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

2012 ACTION PLAN FOR PARK TREES

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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

http://semircd.org/ash/news/UrbanWoodUsePLanningWorksheet.pdf

http://semircd.org/ash/news/Cost%20Effective%20Tree%20Removal.pdf

http://www.ci.olympia.wa.us/NR/rdonlyres/8825122E-5317-4DBC-9611-B3FA697160A4/0/WoodWasteRecyclingReport.pdf

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.

http://www.emeraldashborer.info/files/EAB-FieldRelease-Guidelines2010.pdf


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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


26 | P a g e

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


27 | P a g e

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

mailto:[email protected]

http://www.msue.msu.edu/workspaces/external.cfm?workspace_id=-4&object_type=user&object_id=112044


http://www.wvagriculture.org/WVAFHF/10MacDonaldBio.pdf


http://www.pitt.edu/~biohome/Dept/Frame/Faculty/carson.htm






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

Documents

Pittsburgh Park Trees Action Plan