Emerald Ash Borer Research Articles

Guidelines for statistically sound and risk‐based surveys of Agrilus planipennis

Guidelines for statistically sound and risk‐based surveys of Agrilus planipennis

Optimal planning of multi‐day invasive species surveillance campaigns

Abstract Multi‐day survey campaigns are critical for timely detection of biological invasions. We propose a new modelling approach that helps allocate survey inspections in a multi‐day campaign aimed at detecting the presence of an invasive organism. We adopt a team orienteering problem to plan daily inspections and use an acceptance sampling approach to find an optimal surveillance strategy for emerald ash borer in Winnipeg, Manitoba, Canada. The manager's problem is to select daily routes and determine the optimal number of host trees to inspect with a particular inspection method in each survey location, subject to upper bounds on the survey budget, daily inspection time, and total survey time span. We compare optimal survey strategies computed with two different management objectives. The first problem minimizes the expected number of survey sites (or area) with undetected infestations. The second problem minimizes slippage – the expected number of undetected infested trees in sites that were not surveyed or where the surveys did not find infestation. We also explore the impact of uncertainty about site infestation rates and detection probabilities on the surveillance strategy. Accounting for uncertainty helps address temporal and spatial variation in infestation rates and yields a more robust surveillance strategy. The approach is generalizable and can support delimiting survey programs for biological invasions at various spatial scales.

Diversity of secoiridoid glycosides in leaves of UK and Danish ash provide new insight for ash dieback management

Secoiridoid glycosides are anti-feeding deterrents of the Oleaceae family recently highlighted as potential biomarkers in Danish ash trees to differentiate between those tolerant and susceptible to the fungal disease ash dieback. With the knowledge that emerald ash borer has recently entered Europe from Russia, and that extensive selection trials are ongoing in Europe for ash dieback tolerant European ash (Fraxinus excelsior), we undertook comprehensive screening of secoiridoid glycosides in leaf extracts of trees tolerant and susceptible to ash dieback sampled from sites in the UK and Denmark. Here we report an unexpected diversity of secoiridoid glycosides in UK trees and higher levels of secoiridoid glycosides in the UK sample group. While it is unlikely that secoiridoid glycosides generally can serve as reliable markers for ash dieback susceptibility, there are differences between tolerant and susceptible groups for specific secoiridoids. We predict that the high levels—and structural diversity—of secoiridoids present in the UK group may provide a robust reservoir of anti-feeding deterrents to mitigate future herbivore threats such as the Emerald ash borer.

Effects of Low Temperature Exposure on Diapause, Development, and Reproductive Fitness of the Emerald Ash Borer (Coleoptera: Buprestidae): Implications for Voltinism and Laboratory Rearing.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), native to Northeast Asia, is the most destructive invasive ash (Fraxinus spp.) pest in the United States. In the present study, we evaluated the effect of exposure of diapausing mature fourth instars (J-shaped larvae, JL) of EAB to cool temperatures, either 1.7 or 12.8°C for 1-9 mo, on their post-chill development including adult emergence, longevity, and lifetime fecundity under standard rearing conditions (26 ± 0.5°C, 16:8 h L:D). In addition, we determined the effect of different stages of the larvae chilled at 12.8°C for 3 mo on the subsequent post-chill development to EAB adults. Findings from the study revealed that a period (≥2 mo) of chill at 12.8°C is required for the termination of the EAB diapause. However, chill treatment of the larvae at the near zero temperature (1.7°C) does not result in the post-diapause larval development to adults, regardless of the chill time (1-9 mo). In addition, our results showed that chill treatment of immature young larvae (L1-L4 prior to JL) results in little production of EAB adults, indicating that EAB diapause predominantly as JL. Findings of this study may be useful to laboratory rearing of EAB from eggs through continuous generations and help us understand the pest's voltinism resulting from the diapause and post-diapause development under different climatic conditions.

Changes in hardwood sawtimber growth, mortality, and removals in the eastern United States

An examination of changes in growth, mortality, and removals of hardwood sawtimber in the eastern United States within the first two decades of the 21st century found large variations among regions and species groups. Changes in growth ranged from a 17% increase in the Lake States region to a statistically insignificant 1% in the Southern region. Most regions had relatively large increases in mortality. High levels of ash (Fraxinus spp.) mortality in the Northeast, Lake States, and Central regions likely were a result of the emerald ash borer (Agrilus planipennis). Hardwood sawtimber removals declined in all regions except the Lake States and Central regions, with the largest relative declines occurring in the Southern and Mid-Atlantic regions. With the exception of ash, there were no indications of immediate declines in eastern sawtimber volume. However, continual increases in mortality, a resurgence of removals, and reduced growth could cause sawtimber volume to plateau in the coming decades. The findings from this study indicated that there likely would be variations in these plateaus among the species groups and regions.

Estimated Impacts of Emerald Ash Borer on Ash Timber Supply in Texas, USA

Abstract We estimated annual timber growth, removals, and mortalities under various scenarios of the spread of emerald ash borer (Agrilus planipennis Fairmaire; EAB) within Texas. Future annual ash EAB-induced mortalities were simulated to follow either a normal or beta distribution over 25, 50, or 75 years, with five percent of the original inventory remaining at the conclusion of each projection. Discounted present values of future ash growth, harvests, mortalities, salvage, and beginning and ending annual inventories were calculated, and economic impacts to timber receipts were determined from average real prices. The present net effects of timber product output, mortalities, and salvage resulted in benefits ranging from lows of (delivered/stumpage) $37.6/$12.8 million over 25 years when assuming a normal distribution to highs of $247.8/$97.2 million over 75 years under a beta distribution. Salvage intensity exceeded mortality accumulation by a factor of at least 2.00. Regardless of length chosen, mortality that skewed toward later years led to lower discounted volumes and less value lost to EAB. Results were sensitive to discount rate selection (constant, increasing, distributional) with the constant and increasing rates having the most similar results. Longer time horizons led to far smaller losses of overall economic returns allowing more typical harvest management despite EAB.

Pest survey card on Agrilus planipennis

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017–0137), at the request of the European Commission. Its purposeisto guide the Member States in preparing data and information forAgrilus planipennis surveys. These are required to design statistically sound and risk-based pest surveys, in line with current international standards.The buprestid beetle A. planipennis is a highly destructive Union quarantine and priority pest of ashtrees (Fraxinus spp.) native to Asia. The pest has ravaged ash resources in North America and is currently spreading in European Russia and eastern Ukraine.The introduction of plant material of host taxa into EU Member States from areas where the pest is present is regulated.All European Fraxinusspecies are suitable hosts. Larvae feed on the phloem of infested ash causing extensive dieback and tree death. The beetle requires one year to complete one generation,ortwo years in colder climates. Adults are found in spring and summer. Climatic conditions in the EU territories are suitable for the establishment of A.planipennis and host trees are widely available across the EU in forests,parks and cities.The pest spreads by active flight and human-assisted dispersalat an average rate of 1,500 m per year. Infested trees show distinctivesymptoms and signs, but due to their late appearance surveillance based on symptoms is not suited for detection at low insect densities. The use of traps baited with attractants targeting adult beetles is an effective method to detect the pest at early stages of the infestation and is the recommended approach for implementing surveillance within the EU. The updated pest survey card for Agrilus planipennis is published and available online in the EFSA Plant Pest Survey Cards Gallery at the following link:https://arcg.is/09S94u

Determination of the Homing Range of Cerceris fumipennis (Hymenoptera: Crabonidae)

Cerceris fumipennis (Hymenoptera, Crabronidae) is a ground-dwelling wasp species that provisions its nests with wood-boring jewel beetles (Buprestidae), making it a useful tool for biosurveillance of buprestid forest pests, particularly the Emerald Ash Borer (Agrilus planipennis). The maximum foraging range of C. fumipennis has not yet been determined, but there have been limited studies on how far these wasps may fly when released from measured distances – an indication of their potential homing range. Careless (2008) determined the maximum homing range to be 2 km and hypothesized that the foraging range was limited to this distance. This study was coarsely-grained in that the wasps were released only at 1 km increments up to 3 km. Our study is finer-grained due to the release of wasps at intermediate distances within 3 km from the nesting area. Over 50% of the individuals released from 2.5 km and 3 km returned, indicating that the homing range of C. fumipennis is larger than previously estimated. The implications of this larger homing range and its effects on current predictions of foraging range are discussed.

Microbial Control of the Emerald Ash Borer (Coleoptera: Buprestidae) Using Beauveria bassiana (Hypocreales: Cordycipitaceae) by the Means of an Autodissemination Device.

The FraxiProtec, an autodissemination device loaded with the fungus Beauveria bassiana isolate CFL-A, was tested in the field to evaluate its potential to infect emerald ash borer adults and reduce their populations. During the 2-yr experimental period, the dispersion of B. bassiana-infected adults was also documented to assess the dissemination capacity of the biocontrol agent beyond the treated areas. The mean percentage of infected emerald ash borer in 2017 and 2018 in 15 treated sites was 43.3 ± 2.9% and 39.7 ± 3.9%, respectively, and no significant variation was observed over the tested years. Furthermore, a 40% significant reduction of the mean emerald ash borer population growth per tree in treated sites was recorded when compared to the control sites. Emerald ash borer infected with B. bassiana isolate CFL-A were collected from baited sticky traps in the sentinel stations in the area surrounding the FraxiProtec-treated sites. Even at a distance of 125 m, an average of 9.4 ± 2.6% infected emerald ash borer were collected. Finally, exploratory analyzes were carried out on parameters such as the area to be treated, ash tree density, and FraxiProtec density to document potential relationships, which could be used in the determination of a prescription.

Factors Associated With Diversity and Distribution of Buprestid Prey Captured by ForagingCerceris fumipennis(Hymenoptera: Crabronidae)

Many jewel beetles (Coleoptera: Buprestidae) play an important ecological role in wood decomposition and nutrient cycling. Compared with other saproxylic species, buprestids are considered cryptic as they are difficult to sample and identify. As a result, factors that influence buprestid diversity and distribution are poorly understood. This is especially true in urban forests, which may be uniquely fragmented and contain unique species distributions. We utilized the native ground nesting hunting wasp Cerceris fumipennis Say to survey buprestids at 20 urban sites in Minnesota. We collected a total of 1,939 beetles consisting of 11 genera and 51 species, including 9 new state records for the state of Minnesota. We found a positive relationship between wasp size and size of beetle prey captured. Agrilus was the most common genus collected, followed by Dicerca. Species richness tended to decrease in sites with many emerald ash borers, Agrilus planipennis Fairmaire, which may reflect a potential tendency of wasps to return preferentially to high-density infestations of emerald ash borers. We found buprestid species richness positively correlated with site-level variables such as the number of dead trees within a 200 m radius around each C. fumipennis nesting site. Our work illustrates how C. fumipennis can be utilized for general buprestid surveys in urban areas to better understand the distribution of this cryptic family.

Host Overwintering Phenology and Climate Change Influence the Establishment of Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), a Larval Parasitoid Introduced for Biocontrol of the Emerald Ash Borer.

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is one of the most serious forest pests in the United States. Ongoing research indicates that establishment of larval parasitoids depends upon the season-long availability of host stages susceptible to parasitism. We monitored emerald ash borer overwintering stages at 90 sites across 22 states to: 1) produce a model of the percentage of emerald ash borer overwintering as non-J larvae; 2) link that model to establishment of Tetrastichus planipennisi; and 3) explore changes to our model under climate change scenarios. Accumulated growing degree days (GDD) is an important predictor of the proportion of emerald ash borer overwintering as non-J larvae (1-4 instar larvae under the bark; available to parasitoids emerging in spring) versus J-larvae (fourth-instar larvae in pupal chambers in the outer wood; unavailable to parasitoids). From north to south, the availability of non-J emerald ash borer larvae in the spring decreases as accumulated GDD increases. In areas where the model predicted >46-75%, >30-46%, >13-30%, or ≤13% of emerald ash borer overwintering as non-J larvae, the probability of establishment of T. planipennisi was 92%, 67%, 57%, and 21%, respectively. We determined that 13% of emerald ash borer overwintering as non-J larvae was the lowest threshold for expected T. planipennisi establishment. Additional modeling predicts that under climate change, establishment of T. planipennisi will be most affected in the Central United States, with areas that are currently suitable becoming unsuitable. Our results provide a useful tool for the emerald ash borer biological control program on how to economically and successfully deploy emerald ash borer biological control agents.

A Multistage Stochastic Programming Approach to the Optimal Surveillance and Control of the Emerald Ash Borer in Cities

Emerald ash borer (EAB), a wood-boring insect native to Asia and invading North America, has killed untold millions of high-value ash trees that shade streets, homes, and parks and caused significant economic damage in cities of the United States. Local actions to reduce damage include surveillance to find EAB and control to slow its spread. We present a multistage stochastic mixed-integer programming (M-SMIP) model for the optimization of surveillance, treatment, and removal of ash trees in cities. Decision-dependent uncertainty is modeled by representing surveillance decisions and the realizations of the uncertain infestation parameter contingent on surveillance as branches in the M-SMIP scenario tree. The objective is to allocate resources to surveillance and control over space and time to maximize public benefits. We develop a new cutting-plane algorithm to strengthen the M-SMIP formulation and facilitate an optimal solution. We calibrate and validate our model of ash dynamics using seven years of observational data and apply the optimization model to a possible infestation in Burnsville, Minnesota. Proposed cutting planes improve the solution time by an average of seven times over solving the original M-SMIP model without cutting planes. Our comparative analysis shows that the M-SMIP model outperforms six different heuristic approaches proposed for the management of EAB. Results from optimally solving our M-SMIP model imply that under a belief of infestation, it is critical to apply surveillance immediately to locate EAB and then prioritize treatment of minimally infested trees followed by removal of highly infested trees. Summary of Contributions: Emerald ash borer (EAB) is one of the most damaging invasive species ever to reach the United States, damaging millions of ash trees. Much of the economic impact of EAB occurs in cities, where high-value ash trees grow in abundance along streets and in yards and parks. This paper addresses the joint optimization of surveillance and control of the emerald ash borer invasion, which is a novel application for the INFORMS society because, to our knowledge, this specific problem of EAB management has not been published before in any OR/MS journals. We develop a new multi-stage stochastic mixed-integer programming (MSS-MIP) formulation, and we apply our model to surveillance and control of EAB in cities. Our MSS-MIP model aims to help city managers maximize the net benefits of their healthy ash trees by determining the optimal timing and target population for surveying, treating, and removing infested ash trees while taking into account the spatio-temporal stochastic growth of the EAB infestation. We develop a new cutting plane methodology motivated by our problem, which could also be applied to other stochastic MIPs. Our cutting plane approach provides significant computational benefit in solving the problem. Specifically, proposed cutting planes improve the solution time by an average of seven times over solving the original M-SMIP model without cutting planes. We calibrate and validate our model using seven years of ash infestation observations in forests near Toledo, Ohio. We then apply our model to an urban forest in Burnsville, Minnesota, that is threatened by EAB. Our results provide insights into the optimal timing and location of EAB surveillance and control strategies.

Light Limitation Impacts Growth but Not Constitutive or Jasmonate Induced Defenses Relevant to Emerald Ash Borer (Agrilus planipennis) in White Fringetree (Chionanthus virginicus) or Black Ash (Fraxinus nigra).

White fringetree is a host for the invasive emerald ash borer (EAB) but is of lower quality than the related and highly susceptible black ash. Field observations suggest that host trees grown in full sun are more resistant to EAB than those in shade, however the impact of light limitation on chemical defenses has not been assessed. We quantified constitutive and jasmonate-induced phloem defenses and growth patterns of white fringetree and black ash under differential light conditions and related them to EAB larval performance. White fringetree had significantly lower constitutive and induced activities of peroxidase, polyphenol oxidase, β-glucosidase, chitinase and lignin content, but significantly higher gallic acid equivalent soluble phenolic, soluble sugar, and oleuropein concentrations compared to black ash. Multivariate analyses based on tissue chemical attributes displayed clear separation of species and induced defense responses. Further, EAB performed significantly worse on white fringetree than black ash, consistent with previous studies. Light limitation did not impact measured defenses or EAB larval performance, but it did decrease current year growth and increase photosynthetic efficiency. Overall our results suggest that phenolic profiles, metabolite abundance, and growth traits are important in mediating white fringetree resistance to EAB, and that short-term light limitation does not influence phloem chemistry or larval success.

Herb-Layer Dynamics in an Old-Growth Forest: Vegetation–Environment Relationships and Response to Invasion-Related Perturbations

Temperate forests of eastern North America are subject to multiple invasions from non-native species that have the potential to drive long-term dynamics in biodiversity. Garlic mustard (Alliaria petiolata (M. Bieb.) Cavara and Grande) is an invasive plant in many deciduous forests, and management efforts often focus on removing this species to initiate native species restoration. Agrilus planipennis Fairmaire (emerald ash borer; Coleoptera: Buprestidae) is a non-native insect pest that has caused substantial loss of ash trees (Fraxinus spp. L.) in North America. Our goal was to understand how the herbaceous layer in an old-growth forest responded to the removal of a significant invasion of A. petiolata and the loss of Fraxinus spp. due to A. planipennis. Herbaceous diversity and environmental parameters were measured in 32 permanent plots (1 m2 each) from 2012 to 2020 in an old-growth forest remnant that had experienced A. petiolata invasion and subsequent removal as well as mortality of Fraxinus spp. due to A. planipennis. Near-total loss of Fraxinus spp. as a canopy tree was not associated with changes in the understory light environment, possibly due to rapid canopy closure by adjacent trees not susceptible to the insect. Alliaria petiolata removal was associated with changes in herbaceous species richness and possibly shifts in individual species importance. Vegetation–environment relationships remained stable throughout the sampling period, suggesting that resource-related factors that structure the herb layer prevailed throughout the changes associated with Fraxinus spp. mortality and A. petiolata management. From a natural area management perspective, our data offer support for the idea that A. petiolata removal influences herb-layer diversity and indicate that in stands with a diverse tree community, the loss of Fraxinus spp. may not directly influence understory biodiversity.

Regeneration responses in black ash (Fraxinus nigra) wetlands: implications for forest diversification to address emerald ash borer (Agrilus planipennis)

Emerald ash borer (EAB) (Agrilus planipennis) has had an extensive impact across North America. It is currently present in Minnesota, USA but has not been observed in northern portions of the state where the vast majority of black ash (Fraxinus nigra) trees are located. Unlike other ash forest communities, the black ash forest type occurs in wetlands and is dominated by black ash with few associate species. Because of this, the loss of black ash can result in changes to the hydrological regime and species composition. The goal of this study was to quantify the structure and composition of regeneration 5 to 11 years post-harvest in three silvicultural systems (group selection, clearcut, and diameter-limit harvesting) to evaluate the potential for establishment of other tree species. Overall, regeneration post-harvest was high but variable across all systems. Across silvicultural systems, there was no significant relationships between residual overstory trees (> 10 cm dbh) basal area and non-ash regeneration TPH, indicating flexibility in designing treatments for diversification. Populus sapling (2.54–10 cm) density was significantly negatively correlated to the depth of the soil muck layer. In contrast, a positive relationship was observed between depth of the soil muck and black ash saplings. These findings indicate that specific silvicultural systems in combination with site quality (e.g., clearcuts on high-quality sites with shallow muck layers) may help to promote non-ash species in black ash forests that are threatened with EAB.

Population dynamics of ash across the eastern USA following invasion by emerald ash borer

Non-native insects and pathogens can alter the composition and successional trajectories of forests and, in exceptional cases, drive their host trees functionally extinct. Emerald ash borer has killed millions of ash trees in its invaded range across eastern North America. Predicting the future ecological role of ash requires information on the extent of ash regeneration and recruitment in the wake of invasion. Variable levels of ash regeneration have been observed in stands invaded by emerald ash borer, although recruitment rates of young ash trees into the overstory remain unclear. Here, we used forest inventory data to quantify ash recruitment and regeneration across the eastern United States, and we linked these observed patterns to emerald ash borer invasion history. Inventory data from 2013-2018 indicate there has been extensive ash regeneration in invaded regions, totaling > 1,200 seedlings per ha in counties invaded in 2002–2006. Plots in counties with the longest invasion histories contained the highest densities of ash seedlings and saplings, likely due to the high densities of overstory ash in these areas prior to invasion by emerald ash borer. Seedling densities also remained generally unchanged between inventory periods ending in 2007 and 2018 irrespective of invasion history. Despite this widespread regeneration, ash trees in the smallest overstory class died at faster rates than they were recruited from seedlings or saplings, resulting in negative population trajectories on plots that have been invaded for more than ~ 10 years. This trend suggests that ash will continue to decline in abundance and may become functionally extinct across the invaded range of emerald ash borer. However, the future ecological role of ash will ultimately be determined by the iterative production and survival of ash seeds to reproductive ages in the presence of emerald ash borer populations, along with effective management practices.

Go big or go home: A model-based assessment of general strategies to slow the spread of forest pests via infested firewood.

Invasive pests, such as emerald ash borer or Asian longhorn beetle, have been responsible for unprecedented ecological and economic damage in eastern North America. These and other wood-boring invasive insects can spread to new areas through human transport of untreated firewood. Behaviour, such as transport of firewood, is affected not only by immediate material benefits and costs, but also by social forces. Potential approaches to reduce the spread of wood-boring pests through firewood include raising awareness of the problem and increasing the social costs of the damages incurred by transporting firewood. In order to evaluate the efficacy of these measures, we create a coupled social-ecological model of firewood transport, pest spread, and social dynamics, on a geographical network of camper travel between recreational destinations. We also evaluate interventions aimed to slow the spread of invasive pests with untreated firewood, such as inspections at checkpoints to stop the movement of transported firewood and quarantine of high-risk locations. We find that public information and awareness programs can be effective only if the rate of spread of the pest between and within forested areas is slow. Direct intervention via inspections at checkpoints can only be successful if a high proportion of the infested firewood is intercepted. Patch quarantine is only effective if sufficiently many locations can be included in the quarantine and if the quarantine begins early. Our results indicate that the current, relatively low levels of public outreach activities and lack of adequate funding are likely to render inspections, quarantine and public outreach efforts ineffective.

Protective neighboring effect from ash trees treated with systemic insecticide against emerald ash borer.

BACKGROUNDThe emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is now the most destructive invasive species in North America. While biocontrol using parasitoids shows promising results in natural forests, strategies are needed to protect high‐value trees against invasive EAB populations. Emamectin benzoate is a commonly used systemic insecticide for the protection of valuable trees. Methods that optimize its use allow for reduced quantities of insecticide to be released in the environment and save time and money in efforts to protect ash trees from EAB. We hypothesize that a treated tree can also offer a protective neighboring effect to nearby untreated ash trees, allowing for an optimized spatial planning of insecticide applications.RESULTSWe sampled 896 untreated ash trees, in the vicinity of treated trees, in Maryland and Washington DC. We recorded signs of EAB infestation (canopy condition, exit holes, wood pecks, epicormic growth, and bark splits). Two subsequent yearly samplings were made of 198 and 216 trees, respectively. We also present a novel proximity index for this particular application. Results show consistent decrease in EAB infestation signs in untreated trees as proximity to treated trees increases.CONCLUSIONResults support that a neighboring effect occurs. However, proximity to treated trees must be high for a tree to be safely left untreated. This proximity seems rare in forests, but can happen in urban/planted landscapes. Future studies should test and validate these findings, and could lead to a more precise recommended safe index tailored across multiple ash species and geographic regions.

Secondary invasion? Emerald ash borer (Agrilus planipennis) induced ash (Fraxinus spp.) mortality interacts with ecological integrity to facilitate European buckthorn (Rhamnus cathartica)

Invasive insects facilitate secondary invasive species by altering forest structure and function. Specifically, invasive insect herbivores may promote the establishment and growth of invasive plants by creating canopy gaps. Such secondary invasions may be influenced by ecological integrity — the degree to which ecosystem composition, structure, and function deviate from their natural or historical range of variation. Here we investigate (i) whether emerald ash borer (Agrilus planipennis; EAB) induced ash (Fraxinus spp.) mortality facilitates European buckthorn (Rhamnus cathartica) — an invasive, shade-tolerant shrub, and (ii) the role of ecological integrity in this relationship. We use a principal component analysis (PCA) to calculate an index of ecological integrity and a zero-altered negative binomial generalized linear mixed model (GLMM) to describe European buckthorn occurrence and abundance. European buckthorn occurrence is influenced by canopy gaps, independent of EAB-induced gap formation. Ecological integrity and EAB-induced ash mortality interact to control European buckthorn abundance, with high ecological integrity limiting EAB-facilitated buckthorn invasion. This is the first evidence for EAB-facilitated buckthorn invasion and for an interaction between a secondary invasion and ecological integrity. Thus, ecological integrity plays an important role in the EAB–buckthorn system and may be used to manage the impacts of secondary invasions.

Another Look at Systemic Neonicotinoid Applications for Emerald Ash Borer Suppression

Emerald ash borer (EAB, Agrilus planipennis) is an invasive phloem feeder from East Asia that has killed millions of ash trees in North America. Currently, effective options for individual tree protection are limited to systemic insecticides, in particular neonicotinoids, which have come under increased scrutiny for their nontarget effects. In this study, green ash (Fraxinus pennsylvanica) trees were treated with two neonicotinoid insecticides, imidacloprid and dinotefuran, at full and half label rates based on trunk diameter to evaluate residues and efficacy. Analyzing the leaf, stem, and root tissues, there was no difference in insecticide residues between application rates within each tissue type. However, there were significantly higher residues of imidacloprid in root tissue compared to other plant tissues, and dinotefuran applied at the full label rate resulted in lower residues in stem phloem tissue. Additionally, insecticide-treated stems were artificially infested with EAB eggs to measure larval success (survival and growth). EAB larvae consumed less phloem in treated trees compared to untreated controls. These findings suggest that, in small-diameter ash, lower than label-recommended doses may be a viable component of an integrated management plan for EAB.