Eradication of Invading Insect Populations: From Concepts to Applications.

Eradication is the deliberate elimination of a species from an area. Given that international quarantine measures can never be 100% effective, surveillance for newly arrived populations of nonnative species coupled with their eradication represents an important strategy for excluding potentially damaging insect species. Historically, eradication efforts have not always been successful and have sometimes been met with public opposition. But new developments in our understanding of the dynamics of low-density populations, the availability of highly effective treatment tactics, and bioeconomic analyses of eradication strategies offer new opportunities for developing more effective surveillance and eradication programs. A key component that connects these new developments is the harnessing of Allee effects, which naturally promote localized species extinction. Here we review these developments and suggest how research might enhance eradication strategies.

Nonnative forest insects and pathogens in the United States: Impacts and policy options.

We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yr. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates. Introduced insects and diseases occur in forests and cities throughout the United States, and the problem is particularly severe in the Northeast and Upper Midwest. Nonnative forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from United States forests within decades. The resulting shift in forest structure and species composition alters ecosystem functions such as productivity, nutrient cycling, and wildlife habitat. In urban and suburban areas, loss of trees from streets, yards, and parks affects aesthetics, property values, shading, stormwater runoff, and human health. The economic damage from nonnative pests is not yet fully known, but is likely in the billions of dollars per year, with the majority of this economic burden borne by municipalities and residential property owners. Current policies for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. Options are available to strengthen the defenses against pest arrival and establishment, including measures taken in the exporting country prior to shipment, measures to ensure clean shipments of plants and wood products, inspections at ports of entry, and post-entry measures such as quarantines, surveillance, and eradication programs. Improved data collection procedures for inspections, greater data accessibility, and better reporting would support better evaluation of policy effectiveness. Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions. Adopting stronger policies to reduce establishments of new forest insects and diseases would shift the major costs of control to the source and alleviate the economic burden now borne by homeowners and municipalities.

Laboratory Evaluation of the Toxicity of Systemic Insecticides to Emerald Ash Borer Larvae.

Emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), an invasive phloem-feeding insect native to Asia, threatens at least 16 North American ash (Fraxinus) species and has killed hundreds of millions of ash trees in landscapes and forests. We conducted laboratory bioassays to assess the relative efficacy of systemic insecticides to control emerald ash borer larvae in winter 2009 and 2010. Second- and third-instar larvae were reared on artificial diet treated with varying doses of emamectin benzoate (TREE-äge, Arborjet, Inc., Woburn, MA), imidacloprid (Imicide, J. J Mauget Co., Arcadia, CA), dinotefuran (Safari, Valent Professional Products, Walnut Creek, CA), and azadirachtin (TreeAzin, BioForest Technologies, Inc., Sault Ste. Marie, Ontario, and Azasol, Arborjet, Inc., Woburn, MA). All of the insecticides were toxic to emerald ash borer larvae, but lethal concentrations needed to kill 50% of the larvae (LC50), standardized by larval weight, varied with insecticide and time. On the earliest date with a significant fit of the probit model, LC50 values were 0.024 ppm/g at day 29 for TREE-äge, 0.015 ppm/g at day 63 for Imicide, 0.030 ppm/g at day 46 for Safari, 0.025 ppm/g at day 24 for TreeAzin, and 0.027 ppm/g at day 27 for Azasol. The median lethal time to kill 50% (LT50) of the tested larvae also varied with insecticide product and dose, and was longer for Imicide and Safari than for TREE-äge or the azadirachtin products. Insecticide efficacy in the field will depend on adult and larval mortality as well as leaf and phloem insecticide residues.

Emerald ash borer invasion of North America: history, biology, ecology, impacts, and management.

Since its accidental introduction from Asia, emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has killed millions of ash trees in North America. As it continues to spread, it could functionally extirpate ash with devastating economic and ecological impacts. Little was known about EAB when it was first discovered in North America in 2002, but substantial advances in understanding of EAB biology, ecology, and management have occurred since. Ash species indigenous to China are generally resistant to EAB and may eventually provide resistance genes for introgression into North American species. EAB is characterized by stratified dispersal resulting from natural and human-assisted spread, and substantial effort has been devoted to the development of survey methods. Early eradication efforts were abandoned largely because of the difficulty of detecting and delineating infestations. Current management is focused on biological control, insecticide protection of high-value trees, and integrated efforts to slow ash mortality.

Persistence and recovery of dinotefuran in eastern hemlock (Tsuga canadensis) foliage and twigs by UPLC-MS/MS and ELISA.

BACKGROUND: Dinotefuran, a systemic neonicotinoid insecticide, is approved for control of hemlock woolly adelgid (HWA) (Adelges tsugae Annand), an invasive sap-feeding insect that can kill eastern hemlocks (Tsuga canadensis). Dinotefuran is highly water soluble, facilitating more rapid translocation and HWA control than other neonicotinoids, but its persistence is not well-known. Samples of needles and twigs were collected in spring 2021 from 50 hemlocks treated with a dinotefuran basal trunk spray in 2018 or 2019 (131-145 weeks and 85-93 weeks before sampling, respectively). Processed samples were analyzed with ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) and enzyme-linked immunosorbent assays (ELISA). RESULTS: Dinotefuran residues were 4.6-6.1 times higher in needles than in twigs collected from the same trees. Average (±SE) residues in foliage samples collected from trees treated in 2019 ranged from 0.663 ± 0.243 to 0.564 ± 0.119 mg kg-1 , compared with 0.213 ± 0.033 and 0.225 ± 0.132 mg kg-1 in foliage from trees treated in 2018. Foliage residues from UPLC-MS/MS were consistently lower but strongly related to those from ELISA. Matrix effects appeared to disrupt ELISA analysis of twigs. None of the 25 trees treated in 2019 had live HWA when samples were collected in 2021 while low densities of HWA were observed on 52% of trees treated in 2018. CONCLUSIONS: Dinotefuran was recovered from hemlock foliage, and to a lesser extent twigs, >2 years post-treatment. This, along with its relatively rapid translocation, suggests dinotefuran is a viable option for protecting declining or heavily infested hemlocks from HWA. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Tree species richness and ash density have variable effects on emerald ash borer biological control by woodpeckers and parasitoid wasps in post-invasion white ash stands.

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is the most destructive insect to invade North American forests. Identifying habitat features that support EAB natural enemies is necessary to enhance EAB biological control. In many forest ecosystems, tree species diversity has been linked with reduced pest abundance and increases in natural enemy abundance. We assessed the influence of tree species richness, ash density, and proportion of total ash basal area on ash canopy condition, EAB larval densities, and biocontrol by woodpeckers and parasitoids in pairs of healthy and declining overstory (DBH > 10 cm) and recruit-sized ash (DBH 2-10 cm) in 4 post-invasion forests in Michigan, USA. Tree species richness and ash density were not significantly associated with EAB larval densities, ash canopy dieback and transparency, and woodpecker predation of EAB larvae. In declining and healthy overstory ash, woodpeckers killed 38.5 ±â€…3.9% and 13.2 ±â€…3.7% of larvae, respectively, while the native parasitoid Phasgonophora sulcata Westwood killed 15.8 ±â€…3.8% and 8.3 ±â€…3.0% and the introduced parasitoid Spathius galinae Belokobylskij & Strazanac killed 10.8 ±â€…2.5% and 5.0 ±â€…2.6% of EAB larvae. Parasitism by P. sulcata was inversely related to ash density while parasitism by S. galinae was positively associated with ash density. Ash density, but not tree diversity, appears to differentially influence biological control of EAB by parasitoids, but this effect is not associated with reduced EAB densities or improved canopy condition.

Persistence and distribution of dinotefuran in tree of heaven.

Spotted lanternfly (SLF) (Lycorma delicatula (White)), an invasive planthopper discovered in Pennsylvania, U.S.A. in 2014, feeds for approximately six months by sucking phloem sap from trunks and limbs of tree of heaven, Ailanthus altissima, along with several native trees and woody vines. Basal trunk sprays of dinotefuran, a systemic neonicotinoid insecticide, are commonly used to reduce SLF densities and spread. Information on dinotefuran persistence and within-tree distribution can help identify optimal timing of annual basal trunk sprays, facilitating efficient use of available resources. We applied dinotefuran to 20 uninfested A. altissima trees in early April then periodically sampled foliage to monitor insecticide residues. Foliar dinotefuran residues averaged (± SE) 7.8 ± 1.1 and 6.3 ± 1.2 in July and August, respectively, then dropped significantly to 2.6 ± 0.5 ppm in September. In a second study, 20 A. altissima trees were similarly treated with dinotefuran basal trunk sprays in early June. Trees were felled to collect foliage and phloem from branches and the trunk in either mid-July or September. Foliar residues averaged 12.7 ± 1.3 and 14.6 ± 2.2 ppm in July and September, respectively. For trees felled in July, residues were detected in phloem collected from below the spray line on trunks of seven trees and above the spray line on three trees, averaging 8.6 ± 4.4 and 7.4 ± 2.9 ppm, respectively. In trees felled in September, phloem from below spray lines of seven trees averaged 3.7 ± 1.3 ppm but dinotefuran was not detected in phloem from above the spray line on any trees. Dinotefuran was not detected in phloem sampled from any branches in either July or September. Results suggest dinotefuran basal trunk sprays applied between late May and mid June should persist long enough to effectively control SLF late instars and adults.

Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams.

Emerald ash borer (EAB) has killed millions of ash trees in the United States and Canada, yet impacts on terrestrial-aquatic linkages are largely unknown. Ash tree death along streams creates canopy gaps, increasing light to riparian plants and potentially affecting organic matter subsidies. Six EAB-related canopy gaps along streams across a gradient of timing of EAB invasion in Michigan were characterized for coarse woody material (CWM), terrestrial and aquatic leaf litter and their associated bacterial communities, and macroinvertebrates upstream, downstream, and at the center of the gap. Stream sites downstream of EAB-related canopy gaps had significantly lower dissolved oxygen and macroinvertebrate diversity than sites upstream and at the gaps. Yet there was no difference in CWM or aquatic leaf litter, likely due to downstream movement of organic matter from upstream riparian sources. Low abundance bacterial amplicon sequence variants unique to gap or forest were detected in leaves and leaf litter, suggesting that EAB-related canopy gaps altered leaf-associated bacterial communities. Overall, EAB invasion indirectly impacted some variables, while organic matter dynamics were resistant to change.

A comparison of trap type and height for capturing cerambycid beetles (Coleoptera).

Wood-boring beetles in the family Cerambycidae (Coleoptera) play important roles in many forest ecosystems. However, increasing numbers of invasive cerambycid species are transported to new countries by global commerce and threaten forest health in the United States and worldwide. Our goal was to identify effective detection tools for a broad array of cerambycid species by testing some known cerambycid attractants and a pheromone in different trap designs placed across a range of habitats. We compared numbers and species richness of cerambycid beetles captured with cross-vane panel traps and 12-unit Lindgren multiple-funnel traps, placed either at ground level (1.5 m high) or canopy level (approximately 3-10 m high), at eight sites classified as either residential, industrial, deciduous forest, or conifer forest. We captured 3,723 beetles representing 72 cerambycid species from 10 June to 15 July 2010. Species richness was highest for the subfamilies Cerambycinae and Lamiinae, which accounted for 33 and 46% of all species captured, respectively. Overall, the cross-vane panel traps captured approximately 1.5 times more beetles than funnel traps. Twenty-one species were captured exclusively in traps at one height, either in the canopy or at ground level. More species were captured in hardwood sites (59 species) where a greater diversity of host material was available than in conifer (34 species), residential (41 species), or industrial (49) sites. Low numbers of beetles (n < 5) were recorded for 28 of the beetle species. The number of species captured per week ranged from 49 species on 21 June to 37 species on 12 July. Cross-vane panel traps installed across a vertical gradient should maximize the number of cerambycid species captured.

Combining tactics to exploit Allee effects for eradication of alien insect populations.

Invasive species increasingly threaten ecosystems, food production, and human welfare worldwide. Hundreds of eradication programs have targeted a wide range of nonnative insect species to mitigate the economic and ecological impacts of biological invasions. Many such programs used multiple tactics to achieve this goal, but interactions between tactics have received little formal consideration, specifically as they interact with Allee dynamics. If a population can be driven below an Allee threshold, extinction becomes more probable because of factors such as the failure to find mates, satiate natural enemies, or successfully exploit food resources, as well as demographic and environmental stochasticity. A key implication of an Allee threshold is that the population can be eradicated without the need and expense of killing the last individuals. Some combinations of control tactics could interact with Allee dynamics to increase the probability of successful eradication. Combinations of tactics can be considered to have synergistic (greater efficiency in achieving extinction from the combination), additive (no improvement over single tactics alone), or antagonistic (reduced efficiency from the combination) effects on Allee dynamics. We highlight examples of combinations of tactics likely to act synergistically, additively, or antagonistically on pest populations. By exploiting the interacting effects of multiple tactics on Allee dynamics, the success and cost-effectiveness of eradication programs can be enhanced.

Phenology, Density and Parasitism of Asian Chestnut Gall Wasp (Dryocosmus kuriphilus) (Hymenoptera: Cynipidae) in Recently Invaded Chestnut (Castanea spp.) Orchards in Michigan.

Asian chestnut gall wasp (ACGW) (Dryocosmus kuriphilus Yasumatsu), an invasive pest native to China, was detected in Michigan, the largest chestnut producer in North America, in 2015. Along with quantifying gall densities, we tracked dates and cumulative growing degree days corresponding to ACGW life stages in five, seven, and nine orchards in 2017-2019, respectively. Gall formation, triggered by the onset of feeding by overwintered larvae, began soon after bud break. Most adult wasps emerged in mid summer, after pollen production peaked. Density of ACGW in all sites dropped sharply in 2019, probably as a result of larval mortality caused by severely cold temperatures in late January. Gall density was generally lower on Chinese chestnut (Castanea mollisima Blume) trees and C. mollisima hybrids, which share some coevolutionary history with ACGW, than on cultivars of European chestnut (C. sativa Miller) and Japanese-European (C. crenata Sieb. & Zucc. x C. sativa) trees, including the popular Colossal cultivar. Torymus sinensis Kamijo (Hymenoptera: Torymidae), a larval parasitoid previously introduced into the U.S. and several countries in Asia and Europe for ACGW biocontrol, appears to be spreading with ACGW in Michigan. Parasitoid larvae were recorded in four, six, and eight of the infested sites we sampled in 2017-2019, respectively, and parasitism rates ranged from 5 to70% of galls.

Evaluation of double-decker traps for emerald ash borer (Coleoptera: Buprestidae).

Improved detection tools are needed for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive forest insect from Asia that has killed millions of ash (Fraxinus spp.) trees in North America since its discovery in Michigan in 2002. We evaluated attraction of adult A. planipennis to artificial traps incorporating visual (e.g., height, color, silhouette) and olfactory cues (e.g., host volatiles) at field sites in Michigan. We developed a double-decker trap consisting of a 3-m-tall polyvinyl pipe with two purple prisms attached near the top. In 2006, we compared A. planipennis attraction to double-decker traps baited with various combinations of manuka oil (containing sesquiterpenes present in ash bark), a blend of four ash leaf volatiles (leaf blend), and a rough texture to simulate bark. Significantly more A. planipennis were captured per trap when traps without the rough texture were baited with the leaf blend and manuka oil lures than on traps with texture and manuka oil but no leaf blend. In 2007, we also tested single prism traps set 1.5 m above ground and tower traps, similar to double-decker traps but 6 m tall. Double-decker traps baited with the leaf blend and manuka oil, with or without the addition of ash leaf and bark extracts, captured significantly more A. planipennis than similarly baited single prism traps, tower traps, or unbaited double-decker traps. A baited double-decker trap captured A. planipennis at a field site that was not previously known to be infested, representing the first detection event using artificial traps and lures. In 2008, we compared purple or green double-decker traps, single prisms suspended 3-5 m above ground in the ash canopy (canopy traps), and large flat purple traps (billboard traps). Significantly more A. planipennis were captured in purple versus green traps, baited traps versus unbaited traps, and double-decker versus canopy traps, whereas billboard traps were intermediate. At sites with very low A. planipennis densities, more A. planipennis were captured on baited double-decker traps than on other traps and a higher percentage of the baited double-decker traps captured beetles than any other trap design. In all 3 yr, peak A. planipennis activity occurred during late June to mid-July, corresponding to 800-1200 growing degree-days base 10 degrees C (DD10). Nearly all (95%) beetles were captured by the end of July at approximately 1400 DD10.

Evaluation of Agrilus planipennis (Coleoptera: Buprestidae) control provided by emamectin benzoate and two neonicotinoid insecticides, one and two seasons after treatment.

Effective methods are needed to protect ash trees (Fraxinus spp.) from emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive buprestid that has killed millions of North American ash (Fraxinus spp.) trees. We randomly assigned 175 ash trees (11.5-48.1 cm in diameter) in 25 blocks located in three study sites in Michigan to one of seven insecticide treatments in May 2007. Treatments included 1) trunk-injected emamectin benzoate; 2) trunk-injected imidacloprid; 3) basal trunk spray of dinotefuran with or 4) without Pentra-Bark, an agricultural surfactant; 5) basal trunk spray of imidacloprid with or 6) without Pentra-Bark; or (7) control. Foliar insecticide residues (enzyme-linked immunosorbent assay) and toxicity of leaves to adult A. planipennis (4-d bioassays) were quantified at 3-4-wk intervals posttreatment. Seven blocks of trees were felled and sampled in fall 2007 to quantify A. planipennis larval density. Half of the remaining blocks were retreated in spring 2008. Bioassays and residue analyses were repeated in summer 2008, and then all trees were sampled to assess larval density in winter. Foliage from emamectin benzoate-treated trees was highly toxic to adult A. planipennis, and larval density was < 1% of that in comparable control trees, even two seasons posttreatment. Larval densities in trees treated with trunk-injected imidacloprid in 2007 + 2008 were similar to control trees. Dinotefuran and imidacloprid were effectively translocated within trees treated with the noninvasive basal trunk sprays; the surfactant did not appreciably enhance A. planipennis control. In 2008, larval densities were 57-68% lower in trees treated with dinotefuran or imidacloprid trunk sprays in 2007 + 2008 than on controls, but densities in trees treated only in 2007 were similar to controls. Highly effective control provided by emamectin benzoate for > or = 2 yr may reduce costs or logistical issues associated with treatment.

The influence of satellite populations of emerald ash borer on projected economic costs in U.S. communities, 2010-2020.

The invasion spread of the emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is characterized by the formation of satellite populations that expand and coalesce with the continuously invading population front. As of January 2010, satellite infestations have been detected in 13 states and two Canadian provinces. Understanding how newly established satellite populations may affect economic costs can help program managers to justify and design prevention and control strategies. We estimate the economic costs caused by EAB for the 10-yr period from 2010 to 2020 for scenarios of fewer EAB satellite populations than those found from 2005 to 2010 and slower expansion of satellite populations found in 2009. We measure the projected discounted cost of treatment, removal, and replacement of ash trees (Fraxinus spp.) growing in managed landscapes in U.S. communities. Estimated costs for the base scenario with the full complement of satellites in 2005-2010 and no program to mitigate spread is $12.5 billion. Fewer EAB satellites from 2005 to 2010 delay economic costs of $1.0 to 7.4 billion. Slower expansion of 2009 satellite populations delays economic costs of $0.1 to 0.7 billion. Satellite populations that are both distant from the core EAB infestation and close to large urban areas caused more economic costs in our simulations than did other satellites. Our estimates of delayed economic costs suggest that spending on activities that prevent establishment of new satellite EAB populations or slow expansion of existing populations can be cost-effective and that continued research on the cost and effectiveness of prevention and control activities is warranted.

Evaluation of Trapping Schemes to Detect Emerald Ash Borer (Coleoptera: Buprestidae).

Management responses to invasive forest insects are facilitated by the use of detection traps ideally baited with species-specific semiochemicals. Emerald ash borer, Agrilus planipennis Fairmaire, is currently invading North American forests, and since its detection in 2002, development of monitoring tools has been a primary research objective. We compared six trapping schemes for A. planipennis over 2 yr at sites in four U.S. states and one Canadian province that represented a range of background A. planipennis densities, canopy coverage, and ash basal area. We also developed a region-wide phenology model. Across all sites and both years, the 10th, 50th, and 90th percentile of adult flight occurred at 428, 587, and 837 accumulated degree-days, respectively, using a base temperature threshold of 10°C and a start date of 1 January. Most trapping schemes captured comparable numbers of beetles with the exception of purple prism traps (USDA APHIS PPQ), which captured significantly fewer adults. Trapping schemes varied in their trap catch across the gradient of ash basal area, although when considering trap catch as a binary response variable, trapping schemes were more likely to detect A. planipennis in areas with a higher ash component. Results could assist managers in optimizing trap selection, placement, and timing of deployment given local weather conditions, forest composition, and A. planipennis density.

Species Diversity and Assemblages of Cerambycidae in the Aftermath of the Emerald Ash Borer (Coleoptera: Buptrestidae) Invasion in Riparian Forests of Southern Michigan.

Extensive ash (Fraxinus spp.) mortality has been reported across much of the area in eastern North America invaded by emerald ash borer (Agrilus planipennis Fairmaire), but indirect effects of emerald ash borer invasion on native forest insects are not well-studied. We assessed cerambycid beetle (Coleoptera: Cerambycidae) species captured in baited cross-vane panel traps during the 2017 and 2018 growing seasons. Traps were placed in 12 riparian forest sites distributed across three watersheds selected to represent the temporal gradient of the emerald ash borer invasion from southeastern to southwestern Michigan. Although ash species originally dominated overstory vegetation in all sites, >85% of ash basal area has been killed by emerald ash borer. We captured a total of 3,645 beetles representing 65 species and five subfamilies. Species assemblages in southeast sites, with the longest history of emerald ash borer invasion, differed from those in south central and southwest Michigan, which were similar. These differences were largely due to three species, which accounted for >60% of beetle captures in southeast Michigan. Associations among site-related variables and beetle captures indicated cerambycid species assemblages were associated most strongly with abundance and decay stage of coarse woody debris. During both years, >90% of cerambycid species were captured by mid-summer but seasonal activity differed among and within tribes. Numbers of beetles captured by canopy and ground traps were similar but species richness was higher in canopy traps than ground traps. Results suggest inputs of emerald ash borer-killed ash can have temporally lagged, secondary effects on cerambycid communities.

Emerald Ash Borer (Coleoptera: Buprestidae) Densities Over a 6-yr Period on Untreated Trees and Trees Treated With Systemic Insecticides at 1-, 2-, and 3-yr Intervals in a Central Michigan Forest.

We assessed density of emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) larvae over a 6-yr period by felling and sampling a total of 315 green ash (Fraxinus pennsylvanica Marsh.) trees that were left untreated or treated with imidacloprid, dinotefuran, or emamectin benzoate products at 1-yr, 2-yr, or 3-yr intervals. Our study, conducted across a 32-ha forested area, began soon after emerald ash borer became established and continued through the peak and eventual decline of the emerald ash borer population. Less than half of the 96 trees in the pretreatment sample were infested and larval densities were very low. Densities of emerald ash borer remained low for 3 yr, then increased exponentially, eventually resulting in mortality of most untreated overstory ash. Trees treated with either low or moderate rates of emamectin benzoate applied via trunk injection had few or no emerald ash borer galleries, even 3 yr post-treatment. Basal trunk sprays of dinotefuran applied annually were also effective at preventing larval densities from reaching damaging levels. Average larval densities on trees treated with a trunk injection of imidacloprid were lower but did not differ from untreated trees, regardless of treatment frequency. Larval parasitism was rare, while woodpecker predation was common and accounted for nearly all natural larval mortality, even on trees with very low densities of larvae.

Host range of the emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) in North America: results of multiple-choice field experiments.

Emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), an invasive phloem-feeding pest, was identified as the cause of widespread ash (Fraxinus) mortality in southeast Michigan and Windsor, Ontario, Canada, in 2002. A. planipennis reportedly colonizes other genera in its native range in Asia, including Ulmus L., Juglans L., and Pterocarya Kunth. Attacks on nonash species have not been observed in North America to date, but there is concern that other genera could be colonized. From 2003 to 2005, we assessed adult A. planipennis landing rates, oviposition, and larval development on North American ash species and congeners of its reported hosts in Asia in multiple-choice field studies conducted at several southeast Michigan sites. Nonash species evaluated included American elm (U. americana L.), hackberry (Celtis occidentalis L.), black walnut (J. nigra L.), shagbark hickory [Carya ovata (Mill.) K.Koch], and Japanese tree lilac (Syringa reticulata Bl.). In studies with freshly cut logs, adult beetles occasionally landed on nonash logs but generally laid fewer eggs than on ash logs. Larvae fed and developed normally on ash logs, which were often heavily infested. No larvae were able to survive, grow, or develop on any nonash logs, although failed first-instar galleries occurred on some walnut logs. High densities of larvae developed on live green ash and white ash nursery trees, but there was no evidence of larval survival or development on Japanese tree lilac and black walnut trees in the same plantation. We felled, debarked, and intensively examined >28 m2 of phloem area on nine American elm trees growing in contact with or adjacent to heavily infested ash trees. We found no sign of A. planipennis feeding on any elm.

Density of Emerald Ash Borer (Coleoptera: Buprestidae) Adults and Larvae at Three Stages of the Invasion Wave.

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), an invasive phloem-feeding buprestid, has killed hundreds of millions of ash (Fraxinus spp.) trees in the United States and two Canadian provinces. We evaluated EAB persistence in post-invasion sites and compared EAB adult captures and larval densities in 24 forested sites across an east-west gradient in southern Michigan representing the Core (post-invasion), Crest (high EAB populations), and Cusp (recently infested areas) of the EAB invasion wave. Condition of green ash (Fraxinus pennsylvanica Marsh) trees were recorded in fixed radius plots and linear transects in each site. Ash mortality was highest in Core sites in the southeast, moderate in Crest sites in central southern Michigan, and low in Cusp sites in the southwest. Traps and trap trees in Crest sites accounted for 75 and 60% of all EAB beetles captured in 2010 and 2011, respectively. Populations of EAB were present in all Core sites and traps in these sites captured 13% of all beetles each year. Beetle captures and larval densities at Cusp sites roughly doubled between 2010 and 2011, reflecting the increasing EAB populations. Sticky bands on girdled trees captured the highest density of EAB beetles per m2 of area, while baited double-decker traps had the highest detection rates and captured the most beetles. Larval densities were higher on girdled ash than on similar ungirdled trees and small planted trees. Woodpecker predation and a native larval parasitoid were present in all three invasion regions but had minor effects on ash survival and EAB densities.

Estimating potential emerald ash borer (Coleoptera: Buprestidae) populations using ash inventory data.

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), a phloem-feeding pest native to Asia, was identified in June 2002 as the cause of widespread ash (Fraxinus spp.), mortality in southeastern Michigan and Windsor, Ontario, Canada. Localized populations of A. planipennis have since been found across lower Michigan and in areas of Ohio, Indiana, Illinois, Maryland, and Ontario. Officials working to contain A. planipennis and managers of forestlands near A. planipennis infestations must be able to compare alternative strategies to allocate limited funds efficiently and effectively. Empirical data from a total of 148 green ash, Fraxinus pennsylvanica Marsh., and white ash, Fraxinus americana L., trees were used to develop models to estimate surface area of the trunk and branches by using tree diameter at breast height (dbh). Data collected from 71 additional F. pennsylvanica and F. americana trees killed by A. planipennis showed that on average, 88.9 +/- 4.6 beetles developed and emerged per m2 of surface area. Models were applied to ash inventory data collected at two outlier sites to estimate potential production of A. planipennis beetles at each site. Large trees of merchantable size (dbh > or = 26 cm) accounted for roughly 6% of all ash trees at the two sites, but they could have contributed 55-65% of the total A. planipennis production at both sites. In contrast, 75- 80% of the ash trees at the outlier sites were < or =13 cm dbh, but these small trees could have contributed only < or =12% of the potential A. planipennis production at both sites. Our results, in combination with inventory data, can be used by regulatory officials and resource managers to estimate potential A. planipennis production and to compare options for reducing A. planipennis density and slowing the rate of spread for any area of interest.