the population of chestnut was lost—hence the formation of
TACF.
Breeding work of this type takes 30 to 50 years to achieve a hybrid chestnut tree that looks and
grows like an American chestnut, yet has full blight resistance.
The City entered into an agreement with TACF in 2001 to plant early hybrid chestnut trees to
observe growth performance and blight resistance in the Pittsburgh area. This planting is
located in Highland Park next to Forestry headquarters.
Allegheny County parks have similarly engaged with TACF to observe growth performance and
blight resistance in South and North Parks. Volunteers from TACF maintain the plantings, record
data, and harvest seed to be used in future breeding efforts.
AMERICAN ELM
During the late 1960s through the 1970s, American elm trees (Ulmus americana) lined
Pittsburgh’s streets and landscapes. Many of these trees were removed because of the Dutch
elm disease (DED). DED is a non-native disease that was imported to the United States on a
shipment of logs from Europe. Some American elms still remain, having weathered the initial
insurgence of the disease. This residual population of mature trees continues to decline. As
they do so, many seedlings emerge and become quite sizeable.
Tree breeders have used the surviving American elms to cross with other species of elm and
create disease-resistant cultivars. Some of these cultivars look like American elm, but most do
not. Some of these cultivars will become excellent street and landscape trees, but it is still
undetermined if any would be suitable as forest or timber-type trees.
Schenley Park has a comprehensive collection of elm cultivars planted for observational study.
Characteristics being evaluated are: disease resistance, growth rate, fall color, habit, form, seed
production, invasive potential and winter interest (exfoliating bark).
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CURRENT NATIVE TREE PRESERVATION APPROACHES
GREEN AND WHITE ASH
TACF provides a model which can be emulated to attempt the restoration of native ash trees to
their original range. Having Pittsburgh participate in this endeavor means that Southwestern
Pennsylvania will someday have ash trees restored to the environment. Even though the ashes
have many native insects and diseases that attack them periodically, they remain a valuable
forest and landscape species. There are three parasitoids that have been released and are
under study for their effectiveness as biological controls for EAB.
See http://www.emeraldashborer.info/files/EAB-FieldRelease-Guidelines2010.pdf.
In the parks landscape tree inventory, white ash represents 112, and green ash 59 trees, for a
total of 171 ash trees in the developed (non-forest) landscape. Thousands more make up our
woodlands as shown in this table from the Natural Areas Study.
Park Landscape Woodland Total
Frick 2,600
Highland 2,316
Riverview 2,976
Schenley 45,531
Total 171 53,423 53,594
JANUARY TO MARCH
Select genetically superior trees in urban woodlands and park landscapes; map locations
using GPS.
Select historic/culturally important ash trees; GPS locations; avoid selecting landscape
ash trees that are cultivars.
Must select male and female trees in close proximity to one another.
Update the ash inventory in the parks with EAB infestation component included.
APRIL TO JUNE
Inspect selected ash tree specimens for flowering attributes. Accept or reject specimens
for treatment based on sex. (This species is dioecious.)
Determine treatment priorities for the City (e.g. historic, hazardous, right-of-way,
ecologically significant trees, etc.).
Choose the management approaches for each treatment priority (cultural, mechanical,
chemical, biological, etc.).
Implement treatment according to the plan.
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Treat selected ash tree specimens with Emamectin benzoate insecticide by trunk
injection.
Note: Insecticides that can effectively control EAB fall into four categories:
1. Systemic insecticides that are applied as soil injections or drenches;
2. Systemic insecticides applied as trunk injections;
3. Systemic insecticides applied as lower trunk sprays; and
4. Protective cover sprays that are applied to the trunk, main branches, and—
depending on the label—foliage. (See Appendix D: Insecticides Effective in
Controlling EAB for a list of effective insecticides.)
JUNE TO OCTOBER
Water trees during droughts.
Selective use of tree growth regulators on high value forest and landscape trees aids
effectiveness of insecticide injections.
AUGUST TO NOVEMBER
Periodically: prune as required, apply fertilizer.
YEAR-ROUND
Remove infested trees as resources become available, but PA DCNR recommends
removals during months of Nov.–Mar. while larvae or prepupae are overwintering
under bark.
LONG TERM
Perform genetic testing of selected specimens in order to assure maximum diversity.
This is important with restoration efforts of the species. It will prevent the “bottle neck”
effect in plant breeding.
Document all activities and collect data.
Report progress and results bi-annually or annually.
MITIGATION EXPENSE EXAMPLES
Removal of 1 tree for safety purposes:
o $650 per average tree
Preservation of 1 specimen tree:
o Average diameter 24”@$4.50 per inch = $108 per year
Genetic testing for 1 specimen tree:
o $5,000 (one-time expense)
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Cost to plant street trees
o $700-$800 for planting only
o Up to $2,000 for tree removal and replacement
Staff time to manage program:
o $35,000 per year
HEMLOCK
The Eastern hemlock (Tsuga canadensis) is the
Pennsylvania state tree. It is currently under
threat from elongate hemlock scale (EHS)
(Fiorinia externa Ferris) and hemlock woolly
adelgid (HWA) (Adelges tsugae). Both insects
can be treated with soil drench systemic
insecticides. Even though Eastern hemlock has
very low numbers in Pittsburgh’s regional parks,
several isolated trees and small stands exist and
should be preserved. Hemlock populations were
probably higher historically in many areas and
could be augmented in selected areas with the understanding that they will require treatment
every five years or so.
Phipps Run in Schenley Park is an isolated area that provides an excellent location for
preserving hemlock. An initial planting was done with volunteers in 2005. Inventory the
original planting and augment as necessary.
In Highland Park, along the Mayor’s trail, there is a small population of mature hemlock
trees that should be in conservation areas. Plant more hemlock seedlings in this area.
March through May 2011: monitor for elongated scale and woolly adelgid. (The woolly
masses become degraded and difficult to identify as the summer progresses.)
The Mairdale stream in Riverview Park also has a small population of hemlock trees.
Plant more hemlocks in this area. Monitor for elongated scale and woolly adelgid.
Treat with soil drench insecticide as required for insect infestation; frequency can vary
from one to seven years. Imidacloprid will provide up to five years of protection from
HWA but has no effect on EHS. Dinotefuran is required for control of EHS. This could be
possibly applied at the same time as Imidacloprid depending upon return infestation
levels of EHS.
Document all activities.
Collect data.
Report progress and results bi-annually or annually to partners and key audiences.
Hemlock Woolly Adelgid
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RED OAK GROUP
The most common oaks in the red oak group of trees are red (Quercus rubra), black (Quercus
velutina), and pin (Quercus palustris). The Pittsburgh region has seen oak wilt disease devastate
public and private landscapes. By the time the disease is noted in a member of the red oak
group, the fungus has already spread to the root system. It is a disease that, once introduced to
an area, will continue to spread from susceptible oaks via root grafts and several types of sap
feeding beetles.
Total number of red, black, and pin oak trees by park:
Park Landscape Woodland Total
Frick 5,200
Highland 9,264
Riverview 11,904
Schenley 17,786
Total 1,092 44,154 45,246
OAK WILT MANAGEMENT IN PITTSBURGH PARKS
The following protocol was established in 2010 for oak wilt outbreaks in the RAD-funded parks
and updated in 2012 per USFS and PA-DCNR guidelines:
Root trench prior to tree removal to prevent translocation of disease through root grafts
between diseased and healthy trees. Experts recommend using a wheel trencher as
opposed to a chain trencher.
Contractors are told to avoid excess disturbance of trails, and they are responsible for
backfilling and tamping trench area.
Remove ALL red and white oaks from project area. This includes removal of all bark and
wood debris from site, including existing debris. All infected tissue except that which has
a higher second use as noted below should be chipped on site prior to removal from
site.
Contractors will make a good faith effort to find highest second uses for tree parts,
including lumber and art work, prior to designating wood for biofuel or mulching uses.
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No end source of wood parts shall allow tree trunks to go unprocessed later than
December of the project year in order to ensure that no spore mats from the disease
are allowed to develop in another location. Process for verification should be in place.
Tree parts sent for mulch or biofuel shall be chipped/shredded prior to leaving the site.
Plans to transfer wood for higher use shall be reported to the City Forester to track
movements of wood from diseased areas, to verify chipping of all residual wood tissue
prior to December of the year of removal, and to learn about any creative uses found
for the wood.
All oak stumps are to be sprayed with Roundup immediately after the tree being felled.
If the contractor cannot comply with an immediate application of Roundup, the stumps
may be sprayer later but only after a fresh layer cut has been made to the stump. All
stumps must be treated within the same working day of the tree removal.
Contractor awarded work will include an educational component at the direction of the
City Forester, whether it be to school students or adults, in order to foster
understanding of the disease cycle and the need for tree removals.
INVASIVE SPECIES
The City and Parks Conservancy have long-standing protocols for controlling woody and
herbaceous plant species within the parks. We recognize that these non-native and invasive
species introduced by horticulture have escaped our landscapes and populated urban and
remote woodlands. Outside of their native habitat, these species are able to increase rapidly
without any natural controls such as herbivores or diseases. These plants then threaten the
native species of their adopted home, as they can out-compete them for light, space and
nutrients.
INVASIVE SPECIES CONTROL
Conservation of the listed tree species and their sites is not possible with a large population of
multiple invasive species in the same area. Mechanical and chemical removal and maintenance
of select invasive species should be completed.
Control and maintenance of areas with invasive and non-native species bordering conservation
sites and the parks is necessary to reduce ingress into conserved areas. If there are invasive
park landscape trees, remove them and plant replacement trees. This will then remove
unwanted seed sources.
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ADAPTIVE MANAGEMENT
Assessment needs to happen on a site-by-site basis,
learning from methods that were used in previous
projects and adjusting management protocols. For
example, there were two different methods used in Frick
and Highland Parks to address oak wilt disease. When
oak wilt disease was contained in Frick Park (2010), the
site was clear-cut. This decision was made because the
site was relatively level, with less chance for erosion, and
surrounded by moderately healthy forest, with a better
chance for healthy forest regeneration. That said, clear-
cutting an entire large section of forest should be
considered very carefully; it shouldn’t happen unless
there are no other options. In Highland Park, the site is
on a steep slope, on the edge of a two-acre vine-infested
canopy gap and a right of way infested with Japanese
knotweed. Clear-cutting the site would have been a bad
decision; there would have been bare soil prone to erosion and
no shade to discourage infestation of invasive species. Highland
Park removal efforts were targeted only to affected oak species and left the Norway maple
understory. Also, the restoration strategy post-removal changed to suit the site.
PENDING THREATS
ASIAN LONG-HORNED BEETLE
Native to parts of Asia, the Asian long-horned beetle
(Anoplophora glabripennis) is believed to have arrived
in cargo shipments from Asia. The Asian long-horned
beetle (ALB) prefers to feed on maple trees, but
infestations have also been discovered in horse
chestnuts, poplars, willows, elms, mulberries, and
black locusts. Mature beetles are very large with
bodies ranging from 1 to 1½ inches in length and
antennae which can be as long as 4 inches. Currently,
there is no known chemical, biological, or natural defense against this beetle in North America.
However, the insecticide Imidacloprid is currently being tested in New York and other eastern
Oak Wilt Site in
Highland Park
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seaboard communities as a trunk injection control mechanism for ALB. If this product and
technique are demonstrated as effective, it will be incorporated into this plan. Community
education regarding the movement of firewood and other natural products from different
locales is critical in slowing down this and other alien insects.
BEECH BARK DISEASE
Beech bark disease (BBD), a complex affecting American beech (Fagus grandifolia), includes both insect and fungal components. The classic concept of BBD, first articulated by Alex Shigo in 1972, remains the standard for today's forest pathologists. Alex described three arbitrary, temporal disease phases: the initial scale front phase, the second killing front phase, and the final aftermath forest phase. During the initial phase, the exotic scale insect disperses through the forest, causing scale-induced alterations to patches of bark.
The killing front phase begins 1 to 19 years after the arrival of the scale. Throughout this phase, the scale-modified bark is killed and colonized by species of Neonectria, rendering the dead tissues vulnerable to additional decaying fungi. The resulting beech snap and mortality levels may reach 50 percent in 5 years. The final aftermath forest phase results in an ecological accommodation to the disease, resulting in either a change in species composition or the death of re-emergent beech. The genetically identical stump sprouts and root suckers, which appear following the initial BBD deaths and/or salvage, die in a second wave of BBD. When there are few other stressors acting on the beech, the trees can live for many years with sub-lethal Neonectria infections and under conditions of multiple stressors such as drought, out of season frosts, and insect attacks the disease acts like a decline complex.
SIREX WOODWASP
Native to Europe, the sirex woodwasp (Sirex noctilio
Fabricius) is a forest pest that attacks pine trees,
particularly red pines (Pinus resinosa) and white pines
(Pinus strobus). Unlike native woodwasps, which only
attack dead and dying trees, sirex woodwasps attack living
trees, causing foliage to wilt and turn red or brown. The
female deposits a fungus in a tree when laying its eggs, and
the fungus can weaken and kill a tree within a few weeks.
Adult wasps are large, usually 1 to 1½ inches in length, with
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a spear-shaped plate at the tail end. They are difficult to distinguish from native wasps. Sirex
woodwasps have been successfully controlled using parasitic nematodes that infect the wasps’
larvae and ultimately sterilize the adult females.
ASIAN AMBROSIA BEETLE
The Asian ambrosia beetle (Xyleborinus saxeseni),
introduced to the United States in the 1970s, feeds on
a variety of hardwood plants including oak, elm,
cherry, buckeye, and magnolia trees. Adult beetles are
about the size of a pin head, with females around 2 to
3 mm long, and males about 1.5 mm long. They are
dark reddish brown and have a stout, hunched appearance. Infestations are detectable by a 2-
to 3-inch long spine of boring dust that protrudes from the stem of a plant. This spine is
created as the female excavates the gallery she has bored into the plant. Plants infested by
these beetles should be removed and burned. Insecticide application to the trunks of
surrounding plants may help control infestation.
GYPSY MOTH
Gypsy moth (Lymantria dispar) was first brought to the
United States in the 1860s to aid in silk production.
Since then the moths have defoliated large swaths of
forest, moving as far westward as Minnesota.
Populations reach outbreak levels every 5 to 10 years.
Although the caterpillars feed on the leaves of more
than 300 species, they prefer oak, apple, alder,
basswood, birch, hawthorn, poplar, sweet gum, and
willow. Adult moths live only a week and do not feed.
Caterpillars have five pairs of blue spots followed by six pairs of red spots. A thin yellow stripe
runs along the middle of their backs. Gypsy moth has been controlled naturally through various
means, including a disease-causing fungus, a virus, and a ground beetle that eats gypsy moth
caterpillars.
THOUSAND CANKERS DISEASE
Dieback and mortality of eastern black walnut (Juglans nigra) in several Western States have become more common and severe during the last decade. A tiny bark beetle is creating numerous galleries beneath the bark of affected branches, resulting in fungal infection and
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canker formation. The large numbers of cankers associated with dead branches suggest the disease’s name—thousand cankers disease.
The principal agents involved in this disease are a newly identified fungus (Geosmithia) and the walnut twig beetle (Pityophthorus juglandis). Both the fungus and the beetle only occur on walnut species. An infested tree usually dies within 3 years of initial symptoms.
A number of factors enabled this disease to establish itself in eastern forests: the widespread distribution of eastern black walnut, the susceptibility of this tree species to the disease, and the capacity of the fungus and beetle to invade new areas and survive under a wide range of climatic conditions in the West. Thousand Cankers Diseases has recently been identified in eastern PA.
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PART 4:
Appendices
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APPENDIX A: TREE EXPERTS CONSULTED
Mark Whitmore, [email protected], (607) 280-4064 Forest Entomologist, Department of Natural Resources, Cornell University
David L. Roberts, Ph.D., [email protected], (517) 355-4518
College of Agriculture and Natural Resources, Michigan State University Dr. William L. MacDonald, [email protected], (304) 293-8818
Professor, Division of Plant & Soil Sciences, West Virginia University Dr. Walter Carson, [email protected], (412) 624-5496
Associate Professor, University of Pittsburgh Thomas J. Hall, Ph.D., [email protected], (717) 948-3947
PA Bureau of Forestry, Plant Pathologist/Forest Pathologist, Pest Management Houping Liu, PhD, [email protected], (717) 948-3946
Forest Entomologist, PA DCNR, Bureau of Forestry, Pest Management David Schmit, [email protected], (717) 514-6703
Forest Health Specialist, PA DCNR Sandy Feather, [email protected], (412) 473-2540
Extension Educator, Commercial Horticulture, Penn State Cooperative Extension
APPENDIX B: NATIVE TREES AND RELATED THREATS
Oaks (all species) Gypsy moth; drought; oak wilt; bacterial leaf scorch; red oak decline;
white oak decline; P. ramorum (SOD); oak leaftier
Maples (all species)
Forest tent caterpillar; anthracnose; Asian long-horned beetle; sugar
maple decline; fall cankerworm; elm spanworm; drought; acid
precipitation
Eastern hemlock Hemlock woolly adelgid; elongate hemlock scale; drought; Fabrella
needle cast
Ash (all species) Emerald ash borer; ash yellows; ash decline; drought; fall cankerworm
American beech Beech bark disease (scale insect, exotic and native Neonectria
cankers); drought; elm spanworm
Walnut, butternut,
and elm
Thousand cankers disease & walnut twig beetle; butternut canker; elm
yellows and Dutch elm disease
Pines (white, red,
other Pinus spp.)
Sirex woodwasp; common pine shoot beetle; Orthotomicus erosus
(Mediterranean pine engraver); Ips pini; other exotic bark beetles;
drought
0
10
20
30
40
50
60
70
F H R S PARKS TOTAL
Trees & Shrubs Native To Pennsylvania: Percent by Park
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APPENDIX C: TREE SPECIES AND FREQUENCY BY PARK, FROM NATURAL AREAS STUDY 2010
Species Frick Highland Riverview Schenley Sugar maple 20,800 4,960 6,403
Norway maple 10,400 36,284 16,864 2,134
Elm 5,200 5,404 1,984 7,114
Black cherry 4,550 6,948 7,936 14,229
Northern red oak 4,550 2,316 4,960 5,691
Black locust 4,550 10,671
American beech 2,600
Crabapple 2,600
Green ash 1,950
Mulberry 1,300 2,134
Boxelder 650 711
Silver maple 650
Tree of heaven 650 1,544 19,920
Hickory 650 1,423
Hackberry 650 3,557
Hawthorn 650 992 9,960
White ash 650 2,316 2,976 45,531
Honeylocust 650 1,423
Sycamore 650
Callery pear 650
Oak species 650
White oak 650 3,860 2,846
Northern pin oak 650 2,316 2,976 1423 2,134
Locust species 650
Sassafras 650
Dogwood 1,544
Red maple 772 1,423
Alder 772
Serviceberry 772
Black walnut 772
Sweetgum 772
Magnolia 772
Spruce 772
Willow oak 772
Eastern hophornbeam 2,976 2,134
Spicebush 1,984 1,423
Chinkapin 992
Eastern redbud 992
Ginkgo 992
Black oak 992
Yellow buckeye 3,557
Witch hazel 3,557
European linden 3,557
Sycamore maple 711
Devil’s walking stick 711
Paulownia 711
Birch 711
Honeysuckle 711
Viburnum 711
Dead tree 3,088 5,952 14,229
Total 68,250 71,796 58,528 174,300
Total Number of Park Trees on 900 Acres 372,874
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APPENDIX C (CONTINUED): TREE SPECIES BY DENSITY, FROM NATURAL AREAS STUDY 2010
Norway maple 17.6 Dogwood 0.4
White ash 13.8 Boxelder 0.4
Black cherry 9.0 Chinkapin 0.3
Sugar maple 8.6 Eastern redbud 0.3
Dead tree 6.2 Ginkgo 0.3
Tree of heaven 5.9 Black oak 0.3
Elm 5.3 Alder 0.2
Northern red oak 4.7 Serviceberry 0.2
Black locust 4.1 Black walnut 0.2
Hawthorn 3.1 Sweetgum 0.2
White oak 2.0 Magnolia 0.2
Pin oak 1.8 Spruce 0.2
Eastern hophornbeam 1.4 Willow oak 0.2
Hackberry 1.1 Maple 0.2
Yellow buckeye 1.0 Devils walking stick 0.2
Witch hazel 1.0 Birch 0.2
European linden 1.0 Honeysuckle 0.2
Mulberry 0.9 Royal paulownia 0.2
Spicebush 0.9 Viburnum 0.2
Northern pin oak 0.7 Silver maple 0.2
American beech 0.7 Honeylocust 0.2
Crabapple 0.7 Sycamore 0.2
Red maple 0.6 Callery pear 0.2
Hickory 0.6 Oak 0.2
Locust 0.6 Sassafras 0.2
Green ash 0.5
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APPENDIX D: INSECTICIDES EFFECTIVE IN CONTROLLING EAB
Insecticide Formulation Active Ingredient Application Method Recommended Timing
Merit® (75WP,75WSP,2F) Imidacloprid Soil injection or drench Mid-fall and/or mid- to late spring
XytectTM (2F,75WSP) Imidacloprid Soil injection or drench Mid-fall and/or mid- to late spring
IMA-jet® Imidacloprid Trunk injection Early May to mid-June
Imicide® Imidacloprid Trunk injection Early May to mid-June
TREE-ägeTM
Emamectin benzoate Trunk injection Early May to mid-June
The City and PPC recognize that there are other effective insecticides that can be used to
control EAB. However, those insecticides are not listed here because they require overhead
spraying operations which potentially expose the applicator, park visitors, and the environment
to large quantities of diluted insecticides. The team feels that targeted injections of Emamectin
benzoate into either the cambium or the root system of the treated tree is the most effective
means of control.
It should also be noted that Imidacloprid is being studied to see if a link exists between the
chemical and bee colony collapse. If a link is documented by the scientific community
researching the topic, Imidacloprid will be removed from the list of tools used to combat EAB.
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APPENDIX E: TREE SPECIES PLANTED IN THE PITTSBURGH CITY PARK WOODLANDS
Early Successional
Dry to Mesic
Black cherry
Grey birch
Quaking aspen
Big leaved aspen
Black locust
Red pine
Virginia pine
Pitch pine
Eastern red cedar
Smooth sumac
Staghorn sumac
Devil’s walking stick
Pin cherry
Flowering dogwood
Mesic
Striped maple
Red mulberry
Black walnut
White pine
Riparian
Sycamore
Silver maple
Cottonwood
Mid Successional
Dry
Black gum
Persimmon
Hop hornbeam
Chestnut Oak
Dwarf chestnut oak
Sassafras
Mesic
Cucumber tree
Red maple
Basswood
Tulip poplar
Sweet birch
Pignut hickory
Shagbark hickory
Mockernut hickory
Bitternut hickory
White oak
Sweet gum
Riparian / Wetland
Swamp White Oak
Bur oak
Pawpaw
Ohio buckeye
Late Successional
Dry
Sugar maple
Mesic
American beech
Eastern hemlock
Yellow Birch
Musclewood
Riparian
Yellow buckeye
Shrubs – incomplete list
Carolina rose
Lowbush blueberry
Highbush blueberry
Sourwood
Spicebush
Hazelnut
Blackhaw
Grey dogwood
Alternate leaved dogwood
Bladdernut
Allegheny serviceberry
Black chokeberry
Washington hawthorn
APPENDIX F: PHOTO CREDITS
Asian Long-Horned Beetle: Pest and Diseases Image Library, Bugwood.org
Sirex woodwasp: Vicky Klasmer, Instituto Nacional de Tecnologia Agropecuaria, Bugwood.org
Asian ambrosia beetle: Pennsylvania Department of Conservation and Natural Resources - Forestry Archive,
Bugwood.org
Gypsy moth: Ferenc Lakatos, University of West-Hungary, Bugwood.org
Hemlock woolly adelgid, Connecticut Agricultural Experiment Station Archive, Connecticut Agricultural Experiment
Station, Bugwood.org