Daniel A. Herms,
Deborah G. McCullough,
David R. Smitley,
Clifford S. Sadof,
Insecticide Options for Protecting Ash Trees from Emerald Ash Borer Daniel A. Herms1, Deborah G. McCullough2,
David R. Smitley3, Clifford S. Sadof4, Whitney Cranshaw5
1Professor, Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, 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 5Professor, Ft. Collins, CO 80523 Insecticide Options for Protecting Ash Trees from Emerald Ash Borer (Second Edition) is funded in part by the USDA-NIFA North Central Integrated Pest Management Center (Funding Award: 2011-51120-31160).
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 have shown that even large ash
Fairmaire), an invasive insect native trees can be effectively and con- to Asia, has killed untold millions of sistently protected over multiple ash trees (Fraxinus species) in urban, rural years, even in areas with high and forested settings. This beetle was first densities of EAB. Recent economic identified in 2002 in southeast Michigan and analyses have concluded that Windsor, Ontario. As of April 2014, emerald treating landscape ash trees with ash borer (EAB) infestations were known effective systemic insecticides is to be present in 22 states as well as two much less costly than removing Canadian provinces. Surveys continue and additional infestations will be found as EAB Our understanding of how EAB continues to invade North America. Ash trees can be managed successfully with are common in urban landscapes and resi- insecticides has advanced since dential areas across much of the continental this bulletin was initially published US. Many homeowners, tree care profession- in 2009. This version has been revised to als, and municipalities would like to protect address frequently asked questions and valuable ash trees from EAB. reflect the current state of understanding of Since 2002, our ability to control EAB and insecticide options for controlling EAB and effectively protect ash in the landscape has their effectiveness. It is important to note that progressed substantially. Scientists have research is an ongoing process. Scientists learned much about this insect and how it from universities, government agencies and interacts with its host trees. New insecticide companies will continue to make discover- products and application methods have been ies and advance EAB management and ash developed and tested. Results of field trials Herms, McCullough, Smitley, Sadof, Cranshaw
Answers to Frequently thin because fewer leaves can be supported by the tree. Large branches or even the trunk can be girdled and killed by the larval galleries. What options do I have for treating my
ash trees?
Multi-year studies have shown that if more than 50% of the canopy has been killed by Several insecticide options are available to EAB or if the canopy appears to be thin and effectively treat landscape ash trees threat- carrying less than half as much foliage as it ened by EAB. Products listed in Table 1 have should, it is probably too late to save the been evaluated by university and govern- tree. The ability of trees to recover from low ment scientists in field trials. Keep in mind, to moderate EAB injury can vary, depend- however, that controlling insects that feed ing on the extent of the damage and which under the bark with insecticides has always control options are used. Studies have also been challenging. This is especially true with shown that if the canopy of a tree is already EAB because most of our native North Ameri- declining when insecticide treatments are can ash trees have little natural resistance to initiated, the condition of the tree may this pest. Effective control of EAB requires continue to deteriorate during the first year some care when selecting an insecticide of treatment. If treatment is effective, the product and application method to ensure tree canopy will usually begin to improve in the product is applied at the proper rate and the second year of treatment. This lag in the reversal of canopy decline probably reflects the time needed for the tree to repair its I know my tree is already infested with vascular system after the EAB infestation has
EAB. Will insecticides still be effective? been reduced.
It is best to begin using insecticides while
ash trees are still relatively healthy. By the
My ash tree looks fine but EAB has
time most people notice canopy thinning or been detected in the vicinity of my
dieback, EAB has already caused consider- property. Should I start treating my
ably injury to the vascular system of the tree. An effective insecticide may stop additional Detecting new EAB infestations and identify- damage, but it cannot reverse damage that ing ash trees that have only a few larvae is has already occurred and it takes time for very difficult. Ash trees with low densities of trees to recover. Most insecticides used for EAB larvae often have few or even no exter- EAB control act systemically - the insecti- nal symptoms of infestation. In addition, cide must be transported within the tree. In scientists have learned that most female EAB other words, a tree must be healthy enough lay their eggs on nearby trees, i.e. within 100 to carry a systemic insecticide up the trunk yards of the tree from which they emerged. and into the branches and canopy. Trees are A few female beetles, however, appear to damaged by EAB larvae feeding in galler- disperse much further, anywhere from 0.5 ies under the bark. These galleries injure the miles to 2-3 miles. Therefore, if your property phloem and xylem tissue that plants use to is within 10-15 miles of a known EAB infes- transport nutrients and water. A few galleries tation, your ash trees are probably at risk. have only a small effect on most trees. As the If your ash trees are more than 10-15 miles EAB population grows and more larvae feed beyond an infestation, it is probably too early on a tree, however, the galleries interfere with to begin insecticide treatments. Treatment the ability of the tree to transport nutrients programs that begin too early waste money and water, as well as insecticides. As a tree and result in unnecessary use of insecticide. becomes more and more infested, the injury Conversely, treatment programs that begin becomes more severe. Canopies become too late will not be as effective.
INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER Remember, however, that new EAB infesta-tions have been discovered every year since 2002 and existing EAB populations will build and spread over time. Quarantine maps website can help you stay up-to-date regard-ing locations of known infestations. You can use the links in this website to access spe-cific information for individual states. When an EAB infestation is detected in a state or county for the first time, it will be added to these quarantine maps. Note, however, that once EAB has been found in a county, surveys by regulatory officials end. Similarly, once an entire state is declared to be infested, regulatory surveys may cease. Therefore, quarantine maps may or may not adequately reflect the current dis-tribution of EAB in such areas. Personnel from city, county or state agencies sometimes con-tinue to survey or monitor local EAB infesta-tions. City foresters, county extension offices or state departments of agriculture may have information on local EAB distribution. There is no substitute for local knowledge and tree care professionals should actively monitor changes in the condition of local ash trees.
When is the best time to treat my
As with any pest management effort, optimal timing is required to achieve best control. Two life stages of EAB are targeted by laying eggs. This provides a window of Ash trees on a street
treatments: adult beetles and young larvae. opportunity to control the adults before any in Toledo in 2006 and
Therefore, systemic insecticide applications new eggs or larvae are produced. The onset 2009 before and after
should be made in time to allow for uptake being impacted by
of adult beetle emergence begins from early and distribution of the insecticide within the May (southern Ohio) to early June (central tree to ensure adult beetles and very young Michigan) and peaks two to three weeks larvae encounter the toxin. Non-systemic later. Beetle emergence may begin sooner at cover sprays, which are less commonly used, locales farther south or later in more northern should be applied to foliage to target adult areas. Regardless of location, emergence beetles, as well as the trunk and branches to of adult EAB consistently begins at 450-550 help control newly hatched larvae. Thorough growing degree days, based on a threshold coverage is critical for achieving successful of 50 ºF and a starting date of January 1. Beetles are most abundant at about 1,000 Adult EAB feed on ash foliage throughout growing degree days. Cumulative growing their life span and females must feed on degree days are tracked and posted on leaves for at least 14 days before they begin websites of many land grant universities as well as the NOAA website. First emergence Herms, McCullough, Smitley, Sadof, Cranshaw
of EAB also closely coincides with the period that imidacloprid trunk injections made in when black locust trees bloom. This pheno- mid-May were 70% more effective against logical indicator is a reliable predictor of EAB EAB than those made in mid-July. emergence across a wide region, ranging For imidacloprid soil treatments, which from southern Michigan to Kentucky and require four to six weeks for uptake and distribution of the insecticide within the tree, Peak egg hatch and larval establishment applications should be made in mid-March occur between early June and mid-August, to late April, depending on your region. depending on location and weather. As a Treatments should be applied on the earlier general rule, young larvae are more suscep- side of these schedules in more southerly tible to insecticides than are older larvae. locations and later side in more northerly Moreover, controlling young larvae pre- regions. Soil applications of dinotefuran can vents damage to the tree caused by older be applied 2-3 weeks later than imidaclo- larvae that feed in larger galleries and thus prid because it is more soluble and is taken injure more area on the tree. The efficacy of up and transported through the tree more insecticide treatments will likely decline if rapidly. Basal trunk sprays of dinotefuran they are applied later in the growing season move into trees even faster and can be made when larger, more mature larvae are present. between late May and mid-June. Optimal Consistent with this, MSU scientists found timing for trunk injected products is just after trees have leafed out, typically from mid-May through early or mid-June. When How can I convince my community that action must be
treating larger trees, treat on the earlier side taken before it is too late to save the ash trees?
of the recommended timing, because large The first step is to educate your community about the threat trees may require more time for uptake and posed by EAB and the value of the ash trees in the community. transportation of the insecticide than small Members of some communities have acquired permission to trees. Imidacloprid soil applications can mark ash trees with visual tags. This allows residents to clearly also be made in fall, from mid-October to see the extent of the resource at risk. Other suggestions for mid-November. However, this timing is less organizing communities can be found in the "Neighbors Against efficient and studies have shown that higher Bad Bugs" website. You will want to cooperate with your city rates must be applied in the fall than in forester who may already have an inventory of street trees. An spring to achieve similar levels of control.
inventory will help identify where the ash trees are located, the Sometimes, a tree is not known to be size and species of the ash trees, and the proportion of the infested until in late June or early July. public forest at risk. Some cities use sophisticated inventory Although late treatments are not optimal, systems that even calculate the value of the services provided there may still be some benefit to treating the by the ash trees. In Milwaukee, WI, for example, the capacity of tree if the treatment can be made promptly. ash trees to filter storm water saves the city more than enough Consider using a treatment approach that money to justify the cost of treating the trees. Other cities use maximizes rate of uptake and within-tree dis- similar programs to create visible tree tags that tally the dollar tribution. Uptake of dinotefuran is faster than value of the services provided by each tree. The National Tree imidacloprid because it is more soluble. Basal Benefits Calculator website provides information on calculating trunk sprays with dinotefuran will be taken the value of trees for professional arborists and urban forest- up faster than soil applications (see discus- ers. You may also wish to estimate or compare costs of different sion below). Trunk injections will be taken up management responses to the EAB invasion over time. The EAB faster than soil applications, assuming the Cost Calculator website at Purdue University, for example, allows injections can be made under favorable con- users to enter their own tree inventory, compare local costs of ditions (e.g. adequate soil moisture, moder- treatment options or tree removal, and print reports. Links to ate humidity and air temperature). Even in a these websites ar best case scenario, it will still likely take one using the website name in a google search. to two weeks for the systemic insecticide to move throughout the tree.
ash trees from EAB for several years. Is
My customers want to know about the environmental
it worth it?
effects of systemic insecticides used to protect ash
trees from EAB.
The economics of treating ash trees with insecticides for EAB protection are com- People often have questions about whether systemic insecticide plicated and depend on several factors. products used to protect ash trees will harm the environment Tree size, health, location and value should or other organisms such as woodpeckers. A bulletin entitled be considered, along with the cost of the "Frequently Asked Questions Regarding Potential Side Effects insecticide and expense of application, the of Systemic Insecticides Used to Control Emerald Ash Borer" likelihood of success, and potential costs of removing the trees. Scientists, however, page bulletin can be viewed on the website or downloaded and have compared costs of removing urban printed for distribution. ash trees versus treating the same trees with emamectin benzoate, which provides two years of EAB control. Results consistently for example, indicate EAB populations still show treatment costs are much lower than persist but at much lower densities simply removal costs. As treatment options con- because few mature ash trees remain in this tinue to evolve, costs of treatment will likely area. Young ash saplings in forests or wood- change. It will be important to stay up to lots will likely be colonized by EAB eventu- date on these options and management ally, so landscape ash may continue to face recommendations. some risk of EAB infestation. It seems likely, however, that surviving ash trees can be Benefits of treating trees can be more difficult managed with less frequent treatments once to quantify than costs. Healthy landscape the EAB invasion has passed. Studies on the trees typically increase property values, dynamics of EAB populations and whether provide shade and cooling, and contribute to the intensity of insecticide treatments can the quality of life in a neighborhood. Land- decrease after the local EAB population has scape trees, especially mature trees, capture collapsed are underway in Michigan and storm water, reducing potential pollution of streams and rivers. The economic benefits provided by trees increase with the size of the tree, as does the cost of removal. Hence, Insecticide Options for it may be particularly economical to treat larger trees. Many people are sentimental about their trees. These intangible quali- Insecticides that can effectively control EAB ties are important and should be part of any fall into four categories: (1) systemic insec- decision to invest in an EAB management ticides that are applied as soil injections or drenches; (2) systemic insecticides applied as trunk injections; (3) systemic insecticides It is also worth noting that the size of EAB applied as lower trunk sprays; and (4) pro- populations in a specific area will change tective cover sprays that are applied to the over time. Populations initially build very trunk, main branches, and (depending on the slowly, but later increase rapidly as more trees become infested. As EAB populations reach peak densities, a high proportion of Insecticide formulations and application the untreated ash trees in a given area will methods that have been evaluated for control decline and die, usually over a 3-5 year of EAB are listed in Table 1. Some are mar- period. Once untreated ash trees in the area keted for use by homeowners while others succumb, however, the local EAB population are intended for use only by professional will decrease substantially. Ongoing studies applicators. The "active ingredient" refers to in southeast Michigan and northwest Ohio, the compound in the product that is actually toxic to the insect. Herms, McCullough, Smitley, Sadof, Cranshaw
Formulations included in Table 1 have been injections require specialized equipment, evaluated in multiple field trials conducted by but offer the advantage of placing the the authors and other university and govern- insecticide below mulch or turf and directly ments researchers. Inclusion of a product in into the root zone of the tree. This also can Table 1 does not imply that it is endorsed by help to prevent runoff on slopes. Injections the authors or has been consistently effec- should be made just deep enough to place tive for EAB control. Please see the following the insecticide beneath the soil surface (2-4 sections for specific information about results inches). Soil injections should be made within from these trials. 18 inches of the trunk. Studies have shown Strategies for the most effective use of these uptake is higher and the treatment more insecticide products are described below. It effective when the product is applied at the is important to note that pesticide labels and base of the trunk where the density of fine registrations change constantly and vary from roots is highest. As you move away from the state to state. It is the legal responsibility of tree, large radial roots diverge like spokes on the pesticide applicator to read, understand a wheel and fine root density decreases. Soil and follow all current label directions for the drenches offer the advantage of requiring no specific pesticide product being used. special equipment for application other than a bucket or watering can. However, imida-cloprid can bind to surface layers of organic Using Insecticides to matter, such as mulch or leaf litter, which can reduce uptake by the tree. Before applying soil drenches, it is important to remove, rake Soil-Applied Systemic Insecticides
or pull away any mulch or dead leaves so the insecticide solution is poured directly on the Imidacloprid and dinotefuran are systemic insecticides that can be applied as soil Rates of soil applied insecticides needed to drenches or soil injections. Both are sold provide effective control may vary depend- under numerous brand names for use by ing on the size of the tree and the intensity professional applicators and homeowners. of pest pressure at the site. Higher rates of Those that have been tested by the authors some imidacloprid products available to pro- are listed in Table 1; other similar products fessionals and homeowners can be applied are also available. Soil applications can to large trees with trunk diameters greater applied as a drench by mixing the product than 15 inches. Lower rates are effective on with water, then pouring the solution directly smaller trees and when EAB populations on the soil around the base of the trunk, or and pest pressure are relatively low. When injected a few inches below ground at mul- treating larger trees with imidacloprid or tiple locations near the base of the tree. The dinotefuran soil treatments, particularly when insecticide is taken up by the roots of the tree EAB density is high, studies have shown that and then moves (translocates) throughout the applying the highest labeled rate is most effective. Only some imidacloprid products Products designed for homeowners have can be applied at the higher rate and only some restrictions that do not apply to profes- if trees are greater than 15 inches in diam- sional formulations. Homeowner products eter, so please review the label closely when can be applied as a soil drench or as granules selecting a product. that are watered into the soil, but not as a soil Treatment programs must also comply with injection. Homeowners are also restricted to the limits specified on the label regarding making only one application per year. the maximum amount of insecticide that Professionals can apply these products as can be applied per acre during a given year. a soil injection as well as a soil drench. Soil INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER 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. 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. Additional imidacloprid products may be
available in your area. See text for details regarding effectiveness.
Products Intended for Sale to Professional Applicators Merit® (75WP, 75WSP, 2F) Soil injection or drench Early to mid-spring or mid-fall Safari TM (20 SG) Soil injection or drench Mid- to late spring Transect TM (70WSP) Soil injection or drench Mid- to late spring XytectTM (2F, 75WSP) Soil injection or drench Early to mid-spring or mid-fall Zylam® Liquid Systemic Insecticide Soil injection or drench Mid- to late spring Mid- to late spring after trees Mid- to late spring after trees Mid- to late spring after trees Emamectin benzoate Mid- to late spring after trees Mid- to late spring after trees Systemic bark spray Transect (70 WSP) Mid- to late spring after trees Systemic bark spray Mid- to late spring after trees Zylam® Liquid Systemic Insecticide Systemic bark spray Two applications at 4-week intervals; first spray should occur Preventive trunk, branch, at 450-550 degree days (50ºF, and foliage cover sprays Jan.1); coincides with black locust blooming Products Intended for Sale to Homeowners Bayer AdvancedTM Tree & Shrub Early to mid-spring Early to mid-spring Ortho Tree and Shrub Insect Control Ready to Use Granules® Mid- to late spring Herms, McCullough, Smitley, Sadof, Cranshaw
This restricts the number of trees that can be emamectin benzoate (TREE-age™) injected treated in an area. with Arborjet equipment and imidacloprid Soil applications should be made when the (Imicide®)) injected with Mauget capsules soil is moist but not saturated. Insecticide in May, however, showed ash trees rapidly uptake will also be limited when soil is exces- recovered and began producing new wood sively dry. You may need to irrigate the soil over the wounds in late summer. Application surrounding the base of the tree before and methods that rely on high pressure injections possibly after the insecticide application if of insecticide through needles inserted into soils are dry. However, water-logged soil small holes may damage the tree if the pres- can result in poor uptake if the insecticide sure causes the bark to bulge and separate becomes excessively diluted and can also from the cambium. This is most likely to occur result in puddles of insecticide that could in spring and can cause larger wounds that wash away, potentially entering surface water result from death of the vascular tissue at the EAB adults must feed
or storm sewers. To further protect surface point of separation. on foliage before they
and ground water, soil applications should Products applied as trunk injections are not be made to excessively sandy soils with typically absorbed and transported within low levels of organic matter that are prone to the tree more quickly than soil applications. leaching, especially where the water table is Allow at least two and preferably three to shallow, or where there is risk of contaminat- four weeks for most trunk-injected products ing gutters, lakes, ponds, or other bodies of to move through the tree. Optimal timing of trunk injections occurs after trees have leafed No soil applications should be made where out in spring but before EAB eggs have there are roots of flowering plants that are hatched, or generally between mid-May and visited by bees and other pollinators. This mid-June. Uptake of trunk-injected insecti- situation is most likely to occur where flower- cides will be most efficient when trees are ing plants are established around the base of actively transpiring. Best results are usually an ash tree. In these situations the flowering obtained by injecting trees in the morning plants should either be destroyed or insecti- when soil is moist but not saturated. Uptake cide should be applied via trunk injection to will be slowed by hot afternoon temperatures ensure the toxins will not be taken up by the and dry soil conditions. Irrigating trees during flowering plants. droughty conditions will help with insecticide uptake and translocation within the tree. Trunk-Injected Systemic Insecticides
Noninvasive, Systemic Basal Trunk
Several systemic insecticide products can be injected directly into the trunk of the tree including formulations of azadirachtin, Dinotefuran is labeled for application as a emamectin benzoate, and imidacloprid (see noninvasive, systemic trunk spray for EAB Table 1). An advantage of trunk injections control. It belongs to the same chemical class is that they can be used on sites where soil as imidacloprid (neonicotinoids) but is much treatments may not be practical, effective more water soluble and moves more readily or appropriate, including trees growing through plants. The formulated insecticide on excessively wet, sandy, compacted or is sprayed on the lower five to six feet of the restricted soil environments. Trunk injec- trunk using a common garden sprayer and tions generally involve drilling through the low pressure. Research has shown that the bark and into the outer sapwood at the base insecticide penetrates the bark and is trans- of the tree. Drilling wounds could cause ported systemically throughout the tree. long-term damage, especially if treatments The basal trunk spray offers the advantage of are applied annually. Recent studies of being quick and easy to apply and requires INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER no special equipment other than a garden sprayer. This application technique does not wound the tree, and when applied correctly, the insecticide does not enter the soil. Spray-ers must be calibrated to ensure the appro-priate amount of the formulated product is applied to each tree. Dinotefuran can be mixed with surfactants that may facilitate its movement into the tree, particularly on large trees with thick bark. However, in field trials, adding a surfactant did not consistently increase the amount of insecticide recovered from the leaves of treated trees or improve the effectiveness of the application.
Protective Cover Sprays
Insecticides can be sprayed on the trunk, branches and (depending on the label) foliage to kill adult EAB beetles as they feed on ash leaves, and newly hatched larvae as they chew through the bark. Thorough cover-age is essential for best results. Products that have been evaluated as cover sprays for control of EAB include some specific formula-tions of permethrin, bifenthrin, cyfluthrin and carbaryl (see Table 1). Protective cover sprays are designed to control EAB adults and perhaps very young larvae that have just hatched from eggs. Sprays will have no effect on larvae feeding under the bark. Cover sprays should be timed to occur when most adult beetles have emerged and are feeding on ash leaves. For best results, consider two applications, one at 500 DD (as black locust approaches full bloom) and a second spray four weeks later. Keep in mind that maintaining good growing Healthy ash trees that
conditions and avoiding major stresses will have been protected
How Effective Are improve your chances of successfully protect- with imidacloprid
soil drenches in 2009

Insecticides for Control ing your trees.  Be sure to water trees during growing next to
extended dry periods.  untreated ash trees
injured by EAB. The

Soil-Applied Systemic Insecticides
same street in 2011
Extensive testing of insecticides for control following six con-
of EAB has been conducted by researchers Efficacy of soil-applied systemic insecticides secutive years of
at Michigan State University (MSU) and The for controlling EAB has been inconsistent. In treatments during a
Ohio State University (OSU). The following some OSU and MSU trials, EAB control was peak EAB outbreak.
sections summarize key results of these trials. excellent, while others yielded poor results. Untreated trees
declined and were

Herms, McCullough, Smitley, Sadof, Cranshaw
Application protocols and conditions of the Trunk-Injected Systemic Insecticides
trials have varied considerably, making it dif- Emamectin benzoate • In several inten-
ficult to reach firm conclusions about sources sive studies conducted by MSU and OSU of variation in efficacy. This inconsistency may researchers, a single injection of emamectin reflect the fact that application rates for soil- benzoate (TREE-äge™) in mid-May or early applied systemic insecticides are based on June provided excellent control of EAB for amount of product per inch of trunk diameter at least two years, even when EAB densities or circumference. As the trunk diameter of a were high. For example, in a highly-replicated tree increases, the amount of vascular tissue, study conducted on trees ranging in size from leaf area and biomass that must be protected 5 to 21-inch DBH at three sites in Michigan, by the insecticide increases exponentially. untreated trees had an average of 68 to 132 Consequently, for a particular application EAB larvae per m2 of bark surface, which rep- rate, the amount of insecticide applied resents high pest pressure. In contrast, trees as a function of tree size is proportionally treated with low rates of emamectin benzo- decreased as trunk diameter increases. ate (0.1-0.2 g ai / inch DBH) had, on average, Hence, application rates based on diameter only 0.2 larvae per m2, a reduction of >99 at breast height (DBH) may effectively protect percent. When additional trees were felled relatively small trees but can be too low to and debarked two years after the emamectin EAB larvae damage
effectively protect large trees. Some systemic benzoate injection, there were still virtually the vascular system of
insecticide products address this issue by the tree as they feed,
no larvae in the treated trees, while adjacent, increasing the application rate for large trees. which interferes with
untreated trees at the same sites had hun- movement of systemic Some imidacloprid formulations can be
dreds of larvae. insecticides in the
applied to trees with a trunk diameter greater In two Ohio studies with street trees ranging than 15 inches at a rate that is twice as high in size from 15- to 25-inch DBH, a single (2X rate) as the rate used for smaller trees (1X application of emamectin benzoate provided rate). In an OSU study in Toledo, Ohio under- excellent control for two years, even at the way since 2006, imidacloprid soil drenches lowest rate. There was no sign of canopy have effectively protected ash trees ranging decline in treated trees and very few emer- from 15-22 inches in diameter when applied gence holes, while the canopies of adjacent, at the 1X rate in spring, or at the 2X rate untreated trees exhibited severe decline and when applied in spring or fall. These treat- extremely high numbers of emergence holes. ments were effective even during years of In another trial, large trees, ranging from 32 peak pest pressure when all of the untreated to 47 inches DBH, were treated in alternate trees died. Trees treated in fall with the 1X years with emamectin benzoate at medium- rate, however, declined and were removed. In low or medium-high rates. Canopies of all another OSU multi-year trial with trees up to treated trees remained healthy four years 22 inches DBH, dintotefuran soil applications, later (after two treatments) despite high pest as well as basal trunk sprays (see below) were pressure and numerous declining (untreated) effective when applied at the highest labeled trees in the immediate vicinity. rate. However, lower rates were less effective. We are not aware of any studies that evalu- Additional studies have been conducted ated soil applied insecticides with trees larger since then in other sites and all have pro-than 22 inches DBH. duced similar results. Injections of emamectin benzoate, even at the lowest rate on the Insecticide placement may also affect effi- label (0.1 ga ai/DBH inch), provide nearly cacy. Recent studies have shown that soil complete EAB control for two years. Depend- drenches and injections made at the base of ing on application rate and pest pressure, the trunk result in more effective uptake than treatment with emamectin benzoate may applications made on grid or circular patterns under the canopy away from the trunk. INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER even protect trees for three years. Moreover, in side-by-side comparisons, emamectin ben-zoate was more effective than other systemic neonicotinoid products. Azadirachtin • Results from a two-year study
in Michigan replicated at three sites showed
azadirachtin products affect EAB differently
than other insecticide products. For example,
adult EAB beetles fed for six days on leaves
from trees treated with a high rate of azadi-
rachtin (TreeAzin®), then fed on leaves from
untreated trees for the remainder of their
life span. In contrast to trees treated with
either emamectin benzoate (trunk injection)
or dinotefuran (basal trunk spray), leaves
from the azadirachtin trees were not acutely
toxic to adult beetles. However, azadi-
rachtin reduced the ability of mature female
beetles to produce viable eggs that success-
fully hatched. Young females, conversely,
appeared to recover and were able to repro-
duce normally.
When the trees in this study were felled and debarked after two years of exposure to EAB, it was apparent that numerous EAB larvae had begun feeding on trees treated with TreeAzin but died while still young and small. Very few live larvae were present on the trees treated in both years with TreeAzin. When trees were treated only the first year trunk injections made in late May were more Healthy ash trees
protected with ema-

but not the second year, density of live larvae effective than those made in mid-July, and mectin benzoate trunk
was 75-80% lower than on untreated control IMA-jet® injections provided higher levels of injections behind an
trees. Results from this study suggest that in control than did Imicide®, perhaps because untreated, declining
most years, TreeAzin will effectively protect the IMA-jet® label calls for a greater amount ash trees for two years, but when EAB densi- of active ingredient to be applied on large ties are high, annual applications may be trees. In an OSU study in Toledo, IMA-jet® provided excellent control of EAB on 15- to 25-inch trees under high pest pressure when trees were injected annually. However, trees Imidacloprid • Trunk injections with imidaclo-
that were injected every other year were not prid products have provided varying degrees of EAB control in trials conducted at different In a discouraging study conducted in Michi- sites in Ohio and Michigan. In an MSU study, gan, ash trees continued to decline from one larval density in trees treated with Imicide® year to the next despite being injected in injections were reduced by 60 percent to 96 both years with either Bidrin (Inject-A-Cide percent, compared to untreated controls. B®) or imidacloprid. The imidacloprid treat- There was no apparent relationship between ments consisted of two consecutive years of efficacy and trunk diameter or infestation Imicide® (10% imidacloprid) applied using pressure. In another MSU trial, imidacloprid Mauget® micro-injection capsules, or an Herms, McCullough, Smitley, Sadof, Cranshaw
experimental 12% formulation of imidaclo- research trials. In an MSU study conducted prid in the first year followed by PointerTM in 2007 and 2008, annual dinotefuran trunk (5% imidacloprid) in the second year with sprays reduced EAB larval density by approxi- both applied using the WedgleTM Direct- mately 30 to 60 percent compared to the InjectTM System. All three treatment regimens heavily infested untreated trees. As with suppressed EAB infestation levels in both dinotefuran and imidacloprid soil applica- years, with Imicide® generally providing tions, the basal trunk treatment was effec- best control under high pest pressure in tive for only one year and would have to be both small (six-inch DBH) and larger (16-inch applied annually. DBH) caliper trees. However, larval density In a five-year OSU study with trees up to 22 increased in treated and untreated trees from inches DBH, dinotefuran basal bark sprays one year to the next. Furthermore, canopy provided effective protection when applied at dieback increased by at least 67 percent in all the highest labeled rate (average of less than treated trees (although this was substantially 5% canopy decline compared with nearly less than the amount of dieback observed 80% average canopy decline for untreated in untreated trees). Even consecutive years trees). A lower rate was not as effective of these treatments only slowed ash decline (almost 20% average canopy decline). under severe pest pressure. In a head-to-head comparison of products Protective Cover Sprays
conducted by OSU researchers, emamectin MSU studies have shown that applications benzoate trunk injections (0.4 g a.i. / inch of OnyxTM, Tempo® and Sevin® SL provided DBH applied during the first year in May) and good control of EAB, especially when the imidacloprid soil drenches (applied in both insecticides were applied in late May and years in May at the highest labeled rates) again in early July. Acephate sprays were less provided effective control of EAB. In con- effective. BotaniGard® (Beauvaria bassiana) trast, trees treated with PointerTM (5% imida- was also ineffective under high pest pres- cloprid applied in both years in May at the sure. Astro® (permethrin) was not evaluated highest labeled rate) and the untreated trees against EAB in these tests, but has been declined substantially over the two year study effective for controlling other species of period. In another MSU study, ACECAP® wood borers and bark beetles.
trunk implants (active ingredient is acephate) did not adequately protect trees > 15-inch In another MSU study, spraying Tempo® DBH under high pest pressure.
just on the foliage and upper branches or spraying the entire tree were more effective Noninvasive Systemic Basal
than simply spraying just the trunk and large Trunk Sprays
branches. This suggests that some cover sprays may be especially effective for con- Studies to date indicate that the effectiveness trolling EAB adults as they feed on leaves of dinotefuran basal trunk sprays are similar in the canopy. A single, well-timed spray to soil applications of dinotefuran or imida- was also found to provide good control of cloprid. MSU and OSU studies have evalu- EAB, although two sprays may provide extra ated residues in leaves from trees treated assurance given the long period of adult EAB with the basal trunk spray. Results show that the dinotefuran effectively moved into the trees and was translocated to the canopy at It should be noted that spraying large trees rates similar to those of other trunk-injected is likely to result in a considerable amount of insecticides, and faster than other soil- insecticide drift, even when conditions are applied neonicotinoid products. ideal. Drift and potential effects of insecti-cides on non-target organisms should be As with imidacloprid treatments, control of considered when selecting options for EAB EAB with dinotefuran has been variable in INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER Key Points and Summary Recommendation Insecticides can effectively and consistently protect Trunk injections of azadirachtin affect EAB differ- even very large ash trees from EAB, even under ently than other systemic insecticides. Results from intense pest pressure.
a recent study indicate azadirachtin should provide Drought stress inhibits uptake and transport of effective protection for one to two years, depending systemic insecticides. Supplemental irrigation will be on EAB pressure.
needed during dry periods.
Basal trunk sprays with dinotefuran applied annu- Unnecessary insecticide applications waste money. ally effectively protected ash trees up to 22 inches However, EAB infestations are very difficult to detect DBH in several studies. It is important to calibrate when populations are low. Once EAB has been sprayers to ensure the proper rate of the formulated detected within 10-15 miles, your trees may be at product is applied. risk. Be aware of the status of EAB in your location. Imidacloprid and dinotefuran soil applications pro- Current maps of counties and states where EAB has vided effective EAB control of trees up to 22 inches DBH (larger trees were not tested) when applied , however, that once a county is annually at the highest labeled rate, even under quarantined, regulatory surveys end and maps for intense pest pressure. Soil drenches and injections that county are no longer updated. In some areas, are most effective when the product is applied at local information on EAB infestations may be avail- the base of the trunk. Generally, imidacloprid soil able from city, county or state officials.
applications are more effective when applied in the Trees exhibiting more than 50 percent canopy spring than in the fall. Soil injections should be no decline (thinning or dieback) are unlikely to recover more than 2-4 inches deep, to avoid placing the even if treated with a highly effective systemic insec- insecticide beneath feeder roots of the tree. To ticide. Trees that are already infested and showing facilitate uptake, systemic trunk and soil insecticides signs of canopy decline when treatments are initi- should be applied when the soil is moist but not ated may continue to decline the first year after saturated or excessively dry.
treatment, and then begin to improve the second When treating trees greater than 15 inches DBH year, as the trees recover. Effectiveness of products with imidacloprid soil applications, select a product varies and depending on the product applied and that allows a higher rate (2X rate) to be used. Not all the pest pressure, trees with lower levels of canopy imidacloprid products can be applied at that rate, decline may not recover despite treatment.
so check the label carefully. Users must comply with Emamectin benzoate consistently provides at least all restrictions on the frequency of applications and two years of EAB control with a single application, the amount of insecticide that can be applied per even in large and very large trees under intense pest acre in a given year. pressure. It also provided a higher level of control than other products in side-by-side studies.
Herms, McCullough, Smitley, Sadof, Cranshaw
The Cooperative Emerald Ash Borer Program
For more information and to download additional copies of this bulletin: The Ohio State University EAB Outreach Team
Bibliographic Citation: Herms DA, McCullough DG, Smitley DR, Clifford CS, Cranshaw W. 2014. Insecticide options for protecting ash trees from emerald ash borer. North Central IPM Center Bul etin. 2nd Edition. 16 pp.

Source: http://www.emeraldashborer.info/documents/Multistate_EAB_Insecticide_Fact_Sheet.pdf



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