United States Department of Agriculture

Forest 

Service

General Technical 

Report NRS-139

Northern 

Research Station September 2014

Monitoring Ash (Fraxinus spp.) 

Decline and Emerald Ash Borer 

(Agrilus planipennis) Symptoms 

in Infested Areas

Kathleen S. Knight

Britton P. Flash

Rachel H. Kappler

Joel A. Throckmorton

Bernadette Grafton

Charles E. Flower
Visit our homepage at: http://www.nrs.fs.fed.us/

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September 2014 Email: nrspubs@fs.fed.us

Manuscript received for publication 18 October 2013

Abstract

Emerald ash borer (A. planipennis) (EAB) has had a devastating effect on ash (Fraxinus) 

species since its introduction to North America and has resulted in altered ecological 

processes across the area of infestation. Monitoring is an important tool for understanding 

and managing the impact of this threat, and the use of common methods by the many groups 

engaged in monitoring increases the value of monitoring data. We provide detailed methods 

for monitoring populations of ash trees, emerald ash borers, and lingering ash trees. These 

comprehensive methods can assist ecologists and managers in understanding the dynamics 

and effects of EAB infestations. Choice among these methods depends on the scientific and 

policy questions of interest and the stage of infestation being monitored.

Cover Photo

Researcher Rachel Kappler measures an ash tree. Photo by Rachel Hefflinger, The Ohio State 

University

The Authors

Kathleen S. Knight is a research ecologist and Britton P. Flash and Charles E. Flower are 

biological aides, U.S. Forest Service, Northern Research Station, Delaware, OH.

Rachel H. Kappler, Joel A. Throckmorton, and Bernadette Grafton are research associates, 

The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH.

The use of trade, firm, or corporation names in this publication is for the information and 

convenience of the reader. Such use does not constitute an official endorsement or approval 

by the U.S. Department of Agriculture or the Forest Service of any product or service to the 

exclusion of others that may be suitable. 
1

INTRODUCTION

Before the invasion of emerald ash borer (EAB, Agrilus 

planipennis Fairmaire), ash trees (Fraxinus spp.) were 

widely distributed across temperate forests in the eastern 

United States, reaching their highest densities in the 

Great Lakes region (Flower et al. 2013a). In Ohio alone, 

there are estimates of ~3.8 billion ash trees representing a 

significant component of the forest composition (Herms 

et al. 2004). Within the past 10 years, the invasive 

beetle has devastated eastern deciduous forests, killing 

billions of ash trees, subsequently changing the species 

composition, structure, and associated functions of these 

ecosystems (Flower et al. 2013a). The insect’s devastation 

of regional forests and urban plantings is costing up to 

an estimated $18 billion due to reductions in land value, 

removal of dead ash trees, and tree replacement (Kovacs 

et al. 2010, Sydnor et al. 2007). With such drastic and 

immediate impacts, monitoring ash decline and assessing 

the effects of EAB is vital when prescribing a course of 

action that will mitigate the ecological and economic 

effects. Monitoring data can give land managers baseline 

information that may assist them in timing management 

activities such as hazard tree removal, invasive plant 

removal, and re-planting of desirable tree species.

EAB is likely to have both short-term and long-term 

effects on ecosystem dynamics. To quantify and better 

understand the full impacts of EAB, data describing levels 

of EAB infestation and its effects on ash populations 

may be coupled with current data on forest ecosystems. 

A cascade of ecological effects may result from the 

successional and structural changes triggered by ash 

mortality (Gandhi and Herms 2010). Previous studies 

show that gaps potentially lead to a release of shade 

tolerant species and influx of invasive species, both 

of which may alter the successional trajectory of the 

forest (Gandhi and Herms 2010). U.S. Forest Service 

researchers have developed and deployed the methods 

presented here to answer questions directly related to 

EAB population dynamics, ash tree mortality, tree fall, 

and forest responses. Information collected from the 

monitoring approach presented here can confirm EAB 

presence and density, which can help inform landowners 

regarding the appropriate management approach. For 

instance, by measuring EAB densities and patterns of tree 

mortality, Knight et al. (2008) revealed that individual 

ash trees can decline from healthy to dead in as little as 

2 years in forests with high EAB densities, threatening 

public safety because of the increased potential of 

tree falls. Furthermore, such a monitoring approach 

can reveal the magnitude of the potential ecological 

consequences, which remain largely uninvestigated.

Recent studies have shown the immediate impacts of 

EAB on ash mortality and have investigated how ash 

population dynamics are altered by this invasive pest 

(Flower et al. 2013a, Gandhi and Herms 2010, Klooster 

et al. 2013, Knight et al. 2013). A recent study in 

southeastern Michigan observed EAB-induced mortality 

of greater than 99 percent for ash trees and saplings over 

2.5 cm d.b.h. (diameter at breast height, 1.37 m) (Herms 

et al. 2010). Despite this extreme mortality rate, the 

established seedlings persisted because EAB cannot infest 

seedlings and small saplings. The seed bank, however, 

declined because few parent trees survived, resulting 

in little ash regeneration in these areas (Klooster et al. 

2013). Herms et al. (2010) found that EAB continued 

to remain at low levels in these areas, suggesting that 

the borer may infest the ash trees as soon as they reach a 

sufficient size.

To better understand the resistance of ash populations 

to EAB, lingering ash trees have been monitored, 

propagated, and tested (Knight et al. 2012, Koch et al. 

2012). The term lingering ash describes a healthy ash tree 

of >10 cm d.b.h. existing in a site that is known to have 

been infested for several years and where >95 percent 

of trees have already died. Surveys conducted in 2010 

and 2011 at Indian Springs Metro Park in southeastern 

Michigan and Oak Openings Preserve Metro Park in 

northwestern Ohio indicated similar patterns of decline 

and survival (Knight et al. 2012). Of the lingering ash 

trees that were healthy in 2010, 74 and 78 percent 

remained healthy in 2011 at Oak Openings and Indian 

Springs, respectively (Knight et al. 2012). Individuals 

that were in decline in 2010 continued to follow this 

degenerating trend in 2011. It is necessary to continually 

monitor the lingering ash while EAB populations remain 

at low levels surrounding these sites in order to determine 

trees that may exhibit rare resistance or tolerance to this 

pest (Knight et al. 2012). Understanding these dynamic 
2

interactions and trends will help managers observe the 

trajectory of EAB spread.

We recommend using the ecological monitoring methods 

presented here to assess EAB-induced ash tree decline and 

plant community responses, determine EAB population 

dynamics, and track lingering ash populations after EAB 

has killed >95 percent of the large ash trees. We report 

here methods developed and tested over a decade of 

long-term monitoring and research efforts that provide a 

framework that can be used throughout the entire region 

of EAB infestation. We seek to provide researchers and 

managers with a standardized methodology that can 

help them collect information they need to manage the 

numerous issues associated with introduced forest pests. 

Many users will want to choose a subset of our methods, 

selecting those measures most closely linked to the goals 

of their monitoring program and to the experience and 

skills of their monitoring teams. This report describes 

three procedures for assessing EAB infestation and effects 

on ash populations: ash monitoring plots, EAB traps, and 

lingering ash surveys.

ash MONITORING PLOT METHODS

Ash monitoring plots can be used either in the short 

term, to get a snapshot of ash tree health, EAB 

symptoms, and species composition, or in the long 

term, to further understand the temporal effects of EAB 

on forests. The effects of EAB have previously been 

quantified using field or monitoring plots, by estimating 

ash canopy dieback, and counting D-shaped exit holes 

and woodpecker attacks on areas of infestation (Smith 

2006). Flower et al. (2013a) successfully used these 

methods to quantify the impacts of EAB on non-ash tree 

growth and forest carbon uptake. Although recording 

EAB symptoms of Fraxinus spp. is the primary focus 

of the monitoring plots, this approach may be adapted 

to quantify the presence of invasive plants, plant cover, 

seedling density, overstory tree growth, and the resulting 

changes in canopy openness.

We recommend establishing a minimum of three plots 

in each forest stand (area of the forest with relatively 

homogeneous composition) and using large main plots 

to measure larger trees and nested smaller subplots and 

microplots to measure saplings and seedlings, respectively 

(Fig. 1). In our study design, each circular large 

main plot has an area of 400 m2 (11.28-m radius) for 

monitoring ash trees ≥10 cm d.b.h. Observations of other 

tree species of the same size class may also be conducted 

within the main plot. Ash saplings taller than 1.37 m 

and <10 cm d.b.h. are measured within a nested subplot 

centered in the plot (8-m radius; 200 m2

); saplings and 

shrubs of other taxa may also be counted within the 

subplot. Surveying trees in a systematic order facilitates 

identification of individual trees between years without 

needing to tag each tree. For example, we begin in the 

north and move clockwise around the plot (as viewed 

from the center). Because the subplot is similar in size to 

the Forest Inventory and Analysis (FIA) subplot (U.S. 

Forest Service 2011a), FIA methods such as canopy cover 

by layer (U.S. Forest Service 2011b) may also be used 

in the subplot if desired. Depending on the goals of the 

study, data collected for each ash tree and sapling may 

include d.b.h., ash canopy condition rating, common 

symptoms, crown class, crown ratio, dead tree breakup, 

and dead tree fall. These measurements are described in 

detail below and an example data sheet is included in 

Appendix 1.

Figure 1. 

Figure 1.—A diagram of the EAB monitoring plot with a large 

main plot, nested subplot, and four microplots.
3

For the surveillance of ash seedlings less than 1.37 m 

tall, four microplots (each 1.13-m radius; 4 m2

) are 

placed 6 m from plot center in each cardinal direction. 

Studies that require the inclusion of herbaceous plants, 

shrubs, and seedlings of other taxa may follow the same 

microplot procedure for these counts.

Ash Canopy Condition Rating

Ash trees tend to thin and die back as they are attacked 

by EAB (Flower et al. 2013b, Smith 2006). Ash trees 

experience water and nutrient stress as EAB larvae feed 

and create galleries. These galleries correlate with visible 

loss of canopy, as assessed by a user-friendly ash canopy 

condition rating system (Flower et al. 2013b). The 

canopy condition rating scale (Table 1, Fig. 2, Smith 

2006), is used to record the health of each ash tree and 

sapling as infestation progresses. Dieback is defined as 

dead twigs (without leaves). Only consideration of the 

sun-exposed branches is necessary, because shedding may 

naturally occur on shaded or suppressed branches. If 

possible, it is best for two people to view each tree from 

different angles and reach consensus on a canopy rating. 

These ash canopy condition rating classes correlate with 

more general measures of tree canopy health used by FIA 

(Royo et al. 2012); however, they are more specific to 

the decline progression of EAB-infested ash trees (Smith 

Figure 2.—The ash canopy condition rating scale is used to categorize ash canopies in different stages of decline. 

The numbers on the right side of the page correspond to ratings listed in Table 1. (Figure 2 continued on page 3.)

1

2
4

3

4

5

Figure 2.—continued. Photo line 1-left by Kevin Rice, Penn 

State University; all other photos by Kathleen Knight, U.S. 

Forest Service.
5

2006). While not a symptom of EAB, the presence of 

seeds is often noted to facilitate future collection of 

seeds. For more information on ash seed collection, see 

Knight et al. (2010 a, b).

Common Symptoms

Common EAB symptoms are recorded for each ash 

tree and sapling to indicate the degree of stress and 

severity of infestation within an individual tree. EAB 

exit holes are D-shaped and show where adults have 

emerged (Fig. 3); these are the only external symptoms 

that are specific to EAB. However, they are often seen 

only late in the infestation process (Cappaert et al. 

2005). If the bark is peeling off the tree, serpentine 

galleries beneath the bark are also specific to EAB 

(Fig. 4). Other symptoms assessed may be associated 

with EAB but are also found on stressed ash trees that 

are not necessarily infested. Other problems that can 

cause these symptoms include ash yellows, native beetle 

infestation, and ash decline syndrome (Michigan State 

University 2005, Sinclair and Lyon 2005). EAB is 

a food source for woodpeckers; prolific woodpecker 

feeding is often evident in EAB-infested trees (Smith 

2006) (Fig. 5). Epicormic and basal shoots typically 

develop as a result of dieback in the bole (Figs. 6, 7). As 

larvae feed on the phloem, the tree produces lignified 

calluses (Knight, personal observation). This increased 

surface area causes splitting in the bark, which 

sometimes allows viewing of the EAB gallery inside the 

tree (Fig. 5).

Table 1.—Ash canopy condition rating scale used to quantify degree of decline and dieback of 

ash trees (Fraxinus spp.)

Rating Description

1 Canopy is full and healthy

2 Canopy has started to lose leaves (thinning), but no dieback (dead top canopy twigs 

without leaves) is present

3 Canopy has less than 50% dieback

4 Canopy has more than 50% dieback

5 Canopy has no leaves, epicormic sprouts may be present on the trunk

Figure 3.—EAB adult exit hole and woodpecker hole on an 

ash tree. Photo by Kathleen Knight, U.S. Forest Service.

Figure 4.—EAB larval feeding galleries with characteristic 

“S” shape. Photo by Kathleen Knight, U.S. Forest Service.

EAB exit hole

Woodpecker hole
6

Crown Class

The qualitative classification system, known as 

“crown class,” describes the relative illumination of a 

tree’s canopy. Crown class is recorded as dominant, 

codominant, intermediate, or suppressed (Oliver and 

Larson 1996) (Table 2). Understanding the position 

of the ash trees in the canopy of a forest will assist in 

understanding the role of ash in the structure of the 

forest. Crown class affects ash mortality from EAB, with 

shaded trees (intermediate and suppressed) exhibiting 

more rapid mortality than trees with better light exposure 

(dominant and co-dominant) (Knight et al. 2013).

Crown Ratio

Crown ratio is the proportion of the height of the tree 

that has live foliage. In healthy trees, this correlates with 

the growth form of the tree, which may vary depending 

on the tree species, on whether the tree is open grown or 

surrounded by other trees, and on genetically determined 

traits. In stressed trees, it also relates to the amount 

of defoliation and dieback taking place due to stresses 

Figure 6.—Epicormic sprouts on an EAB-infested ash 

tree. Photo by Rachel Kappler, Bowling Green State 

University.

Figure 5.—Bark splitting with visible larval galleries, 

numerous woodpecker holes, and EAB exit hole on an ash 

tree trunk. Photo by Kathleen Knight, U.S. Forest Service.

Figure 7.—Basal sprouts on an EAB-infested ash tree. 

Photo by Kathleen Knight, U.S. Forest Service.

Woodpecker 

holes

Bark split
7

Tree and Sapling Data Checklist

• Tree species

• d.b.h.

• Ash canopy condition rating

For live ash trees, record:

• Crown class

• Crown ratio

• Note seed production

For dead ash trees, record:

• Breakup rating

• Tree fall

Between 1.25 and 1.75 m height on the 

trunk of each living or recently dead ash 

tree, record the number of:

• EAB holes

• Woodpecker holes

For each ash tree, record the presence/

absence of:

• Woodpecker feeding holes 

anywhere on the tree

• Epicormic and basal shoots

• Bark splitting

that may be related to EAB. It is a comparison of the 

length from the top of the live crown (not including 

top dieback) to the “obvious live base,” with respect to 

the tree’s total height (U.S. Forest Service 2011b), and 

recorded in categories of 10 percent.

Ash Breakup Rating and Fallen 

Category

After it dies, a tree continues to decay, impacting the 

forest’s structure and potentially creating a safety hazard, 

depending on the tree’s location. To understand how 

quickly the dead ash trees break apart and fall down, we 

developed a categorical rating system for canopy breakup 

(severity of breakup is rated A-E) (Table 3, Fig. 8). The 

fallen tree categories (Table 4) describe how the tree fell 

and how it interacts with surrounding tree species.

Table 2.—Crown class categories (Oliver and Larson 1996)

Category Description

Dominant Above general canopy of stand; receives 

direct sunlight on top and all sides

Codominant Average position in stand; receives direct 

sunlight on top and at least one side

Intermediate Below general canopy; receives direct 

sunlight on top

Suppressed Completely overtopped; receives no direct 

sunlight

Table 3.—Breakup categories used for dead ash trees

Rating Description

A All branches have fine twigs 

B >50% of branches have fine twigs

C ≤50% of branches have fine twigs

D No fine twigs, tertiary branches present

E Main stem and possibly primary or secondary 

branches present 

Table 4.—Fallen tree categories used in ash 

monitoring plots

Code Description

L Ash leaning

U Ash uprooted

SH Ash snapped high, above d.b.h.

SL Ash snapped low, below d.b.h.

F Non-ash tree has fallen on it

AF Ash tree has fallen on it

Seedling Data Checklist

• Seedling species

• Percent cover

• Number of new seedlings with 

colyledons

• Number of established seedlings 

<1.37 m tall
8

Figure 8.—The ash tree breakup rating 

scale is used to categorize the stages of 

branch loss of dead ash trees. The letters 

to the right of the photos correspond 

to the breakup categories in Table 3. 

Photos by Rachel Kappler, Bowling 

Green State University.

B

A

D

C

E
9

Seedling Data Collection

For collection of seedling data, a circular microplot with 

a radius of 1.13 m is placed 6 m from the plot center in 

each cardinal direction (Fig. 1). It is helpful to construct 

a frame to place in the microplot to visualize its radius 

and bounds. The number of new and established ash 

seedlings less than 1.37 m tall is recorded along with 

their percent cover. An example data sheet is included 

in Appendix 2. New seedlings are identified by their 

cotyledons (Fig. 9). We use the following percent cover 

classes: <1, 1, 2-5, 6-10, 11-20, 21-30, 31-40, etc. If 

relevant, microplots are used to record other plant species 

or as locations to measure canopy openness or other 

features of interest.

EAB TRAP METHODS

Visual signs of EAB presence can be difficult to detect 

in early stages of infestation. Currently, the best way to 

detect EAB before visual signs are apparent is to trap 

EAB adults using sticky purple prism traps containing 

a lure (Francese et al. 2008) (see Table 5 for vendors). 

These traps are made of corrugated plastic that is folded 

to make a triangular prism; each side is 36 by 60 cm. The 

sides are coated with TangleTrap®, a clear insect trapping 

glue that remains sticky throughout the summer. A 

spreader is used to hold the trap together and to attach 

a rope or hanger. The lure, usually a sponge sealed in 

a plastic pouch, is attached to the spreader. The lures 

contain concentrations of volatile compounds also found 

on ash bark and shown to be attractive to EAB (Crook 

et al. 2008). More recently, national survey programs 

have switched from traps painted the old shade of purple 

termed “standard purple” or “Coroplast purple” to a new 

shade of purple termed “TSU purple” or “Sabic purple,” 

which has been shown to increase attractiveness to EAB 

(Francese et al. 2010). Survey programs have also begun 

to use a (Z)-3-hexenol lure (Crook et al. 2012, Grant et 

al. 2011) in addition to the manuka oil lures to enhance 

attractiveness to EAB (USDA APHIS PPQ 2013). 

Figure 9.—New green ash seedlings, 

germinated in the current year, can 

be identified by their cotyledons. 

Photo by Kathleen Knight, U.S. 

Forest Service.

Table 5.—Trap supply resources

Items Supplier

Lures, traps, and 

hangers

Synergy Semiochemicals Corp., Box 

50008 South Slope RPO, Burnaby, 

British Columbia, Canada. http://www.

semiochemical.com/html/eab_trapping.

html#top

Pre-glued purple 

prism traps

Great Lakes IPM, Inc., 10220 E Church 

Rd., Vestaburg, MI, USA; 800-235-0285; 

http://www.greatlakesipm.com

Metal spreaders and 

hangers

Midwest Wire Products Ltd., 649 S. 

Lansing Ave., Sturgeon Bay, WI, USA; 

800-445-0225 , ext 124; http://www.

wireforming.com

Sling shot, throw 

line, and throw bags

Sherrill Tree, 200 Seneca Rd., 

Greensboro, NC, USA; 800-525-8873; 

http://www.sherrilltree.com
10

EAB Traps Data Checklist

• Trap tag number

• GPS coordinates

• Date trap was set

• Date lure was replaced

• Date trap was removed

• Ash species

• Ash tree d.b.h.

• Ash canopy condition rating

• Number of EAB at re-lure date

• Number of EAB at removal date

Safety, cost, and efficacy should all be considered when 

determining which traps and lures to use in a research 

or monitoring study. For example, when the goal is 

to detect new infestations, it may be beneficial to use 

the most attractive traps and lures. When the goal is to 

monitor relative EAB density over time in areas known 

to be infested by EAB, cheaper and safer options that 

are less attractive may be acceptable. Manuka oil lures 

with “standard purple” traps have performed well for this 

purpose.

At least four traps should be hung at each forest location 

per year. The traps are hung in living ash trees ≥10 cm 

d.b.h., preferably along the forest edge or in an open 

area close to an ash woodlot (Francese et al. 2008). If 

no other trees are available, smaller ash trees or lingering 

ash may be used. The GPS coordinates, ash species, 

d.b.h., and canopy condition rating are recorded. There 

are many methods to hang traps, which are described 

along with trap assembly details in USDA APHIS 

PPQ (2008). To hang traps high in the canopy of ash 

trees, the preferable method is the rope method, using 

a forester’s sling shot, a throw line, 3/16 inch braided 

nylon rope, and a 14-ounce throw bag. For more 

information about the use of these tools and associated 

safety protocols, see Knight et al. (2010 a, b). The weight 

is attached to the throw line and the sling shot is used 

to shoot the weight over an ash tree branch. The branch 

chosen should be at least halfway up the tree or ~13 m 

off the ground and tested to be sturdy (Francese et al. 

2008). The nylon rope is attached to the throw line and 

pulled over the branch; each end of the nylon rope is 

then attached to the trap spreader. The trap is pulled up 

into the tree and the excess rope is tied around the tree 

trunk at chest height.

We recommend putting the traps up in May or June 

just before reaching 450 growing degree days (base 50° 

F) (USDA APHIS PPQ 2013). Studies have shown first 

emergence of EAB at 450-670 GDD (base 50° F) in 

April-June (Cappaert et al. 2005, Discua 2013). Adults 

feed on ash foliage, on average, for 5 to 7 days before 

mating; females feed an additional 5 to 7 days before 

oviposition. Multiple matings can occur; however, 

beetles survive for only 3 to 6 weeks after emergence 

(Bauer et al. 2004, Cappaert et al. 2005, Lyons et al. 

2004). Manuka oil lures are effective for 60 days and 

then must be replaced. We recommend counting EAB 

on the traps during re-luring, because insects can fall off 

if the trap is later damaged. The traps are taken down in 

August to count the number of adult EAB. Example data 

sheets for traps are included in Appendix 3.

LINGERING ASH SURVEY

To investigate ash trees that may be resistant or tolerant 

to EAB infestation, any naturally occurring ash tree 

still alive after the initial die off should be surveyed. 

Example data sheets are included in Appendix 4. To 

avoid investigating trees that are simply the last to die, we 

suggest observing a threshold of 2 years after >95 percent 

mortality occurs. Lingering ash must be a sufficient size 

to ensure they were large enough for EAB to infest during 

the peak of the infestation. EAB infests ash trees as small 

as 2.5 cm d.b.h. However, ash species have the capacity 

for rapid growth and may rapidly attain a much larger 

size after the infestation passes through. For this reason, 

we recommend surveying trees ≥10 cm d.b.h. Tagging 

each tree as well as using a global positioning device will 

assist with future surveillance. The data collected for the 

lingering ash are very similar to that collected for ash in 

monitoring plots.
11

Lingering Ash Tree Data Checklist

• GPS coordinates

• Tree species

• Tag number

• d.b.h.

• Ash canopy condition rating

For live ash trees, record:

• Crown class

• Crown ratio

• Note seed production

For dead ash trees, record:

• Breakup rating

• Tree fall

Between 1.25 and 1.75 m height on the 

trunk of each living or recently dead ash 

tree, record the number of:

• EAB holes

• Woodpecker holes

For each ash tree, record the presence/

absence of:

• Woodpecker feeding holes anywhere 

on the tree

• Epicormic and basal shoots

• Bark splitting

SAFETY

In addition to the typical hazards associated with outdoor 

research, studying EAB in forest ecosystems may involve 

researchers collecting data in forest stands with standing 

dead trees. Dead trees are a hazard, because they can 

fall or drop limbs without warning. It is important for 

researchers to wear hard hats, avoid going out on windy 

days, and be aware of their surroundings at all times.

ACKNOWLEDGMENTS

The Forest Service’s Northern Research Station, the 

National Research Initiative, and the Animal and Plant 

Health Inspection Service of the U.S. Department of 

Agriculture support this methods development research. 

We thank R. Long, J. Rebbeck, D. Herms, and A. 

Smith, who collaborated with us to develop these 

research methods. We also thank S. Stout, S. Hiremath, 

J. Lorenz, and S. McKenney for reviewing this report.

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Liu, H. 2004. Emerald ash borer life cycle. In: 

Mastro, V.; Reardon, R., comps. Proceedings of 

the emerald ash borer research and technology 

development meeting; 2003 September 30 - October 

1; Port Huron, MI. FHTET 2004-02. Morgantown, 

WV: U.S. Department of Agriculture, Forest Service, 

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Cappaert, D.; McCullough, D.G.; Poland, T.M.; 

Siegert, N.W. 2005. Emerald ash borer in North 

America: a research and regulatory challenge.

American Entomologist. 51(3): 152-165.

Crook, D.J.; Khrimian, A.; Cossé, A.; Fraser, I.; 

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(Coleoptera: Buprestidae). Journal of Economic 

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Discua, S.A. 2013. Characterizing prepupal diapause 

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12

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female emerald ash borer (Coleoptera: Buprestidae) 

responses to phoebe oil and (Z)-3-hexenol lures 

in light green prism traps. Journal of Economic 

Entomology. 104(1): 173-179.

Herms, D.A.; Klooster, W.; Knight, K.S.; Gandhi, 

K.J.K.; Herms, C.P.; Smith, A.; McCullough, D.G.; 

Cardina, J. 2010. Ash regeneration in the wake of 

emerald ash borer: Will it restore ash or sustain 

the outbreak? In: Lance, D.; Buck, J.; Binion, 

D.; Reardon, R.; Mastro, V., comps. Proceedings 

of the emerald ash borer research and technology 

development meeting; 2009 October 20-21; 

Pittsburgh, PA. FHTET-2010-01. Morgantown, WV: 

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Health Technology Enterprise Team: 18-19.

Herms, D. A.; Stone, A.K.; Chatfield, J.A. 2004. 

Emerald ash borer: the beginning of the end of 

ash in North America? In: Chatfield, J.A.; Draper, 

E.A.; Mathers, H.M.; Dyke, D.E.; Bennett, P.J.; 

Boggs, J.F., eds. Ornamental plants: annual reports 

and research reviews 2003. Wooster, OH: Ohio 

Agricultural Research and Development Center, The 

Ohio State University: 62-71.

Klooster, W.S.; Herms, D.A.; Knight, K.S.; Herms, 

C.P.; McCullough, D.G.; Cardina, J. 2014. Ash 

(Fraxinus spp.) mortality, regeneration, and 

seed bank dynamics in mixed hardwood forests 

following invasion by emerald ash borer (Agrilus 

planipennis). Biological Invasions. 16: 859-873.

Knight, K.S. 2010a. Ash seed collection: slingshot 

method. Gen. Tech. Rep. NRS-70. Newtown Square, 

PA: U.S. Department of Agriculture, Forest Service, 

Northern Research Station. [Video; 4:08 min. in 

length].

Knight, K.S.; Brown, J.P.; Long, R.P. 2013. Factors 

affecting the survival of ash (Fraxinus spp.) trees 

infested by emerald ash borer (Agrilus planipennis).

Biological Invasions. 15: 371-383.

Knight, K.S.; Herms, D.; Plumb, R.; Sawyer, E.; Spalink, 

D.; Pisarczyk, E.; Wiggin, B.; Kappler, R.; Menard, 

K. 2012. Dynamics of surviving ash (Fraxinus

spp.) populations in areas long infested by emerald 

ash borer (Agrilus planipennis). In: Sniezko, 

R.A.; Yanchuk, A.D.; Kliejunas, J.T.; Palmieri, 

K.M.; Alexander, J.M.; Frankel S.J., tech. coords. 

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the genetics of host-parasite interactions in forestry: 

disease and insect resistance in forest trees; 2011 July 

31-August 5; Eugene, OR. Gen. Tech. Rep. PSW240. Albany, CA: U.S. Department of Agriculture, 

Forest Service, Pacific Southwest Research Station: 

143-152.

Knight, K.S.; Karrfalt, R.P.; Mason, M.E. 2010b. 

Methods for collecting ash (Fraxinus spp.) seeds.
13

Gen. Tech. Rep. NRS-55. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern 

Research Station. 14 p.

Knight, K. S.; Long, R. P.; Rebbeck, J.; Smith, A.; 

Gandhi, K.; Herms, D. A. 2008. How fast will 

the trees die? A transition matrix model of ash 

(Fraxinus spp.) decline in forest stands infested 

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evaluating the relationship between FIA phase 3 

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pdf (Accessed July 28, 2014).
15

Appendix 1.—Example tree data (≥10 cm d.b.h. trees in 11.3 m radius plot, <10 cm d.b.h. ash trees in 8-m radius subplot)

Site Plot

Tree 

number Species

d.b.h. 

2011 

(cm)

Dead 

2011

Ash 

condition 

2011

d.b.h. 

2012 

(cm)

Ash 

condition 

2012

EAB exit 

holes 

2012

Woodpecker 

holes 2012 

(present - number)

Epicormic 

sprouts 

2012

Basal 

sprouts 

2012

Bark 

splits 

2012

Ash 

seeds 

2012

Canopy 

class 

2012

Crown 

ratio 

2012(%)

Dead 

2012

Dead tree 

breakup 

2012

Fallen 

category 

2012

OO2 3 1 Ulmus americana 13.8 N 13.8 Y

OO2 3 2 Acer saccharinum 48.7 N 49.5 C N

OO2 3 3 F. pennsylvanica 20.4 N 4 20.4 5 8 Y - 0 N N Y Y BOO2 3 4 F. pennsylvanica 3.6 N 1 3.8 1 0 N - 0 N N N N S 50 N

OO2 3 5 F. pennsylvanica 28.9 Y 5 28.9 5 N N N Y U

OO2 3 6 Ulmus americana 15.3 Y 15.3 Y

OO2 3 7 F. pennsylvanica 20.2 N 3 20.9 3 6 Y - 12 Y Y Y Y C 40 N

OO2 1 8 Acer saccharinum 32.3 N 33.4 C NOO2 3 8 F. pennsylvanica 15.9 N 1 16.8 2 0 Y - 0 Y N N N I 40 N

OO2 3 9 F. pennsylvanica 21.1 N 4 21.1 5 12 Y - 10 N Y Y Y A

OO2 3 10 F. pennsylvanica 20.0 N 1 20.3 3 7 Y - 5 Y Y Y N C 20 N

OO2 3 11 Populus deltoides 96.2 N 96.4 D N

OO2 3 12 F. pennsylvanica 16.0 N 2 16.7 2 8 Y - 10 Y Y Y Y S 60 N

OO2 3 13 Ulmus americana 16.5 N 16.9 I N

OO2 3 14 Ulmus americana 13.0 N 13.6 S N

OO2 3 15 Ulmus americana 25.0 N 26 C N

OO2 3 16 F. pennsylvanica 31.9 N 2 31.9 4 15 Y - 50 Y N Y N C 10 NOO2 3 17 F. pennsylvanica 24.7 N 1 24.9 3 30 Y - 5 Y N Y Y C 20 NOO2 3 18 F. pennsylvanica 4.2 N 1 5 1 2 Y - 0 N N Y N S 40 N
16

Appendix 2.—Example ash seedling data (seedlings <1.4 m tall in 4 m2 microplots)

Site Plot Microplot Species % Cover

Number of 

new

Number of 

established

OO2 1 N F. pennsylvanica 2-5 3 2

OO2 1 E F. pennsylvanica <1 2 0

OO2 1 E F. nigra 1-2 0 2

OO2 1 S F. pennsylvanica <1 1 0

OO2 1 W F. pennsylvanica <1 1 0

OO2 2 N F. pennsylvanica 11-20 2 4

OO2 2 E F. pennsylvanica 11-20 2 3

OO2 2 S F. pennsylvanica 6-10 0 3

OO2 2 S F. nigra 2-5 2 2

OO2 2 W F. pennsylvanica 6-10 2 2

OO2 3 N F. pennsylvanica 11-20 3 2

OO2 3 E F. pennsylvanica 11-20 0 4

OO2 3 S F. pennsylvanica 6-10 0 4

OO2 3 W F. pennsylvanica 6-10 0 3
17

Appendix 3.—Example EAB trap data

Site

Trap 

number Latitude Longitude Date Set

Date 

Re-lured

Date 

Removed Ash species d.b.h. (cm)

Ash 

condition

Number 

EAB at 

re-lure

Number 

EAB end of 

summer

FT1 1 41.5541 N 83.6961W 5/3/2012 7/1/2012 8/28/2012 F. pennsylvanica 20.5 3 2 2

FT1 2 41.554 83.695 5/3/2012 7/1/2012 8/28/2012 F. pennsylvanica 16.8 4 4 5FT1 3 41.555 83.694 5/3/2012 7/1/2012 8/28/2012 F. pennsylvanica 15.2 3 3 3FT1 4 41.555 83.693 5/3/2012 7/1/2012 8/28/2012 F. pennsylvanica 21.3 3 5 7

OO 1 41.682 83.666 5/3/2012 7/2/2012 8/27/2012 F. americana 17 4 80 85OO 2 41.682 83.667 5/3/2012 7/2/2012 8/27/2012 F. americana 13.1 4 106 110OO 3 41.687 83.671 5/3/2012 7/2/2012 8/27/2012 F. americana 10.8 3 67 67OO 4 41.689 83.672 5/3/2012 7/2/2012 8/27/2012 F. pennsylvanica 34.3 3 93 95
18

Appendix 4.—Example lingering ash dataSite Latitude Longitude Species

Tag 

number

d.b.h. 

2011

Dead 

2011

Ash 

condition 

2011

Ash 

condition 

2012

EAB exit 

holes 

2012

Woodpecker 

holes 2012 

(present - number)

Epicormic 

sprouts 

2012

Basal 

sprouts 

2012

Bark 

splits 

2012

Ash 

seeds 

2012

Canopy 

class 

2012

Crown 

Ratio 

2012(%)

Dead 

2012

OOFL 41.5708 N 83.8698 W F. pennsylvanica 1 15.3 N 1 1 0 N - 0 N N N N I 50 N

OOFL 41.5908 N 83.8700 W F. pennsylvanica 2 17.2 N 2 2 1 Y - 6 N N N Y I 60 NOOFL 41.6108 N 83.8702 W F. pennsylvanica 3 23.2 N 1 2 4 N - 0 Y N Y N C 40 NOOFL 41.6308 N 83.8704 W F. pennsylvanica 4 15.5 N 1 3 15 Y - 11 Y Y Y N I 30 NOOFL 41.6508 N 83.8703 W F. pennsylvanica 5 17.8 N 4 5 7 Y - 15 Y Y Y N 0 NOOFL 41.6708 N 83.8705 W F. pennsylvanica 6 20.7 N 4 5 8 Y - 12 Y Y Y N 0 NOOFL 41.6908 N 83.8710 W F. pennsylvanica 7 22.0 N 3 5 7 Y - 11 N Y Y N 0 YOOFL 41.7108 N 83.8710 W F. pennsylvanica 8 14.5 N 3 4 8 Y - 8 Y Y Y N S 10 NOOFL 41.7308 N 83.8702 W F. pennsylvanica 9 25.0 N 2 1 0 N - 0 Y N N Y C 70 NOOFL 41.7508 N 83.8700 W F. pennsylvanica 10 17.0 N 1 1 0 N - 0 N N N Y I 40 NOOFL 41.7708 N 83.8698 W F. pennsylvanica 11 16.6 N 3 4 7 Y - 9 Y Y Y N I 30 NOOFL 41.7908 N 83.8701 W F. pennsylvanica 12 19.2 N 2 2 5 Y - 1 N N N N C 70 NOOFL 41.8108 N 83.8700 W F. pennsylvanica 13 12.4 N 1 1 0 N - 0 N N Y N S 50 NOOFL 41.8308 N 83.8706 W F. pennsylvanica 14 11.6 N 2 2 0 N - 0 Y N Y N S 40 N
Printed on Recycled Paper

Knight, Kathleen S.; Flash, Britton P.; Kappler, Rachel H.; Throckmorton, Joel A.; 

Grafton, Bernadette; Flower, Charles E. 2014. Monitoring Ash (Fraxinus spp.) 

Decline and Emerald Ash Borer (Agrilus planipennis) Symptoms in Infested 

Areas. Gen. Tech. Rep. NRS-139. Newtown Square, PA: U.S. Department of 

Agriculture, Forest Service, Northern Research Station. 18 p

Emerald ash borer (A. planipennis) (EAB) has had a devastating effect on ash 

(Fraxinus) species since its introduction to North America and has resulted in altered 

ecological processes across the area of infestation. Monitoring is an important 

tool for understanding and managing the impact of this threat, and the use of 

common methods by the many groups engaged in monitoring increases the value 

of monitoring data. We provide detailed methods for monitoring populations of ash 

trees, emerald ash borers, and lingering ash trees. These comprehensive methods 

can assist ecologists and managers in understanding the dynamics and effects of 

EAB infestations. Choice among these methods depends on the scientific and policy 

questions of interest and the stage of infestation being monitored.

KEY WORDS: ash mortality, invasive species, lingering ash, ash canopy rating, dead 

tree breakup, prism trap, genetic resistance

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