Insecticide Options For Protecting Ash Trees From Emerald Ash Borer
Insecticide
Options for
Protecting
Ash Trees
from Emerald
Ash Borer
Daniel A. Herms
Deborah G. McCullough
David R. Smitley
Clifford S. Sadof
R. Chris Williamson
Philip L. Nixon
Insecticide Options for
Protecting Ash Trees from
Emerald Ash Borer
Daniel A. Herms1, Deborah G. McCullough2,
David R. Smitley3, Clifford S. Sadof4, R. Chris Williamson5,
and Philip L. Nixon6
1Professor, Department of Entomology, Ohio Agricultural Research and
Development Center, The Ohio State University, Wooster, OH 44691
2Professor, Department of Entomology and Department of
Forestry, Michigan State University, East Lansing, MI 48824
3Professor, Department of Entomology, Michigan
State University, East Lansing, MI 48824
4Professor, Department of Entomology, Purdue
University, West Lafayette, IN 47907
5Associate Professor, University of Wisconsin-Madison and University
of Wisconsin Cooperative Extension, Madison, WI 53706
6Extension Entomologist, Department of Natural
Resources and Environmental Sciences, University of
Illinois at Urbana-Champaign, Urbana, IL 61801
contents
Answers to Frequently Asked Questions . . . . . . . . . . . . . . . . . . . 3
What options do I have for treating my ash trees? . . . . . . . . 3
I know my tree is already infested with EAB .
Will insecticides still be effective? . . . . . . . . . . . . . . . . . . . . . 3
My ash tree looks fine but my county is quarantined
for EAB . Should I start treating my tree? . . . . . . . . . . . . . . . . . 4
I realize that I will have to protect my ash trees from
EAB for several years . Is it worth it? . . . . . . . . . . . . . . . . . . . . 4
Insecticide Options for Controlling EAB . . . . . . . . . . . . . . . . . . 5
Using Insecticides to Control EAB . . . . . . . . . . . . . . . . . . . . . . . 6
Soil-Applied Systemic Insecticides . . . . . . . . . . . . . . . . . . . . . 6
Trunk-Injected Systemic Insecticides . . . . . . . . . . . . . . . . . . . 7
Noninvasive, Systemic Basal Trunk Sprays . . . . . . . . . . . . . . . 7
Protective Cover Sprays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
How Effective Are Insecticides for Control of EAB? . . . . . . . . . . 8
Soil-Applied Systemic Insecticides . . . . . . . . . . . . . . . . . . . . . 8
Trunk-Injected Systemic Insecticides . . . . . . . . . . . . . . . . . . . 9
Emamectin benzoate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Imidacloprid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Noninvasive Basal Trunk Sprays with Dinotefuran . . . . . . . . 10
Protective Cover Sprays . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Key Points and Summary Recommendations . . . . . . . . . . . . . . 11
2
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
Insecticide Options for
Protecting Ash Trees from
Emerald Ash Borer
Emerald ash borer (Agrilus planipennis some sites, but the same treat-
Fairmaire), an invasive insect native to
ments failed in other sites . Further-
Asia, has killed tens of millions of ash
more, in some studies conducted
trees in urban, rural and forested settings .
over multiple years, EAB densities
This beetle was first discovered in 2002 in
continued to increase in individual
southeast Michigan and Windsor, Ontario . As trees despite annual treatment .
of June 2009, emerald ash borer (EAB) infes-
Some arborists have combined
tations were known to be present in 12 states treatments to increase the odds of
and two Canadian provinces . Many hom-
success (e .g ., combining a cover
eowners, arborists and tree care profession-
spray with a systemic treatment) .
als want to protect valuable ash trees from
EAB . Scientists have learned much about this
Our understanding of how EAB
insect and methods to protect ash trees since can be managed successfully
2002 . This bulletin is designed to answer
with insecticides has increased
frequently asked questions and provide
substantially in recent years . The
the most current information on insecticide
current state of this understanding
options for controlling EAB .
is detailed in the bulletin . It is important to
note that research on management of EAB
remains a work in progress . Scientists from
Answers to frequently
universities, government agencies and com-
Asked Questions
panies continue to conduct intensive studies
to understand how and when insecticide
treatments will be most effective .
What options do I have for treating my
ash trees?
I know my tree is already infested with
EAB. Will insecticides still be effective?
If you elect to treat your ash trees, there are
several insecticide options available and
If a tree has lost more than 50 percent of its
research has shown that treatments can be
canopy, it is probably too late to save the
effective . Keep in mind, however, that con-
tree . Studies have shown that it is best to
trolling insects that feed under the bark with
begin using insecticides while ash trees are
insecticides has always been difficult . This is
still relatively healthy . This is because most
especially true with EAB because our native
of the insecticides used for EAB control act
North American ash trees have little natural
systemically — the insecticide must be trans-
resistance to this pest . In university trials,
ported within the tree . In other words, a tree
some insecticide treatments were effective in
must be healthy enough to carry a systemic
Herms, McCullough, Smitley, Sadof, Williamson, Nixon
3
insecticide up the trunk and into the branches I realize that I will have to protect my
and canopy . When EAB larvae feed, their gal-
ash trees from EAB for several years. Is
leries injure the phloem and xylem that make
it worth it?
up the plant’s circulatory system . This inter-
feres with the ability of the tree to transport
The economics of treating ash trees with
nutrients and water, as well as insecticides . As insecticides for EAB protection are com-
a tree becomes more and more infested, the
plicated . Factors that can be considered
injury becomes more severe . Large branches
include the cost of the insecticide and
or even the trunk can be girdled by the larval
expense of application, the size of the trees,
galleries .
the likelihood of success, and potential
costs of removing and replacing the trees .
Studies have also shown that if the canopy of
Until recently, insecticide products had to
a tree is already declining when insecticide
be applied every year . A new product that
treatments are initiated, the condition of the
is effective for two years or even longer
tree may continue to deteriorate during the
(emamectin benzoate) has altered the eco-
first year of treatment . In many cases, the tree nomics of treating ash trees . As research pro-
canopy will begin to improve in the second
gresses, costs and methods of treating trees
year of treatment . This lag in the reversal of
will continue to change and it will be impor-
canopy decline probably reflects the time
tant to stay up to date on treatment options .
needed for the tree to repair its vascular
system after the EAB infestation has been
Benefits of treating trees can be more difficult
reduced .
to quantify than costs . Landscape trees typi-
cally increase property values, provide shade
My ash tree looks fine but my county
and cooling, and contribute to the quality of
is quarantined for EAB. Should I start
life in a neighborhood . Many people are sen-
treating my tree?
timental about their trees . These intangible
qualities are important and should be part of
Scientists have learned that ash trees with low any decision to invest in an EAB management
densities of EAB often have few or no exter-
program .
nal symptoms of infestation . Therefore, if
It is also worth noting that the size of EAB
your property is within a county that has been populations in a specific area will change
quarantined for EAB, your ash trees are prob-
over time . Populations initially build very
ably at risk . Similarly, if your trees are outside
slowly, but later increase rapidly as more
a quarantined county but are still within
trees become infested . As EAB populations
10-15 miles of a known EAB infestation, they
reach their peak, many trees will decline and
may be at risk . If your ash trees are more than die within one or two years . As untreated ash
15 miles beyond this range, it is probably
trees in the area succumb, however, the local
too early to begin insecticide treatments .
EAB population will decrease substantially .
Treatment programs that begin too early
Scientists do not yet have enough experi-
are a waste of money . Remember, however,
ence with EAB to know what will happen
that new EAB infestations have been discov-
over time to trees that survive the initial
ered every year since 2002 and existing EAB
wave of EAB . Ash seedlings and saplings are
populations will build and spread over time .
common in forests, woodlots, and right-of-
Stay up to date with current EAB quaran-
ways, however, and it is unlikely that EAB will
tine maps and related information at www.
ever completely disappear from an area . That
emeraldashborer.info . You can use the links
means that ash trees may always be at some
in this Web site to access specific information risk of being attacked by EAB, but it seems
for individual states . When an EAB infesta-
reasonable to expect that treatment costs
tion is detected in a state or county for the
could eventually decrease as pest pressure
first time, it will be added to these maps .
declines after the EAB wave has passed .
Note, however, that once an area has been
quarantined, EAB surveys generally stop, and
further spread of EAB in that area will not be
reflected on future maps .
4
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
Insecticide Options for
Insecticide formulations and application
control ing EAB
methods that have been evaluated for control
of EAB are listed in Table 1 . Some are mar-
Insecticides that can effectively control EAB
keted for use by homeowners while others
fall into four categories: (1) systemic insec-
are intended for use only by professional
ticides that are applied as soil injections or
applicators . The “active ingredient” refers to
drenches; (2) systemic insecticides applied
the compound in the product that is actually
as trunk injections; (3) systemic insecticides
toxic to the insect .
applied as lower trunk sprays; and (4) pro-
Formulations included in Table 1 have been
tective cover sprays that are applied to the
evaluated in multiple field trials conducted
trunk, main branches, and (depending on the by the authors . Inclusion of a product in Table
label) foliage .
1 does not imply that it is endorsed by the
Table 1. Insecticide options for professionals and homeowners for controlling EAB that
have been tested in multiple university trials . Some products may not be labeled for use in
all states . Some of the listed products failed to protect ash trees when they were applied at
labeled rates . Inclusion of a product in this table does not imply that it is endorsed by the
authors or has been consistently effective for EAB control . See text for details regarding
effectiveness .
Insecticide Formulation
Active Ingredient
Application Method
Recommended Timing
Professional Use Products
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
Inject-A-Cide B®
Bidrin®
Trunk injection
Early May to mid-June
SafariTM (20 SG)
Dinotefuran
Systemic bark spray
Early May to mid-June
Astro®
Permethrin
2 applications at 4-week intervals;
OnyxTM
Bifenthrin
first spray should occur when
Preventive bark and
black locust is blooming (early
foliage cover sprays
Tempo®
Cyfluthrin
May in southern Ohio to early
June in mid-Michigan)
Sevin® SL
Carbaryl
Homeowner Formulation
Bayer AdvancedTM Tree & Shrub
Imidacloprid
Soil drench
Mid-fall or mid- to late spring
Insect Control
Herms, McCullough, Smitley, Sadof, Williamson, Nixon
5
authors or has been consistently effective for
of imidacloprid are very similar . Homeowners
EAB control . Please see the following sec-
apply the same amount of active ingredient
tions for specific information about results
that professionals apply . However, there are
from these trials . Results of some tests have
certain restrictions on the use of homeowner
also been posted on www.emeraldashborer.
formulations that do not apply to professional
info .
formulations . Homeowner formulations of
Strategies for the most effective use of these
imidacloprid can be applied only as a drench .
insecticide products are described below . It
It is not legal to inject these products into the
is important to note that pesticide labels and
soil, although some companies have mar-
registrations change constantly and vary from keted devices to homeowners specifically for
state to state . It is the legal responsibility of
this purpose . Homeowners are also restricted
the pesticide applicator to read, understand
to making only one application per year .
and follow all current label directions for the
Several generic products containing imida-
specific pesticide product being used .
cloprid are available to homeowners, but the
formulations vary and the effectiveness of
these products has not yet been evaluated in
Using Insecticides to
university tests .
control EAB
Soil drenches offer the advantage of requir-
ing no special equipment for applica-
Soil-Applied Systemic Insecticides
tion other than a bucket or watering can .
However, imidacloprid can bind to surface
Systemic insecticides applied to the soil
layers of organic matter, such as mulch or leaf
are taken up by the roots and translocated
litter, which can reduce uptake by the tree .
throughout the tree . The most widely tested
Before applying soil drenches, it is impor-
soil-applied systemic insecticide for control of tant to remove, rake or pull away any mulch
EAB is imidacloprid, which is available under
or dead leaves so the insecticide solution is
several brand names for use by professional
poured directly on the mineral soil .
applicators and homeowners (see Table 1) .
Imidacloprid formulations labeled for use by
All imidacloprid formulations can be applied
professionals can be applied as a soil drench
as a drench by mixing the product with water, or as soil injections . Soil injections require
then pouring the solution directly on the soil
specialized equipment, but offer the advan-
around the base of the trunk . Dinotefuran
tage of placing the insecticide under mulch
was recently labeled for use against EAB as a
or turf and directly into the root zone . This
soil treatment (in addition to its use as a basal also can help to prevent runoff on sloped
trunk spray discussed below) . Studies to test
surfaces . Injections should be made just deep
its effectiveness as a soil treatment are cur-
enough to place the insecticide beneath the
rently underway in Michigan and Ohio .
soil surface (2-4 inches) . Soil injections should
Imidacloprid soil applications should be
be made within 18 inches of the trunk where
made when the soil is moist but not satu-
the density of fine roots is highest . As you
rated . Application to water-logged soil
move away from the tree, large radial roots
can result in poor uptake if the insecticide
diverge like spokes on a wheel and studies
becomes excessively diluted and can also
have shown that uptake is higher when the
result in puddles of insecticide that could
product is applied at the base of the trunk .
wash away, potentially contaminating surface
There are no studies that show that applying
waters and storm sewers . Insecticide uptake
fertilizer with imidacloprid enhances uptake
will also be limited when soil is excessively
or effectiveness of the insecticide .
dry . Irrigating the soil surrounding the base
Optimal timing for imidacloprid soil injec-
of the tree before the insecticide application
tions and drenches is mid-April to mid-May,
can improve uptake .
depending on your region . Allow four to
The application rates for the homeowner
six weeks for uptake and distribution of the
product (Bayer AdvancedTM Tree & Shrub
insecticide within the tree . In southern Ohio,
Insect Control) and professional formulations
for example, you would apply the product by
6
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
mid-April; in southern Michigan, you should
apply the product by early to mid-May .
When treating larger trees (e .g ., with trunks
larger than 12 inches in diameter), treat on
the earlier side of the recommended timing .
Large trees will require more time for uptake
and transportation of the insecticide than will
small trees . Recent tests show that imidaclo-
prid soil treatments can also be successful
when applied in the fall .
Trunk-Injected Systemic Insecticides
Several systemic insecticide products can
be injected directly into the trunk of the
tree including formulations of imidacloprid
and emamectin benzoate (see Table 1) . An
advantage of trunk injections is that they can
be used on sites where soil treatments may
not be practical or effective, including trees
growing on excessively wet, compacted or
restricted soil environments . However, trunk
Dinotefuran can be mixed with surfactants
Healthy ash trees that
injections do wound the trunk, which may
that may facilitate its movement into the tree, have been protected
cause long-term damage, especially if treat-
particularly on large trees with thick bark .
with insecticides
ments are applied annually .
However, in field trials, adding a surfactant
growing next to
did not consistently increase the amount
untreated ash trees
Products applied as trunk injections are
of insecticide recovered from the leaves of
killed by EAB.
typically absorbed and transported within
treated trees .
the tree more quickly than soil applications .
Allow three to four weeks for most trunk-
The basal trunk spray offers the advantage of
injected products to move through the tree .
being quick and easy to apply and requires
Optimal timing of trunk injections occurs
no special equipment other than a garden
after trees have leafed out in spring but
sprayer . This application technique does not
before EAB eggs have hatched, or generally
wound the tree, and when applied correctly,
between mid-May and mid-June . Uptake of
the insecticide does not enter the soil .
trunk-injected insecticides will be most effi-
cient when trees are actively transpiring . Best
Protective Cover Sprays
results are usually obtained by injecting trees
in the morning when soil is moist but not
Insecticides can be sprayed on the trunk,
saturated . Uptake will be slowed by hot after-
branches and (depending on the label)
noon temperatures and dry soil conditions .
foliage to kill adult EAB beetles as they feed
on ash leaves, and newly hatched larvae as
Noninvasive, Systemic Basal
they chew through the bark . Thorough cover-
age is essential for best results . Products
Trunk Sprays
that have been evaluated as cover sprays for
Dinotefuran is labeled for application as a
control of EAB include some specific formula-
noninvasive, systemic bark spray for EAB
tions of permethrin, bifenthrin, cyfluthrin and
control . It belongs to the same chemical class carbaryl (see Table 1) .
as imidacloprid (neonicotinoids) but is much
Protective cover sprays are designed to
more soluble . The formulated insecticide is
prevent EAB from entering the tree and will
sprayed on the lower five to six feet of the
have no effect on larvae feeding under the
trunk using a common garden sprayer and
bark . Cover sprays should be timed to occur
low pressure . Research has shown that the
when most adult beetles are feeding and
insecticide penetrates the bark and moves
beginning to lay eggs . Adult activity can
systemically throughout the rest of the tree .
be difficult to monitor because there are no
Herms, McCullough, Smitley, Sadof, Williamson, Nixon
7
effective pheromone traps for EAB . However, method were completely ineffective, even
first emergence of EAB adults generally
though tree size and infestation pressure
occurs between 450-550 degree days (start-
were very similar . It should be noted that
ing date of January 1, base temperature of
recent studies have shown that imidacloprid
50˚F), which corresponds closely with full
soil injections made at the base of the trunk
bloom of black locust (Robinia pseudoacacia) . result in more effective uptake than applica-
For best results, consider two applications,
tions made on grid or circular patterns under
one at 500 DD (as black locust approaches
the canopy .
50
full bloom) and a second spray four weeks
later .
Imidacloprid soil drenches have also gen-
erated mixed results . In some studies
conducted by MSU and OSU researchers,
how Effective Are
imidacloprid soil drenches have provided
Insecticides for control of
excellent control of EAB . However, in other
studies, control has been inconsistent . Expe-
EAB adults must feed
on foliage before they
EAB?
rience and research indicate that imidacloprid
soil drenches are most effective on smaller
become reproduc-
Extensive testing of insecticides for control
trees and control of EAB on trees with a DBH
tively mature.
of EAB has been conducted by researchers
that exceeds 15 inches is less consistent .
at Michigan State University (MSU) and The
Ohio State University (OSU) . Results of some
This inconsistency may be due to the fact
of the MSU trials are available at www .emer-
that application rates for systemic insecticides
aldashborer .info .
are based on amount of product per inch of
trunk diameter or circumference . As the DBH
Soil-Applied Systemic Insecticides
of a tree increases, the amount of vascular
tissue, leaf area and biomass that must be
Efficacy of imidacloprid soil injections for con- protected by the insecticide increases expo-
trolling EAB has been inconsistent; in some
nentially . Consequently, for a particular appli-
trials EAB control was excellent, while others
cation rate, the amount of insecticide applied
yielded poor results . Differences in applica-
as a function of tree size is proportionally
tion protocols and conditions of the trials
decreased as trunk diameter increases .
have varied considerably, making it difficult
Hence, the DBH-based application rates that
to reach firm conclusions about sources of
effectively protect relatively small trees can
variation in efficacy . For example, an MSU
be too low to effectively protect large trees .
study found that low-volume soil injections of Some systemic insecticide products address
imidacloprid applied to small trees averag-
this issue by increasing the application rate
ing 4 inches in DBH (diameter of the trunk
for large trees .
at breast height) using the Kioritz applicator
In an OSU study with larger trees (15- to
(a hand-held device for making low-volume
22-inch DBH), XytectTM (imidacloprid) soil
injections) provided good control at one
drenches provided consistent control of EAB
site . However, control was poor at another
when applied experimentally at twice the rate
site where the same application protocols
that was allowed at that time . Recently, the
were used to treat larger trees (13-inch DBH) . XytectTM label was modified to allow the use
Imidacloprid levels may have been too low in of this higher rate, which we now recommend
the larger trees to provide adequate control .
when treating trees larger than 15-inch DBH .
Higher pest pressure at the second site also
Merit® imidacloprid formulations, however,
may have contributed to poor control in the
are not labeled for application at this high
large trees .
rate . Therefore, when treating trees greater
In the same trials, high-pressure soil injections than 15-inch DBH with Merit® soil treatments,
of imidacloprid (applied in two concentric
two applications are recommended, either
rings, with one at the base of the tree and the in the fall and again in the spring, or twice
other halfway to the drip line of the canopy)
in the spring, about four weeks apart (for
provided excellent control at one site . At
example in late April and again in late May) .
another site, however, soil injections applied
This is not an option for Bayer AdvancedTM
using the same rate, timing and application
Tree and Shrub Insect Control and other
8
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
homeowner formulations of imidacloprid,
Imidacloprid • Trunk injections with imidaclo-
which are limited by the label to one applica-
prid products have provided varying degrees
tion per year . Homeowners wishing to protect of EAB control in trials conducted at different
trees larger than 15-inch DBH should con-
sites in Ohio and Michigan . In an MSU study,
sider having their trees professionally treated .
larval density in trees treated with Imicide®
Treatment programs must comply with any
injections were reduced by 60 percent to 96
limits specified on the label regarding the
percent, compared to untreated controls .
maximum amount of insecticide that can be
There was no apparent relationship between
applied per acre during a given year .
efficacy and trunk diameter or infestation
pressure . In another MSU trial, imidacloprid
Trunk-Injected Systemic Insecticides
trunk injections made in late May were more
effective than those made in mid-July, and
Emamectin benzoate • In several inten-
IMA-jet® injections provided higher levels of
sive studies conducted by MSU and OSU
control than did Imicide®, perhaps because
researchers, a single injection of emamectin
the IMA-jet® label calls for a greater amount
benzoate in mid-May or early June pro-
of active ingredient to be applied on large
vided excellent control of EAB for at least
trees . In an OSU study in Toledo, IMA-jet®
two years, even under high pest pressure .
provided excellent control of EAB on 15- to
For example, in a highly-replicated study
25-inch trees under high pest pressure when
conducted on trees ranging in size from 5-
trees were injected annually . However, trees
EAB larvae damage
to 20-inch DBH at three sites in Michigan,
that were injected every other year were not
the vascular system of
untreated trees had an average of 68 to 132
consistently protected .
the tree as they feed,
EAB larvae per m2 of bark surface, which
In a discouraging study conducted in Michi-
which interferes with
represents high pest pressure . In contrast,
gan, ash trees continued to decline from one
movement of systemic
trees treated with emamectin benzoate had,
year to the next despite being injected in
insecticides in the
on average, only 0 .2 larvae per m2, a reduc-
tree.
both years with either Bidrin (Inject-A-Cide
tion of > 99 percent . When additional trees
B®) or imidacloprid . The imidacloprid treat-
were felled and debarked two years after the
ments consisted of two consecutive years of
emamectin benzoate injection, there were
Imicide® (10% imidacloprid) applied using
still virtually no larvae in the treated trees,
Mauget® micro-injection capsules, or an
while adjacent, untreated trees at the same
experimental 12% formulation of imidaclo-
sites had hundreds of larvae .
prid in the first year followed by PointerTM
In two OSU studies conducted in Toledo
(5% imidacloprid) in the second year with
with street trees ranging in size from 15-
both applied using the WedgleTM Direct-
to 25-inch DBH, a single application of
InjectTM System . All three treatment regimes
emamectin benzoate also provided excel-
suppressed EAB infestation levels in both
lent control for two years . There was no sign
years, with Imicide® generally providing
of canopy decline in treated trees and very
best control under high pest pressure in
few emergence holes, while the canopies of
both small (six-inch DBH) and larger (16-inch
adjacent, untreated trees exhibited severe
DBH) caliper trees . However, larval density
decline and extremely high numbers of emer-
increased in treated and untreated trees from
gence holes .
one year to the next . Furthermore, canopy
dieback increased by at least 67 percent in all
One study suggests that a single injection of
treated trees (although this was substantially
emamectin benzoate may even control EAB
less than the amount of dieback observed
for three years . Additional studies to further
in untreated trees) . Even consecutive years
evaluate the long-term effectiveness of
of these treatments only slowed ash decline
emamectin benzoate are underway . To date,
under severe pest pressure . In another MSU
this is the only product that controls EAB for
study, ACECAP® trunk implants (active ingre-
more than one year with a single application .
dient is acephate) did not adequately protect
In addition, in side-by-side comparisons with
large trees (greater than 15-inch DBH) under
other systemic products (neonicotinoids),
high pest pressure .
emamectin benzoate was more effective .
Herms, McCullough, Smitley, Sadof, Williamson, Nixon
9
Protective Cover Sprays
MSU studies have shown that applications
of OnyxTM, Tempo® and Sevin® SL provided
good control of EAB, especially when the
insecticides were applied in late May and
again in early July . Acephate sprays were less
effective . BotaniGard® (Beauvaria bassiana)
was also ineffective under high pest pres-
sure . Astro® (permethrin) was not evaluated
against EAB in these tests, but has been
effective for controlling other species of
wood borers and bark beetles .
In another MSU study, spraying Tempo®
just on the foliage and upper branches or
spraying the entire tree were more effective
than simply spraying just the trunk and large
branches . This suggests that some cover
sprays may be especially effective for con-
trolling EAB adults as they feed on leaves
in the canopy . A single, well-timed spray
Noninvasive Basal Trunk Sprays with
was also found to provide good control of
Dinotefuran
EAB, although two sprays may provide extra
assurance given the long period of adult EAB
Studies to date indicate that systemic basal
activity .
trunk sprays with dinotefuran are about as
effective as imidacloprid treatments . MSU
It should be noted that spraying large trees
and OSU studies have evaluated residues
is likely to result in a considerable amount of
in leaves from trees treated with the basal
insecticide drift, even when conditions are
trunk spray . Results show that the dinotefuran ideal . Drift and potential effects of insecti-
effectively moved into the trees and was
cides on non-target organisms should be
translocated to the canopy at rates similar to
considered when selecting options for EAB
those of other trunk-injected insecticides, and control .
faster than other soil-applied neonicotinoid
products .
Acknowledgements
As with imidacloprid treatments, control of
EAB with dinotefuran has been variable in
Production and distribution of this bulletin
research trials . In an MSU study conducted
were supported in part by cooperative agree-
in 2007 and 2008, dinotefuran trunk sprays
ments from the U .S . Department of Agricul-
reduced EAB larval density by approxi-
ture’s Animal and Plant Health Inspection
mately 30 percent to 60 percent compared
Service (USDA-APHIS) and the U .S . Forest
to the heavily infested untreated trees . The
Service, Northeastern Area, Forest Health
treatment was effective for only one year
Protection . This bulletin may not necessarily
and would have to be applied annually . In
express the views of the USDA .
general, control is better and more consistent
in smaller trees than in large trees, but more
research is needed with larger trees . Studies
to address the long-term effectiveness of
annual dinotefuran applications for control of
EAB are underway .
10
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
Key Points and summary
recommendations
Insecticides can effectively protect ash trees from EAB .
Unnecessary insecticide applications waste money . If EAB has
not been detected within 10-15 miles, your trees are at low
risk . Be aware of the status of EAB in your location . Current
maps of known EAB populations can be found at www.emer-
aldashborer.info . Remember, however, that once a county is
quarantined, maps for that county are no longer updated .
Trees that are already infested and showing signs of canopy
decline when treatments are initiated may continue to decline
in the first year after treatment, and then begin to show
improvement in the second year due to time lag associated
with vascular healing . Trees exhibiting more than 50 percent
canopy decline are unlikely to recover even if treated .
Emamectin benzoate is the only product tested to date that
controls EAB for more than one year with a single application .
It also provided a higher level of control than other products
in side-by-side studies .
Soil drenches and injections are most effective when made at
the base of the trunk . Imidacloprid applications made in the
spring or the fall have been shown to be equally effective .
Soil injections should be no more than 2-4 inches deep, to
avoid placing the insecticide beneath feeder roots .
To facilitate uptake, systemic trunk and soil insecticides
should be applied when the soil is moist but not saturated or
excessively dry .
Research and experience suggest that effectiveness of insecti-
cides has been less consistent on larger trees . Research has
not been conducted on trees larger than 25-inch DBH . When
treating very large trees under high pest pressure, it may be
necessary to consider combining two treatment strategies .
XytectTM soil treatments are labeled for application at a
higher maximum rate than other imidacloprid formulations,
and we recommend that trees larger than 15-inch DBH be
treated using the highest labeled rate . Merit® imidacloprid
formulations are not labeled for use at this higher rate . When
treating larger trees with Merit® soil treatments, best results
will be obtained with two applications per year . Imidacloprid
formulations for homeowners (Bayer AdvancedTM Tree &
Shrub Insect Control and other generic formulations) can be
applied only once per year .
Homeowners wishing to protect trees larger than 15-inch
DBH should consider having their trees professionally treated .
Treatment programs must comply with any label restrictions
on the amount of insecticide that can be applied per acre in a
given year .
Herms, McCullough, Smitley, Sadof, Williamson, Nixon
11
The Cooperative Emerald Ash Borer Program
For more information and to order
additional copies of this bulletin:
www.emeraldashborer.info/
The Ohio State University EAB Outreach Team
www.ashalert.osu.edu
Purdue Extension
www.entm.purdue.edu/eab/
University of Wisconsin
www.entomology.wisc.edu/emeraldashborer/
University of Illinois
ipm .illinois .edu/landturf/insects/
University of Minnesota
www.extension.umn.edu/issues/eab/
12
InsEcTIcIdE OPTIOns fOr PrOTEcTIng Ash TrEEs frOm EmErald Ash BOrEr
June 2009
Bibliographic Citation: Herms DA, McCullough DG, Smitley DR, Sadof C, Williamson RC, and Nixon PL. 2009.
Insecticide options for protecting ash trees from emerald ash borer. North Central IPM Center Bulletin. 12 pp.
