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.

Enantiomeric composition of α-pinene affects catches of bark and wood boring beetles, and associated species, in ethanol-baited multiple-funnel traps.

In 2009, we determined the effects of the enantiomeric composition of the kairomone, α-pinene, on trap catches of arboreal beetles (Coleoptera) in stands of eastern pine trees with resin dominated by (+)-α-pinene. We hypothesized that the responses of beetles would correlate with the predominant enantiomer of α-pinene found in host pines. Lures of (+)-, racemic (±), and (-)-α-pinene were added separately to ethanol-baited multiple-funnel traps. Species such as Monarthrum mali (Fitch), Dendroctonus terebrans (Olivier), Ips grandicollis (Eichhoff), and Pachylobius picivorus (Germar) (Coleoptera: Curculionidae) showed a preference for traps co-baited with (-)-α-pinene. α-Pinene enhanced attraction of Hylastes salebrosus Eichhoff, Hylastes porculus Erickson and Hylastes tenuis Eichhoff (Coleoptera: Curculionidae) to ethanol-baited traps with no effects from enantiomeric composition of α-pinene. The attraction of the ambrosia beetles, Xyleborinus saxesenii (Ratzeburg) and Dryoxylon onoharaense (Murayama) (Coleoptera: Curculionidae) to ethanol-baited traps was interrupted by the addition of α-pinene, regardless of enantiomeric composition. Species such as Xylosandrus germanus (Blandford), Cnestus mutilatus (Blandford) and Stenoscelis brevis (Boheman) (Coleoptera: Curculionidae) were unaffected by the presence of α-pinene. Trap catches of some species of longhorn beetles and bark beetle predators (Coleoptera: Cerambycidae, Cleridae, Elateridae, Histeridae, and Trogossitidae) were increased by the addition of α-pinene, although results varied by location. Platysoma spp. (Coleoptera: Histeridae) showed a marked preference for traps co-baited with (+)-α-pinene in Florida and Georgia. In summary, we found that the enantiomeric composition of α-pinene in hosts was not a good predictor of enantiomeric preferences by beetles.

Successful establishment, spread, and impact of the introduced parasitoid Spathius galinae (Hymenoptera: Braconidae) on emerald ash borer (Coleoptera: Buprestidae) populations in postinvasion forests in Michigan.

Spathius galinae is a larval parasitoid native to the Russian Far East that was approved for release in the United States in 2015 for biological control of the emerald ash borer (EAB), Agrilus planipennis, an invasive beetle from Asia responsible for widespread mortality of ash trees (Fraxinus spp.) in North America. From 2015 to 2017, 1,340-1,445 females of S. galinae along with males were released into each release plot, paired with a nonrelease control plot (1-12.5 km apart), at 6 postinvasion forested sites containing abundant pole-sized ash trees in Michigan. By 2018, S. galinae had spread to all but one control plot. Based on the first year that S. galinae was found in trees in each control plot and the distances of those trees to the parasitoid release point within each site, we estimated that S. galinae spread at 3.7 (±1.9) km per year after its initial releases in 2015. The proportion of sampled trees with S. galinae broods, brood densities within sampled trees, and parasitism of EAB larvae increased sharply in both control and release plots after the last field releases in 2017, with the highest parasitism rates (42.8-60.3%) in 2020. Life table analysis showed that S. galinae alone reduced EAB's net population growth rate by 35-55% across sites from 2018 to 2020. These results demonstrate that S. galinae has established an increasing population in Michigan and now plays a significant role in reducing EAB populations in the area.

Postrelease assessment of Oobius agrili (Hymenoptera: Encyrtidae) establishment and persistence in Michigan and the Northeastern United States.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive woodboring pest of ash trees (Fraxinus sp.) in North America. Among the Asiatic parasitoids being released for the management of EAB in North America, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) is the only EAB egg parasitoid. To date, more than 2.5 million O. agrili have been released in North America; however, few studies have examined its success as a biological control agent of EAB. We conducted studies to assess O. agrili establishment, persistence, spread, and EAB egg parasitism rates in Michigan at the earliest release sites (2007-2010), as well as at more recent release sites (2015-2016) in 3 Northeastern United States (Connecticut, Massachusetts, New York). In both regions, we documented successful O. agrili establishment at all but one release site. In Michigan, O. agrili has persisted at release sites for over a decade and spread to all control sites located 0.6-3.8 km from release sites. Overall, EAB egg parasitism ranged from 1.5% to 51.2% (mean of 21.4%) during 2016-2020 in Michigan and from 2.6% to 29.2% (mean of 16.1%) during 2018-2020 in the Northeastern states. Future research efforts should focus on factors affecting the spatiotemporal variation in EAB egg parasitism rates by O. agrili, as well as its potential range in North America.

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.

A Phenology Model for Simulating Oobius agrili (Hymenoptera: Encyrtidae) Seasonal Voltinism and Synchrony With Emerald Ash Borer Oviposition.

In North America, the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), continues to spread, and its egg parasitoid, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), is being released for emerald ash borer biocontrol well beyond their endemic climatic ranges in China. We developed a multiple cohort rate summation model to simulate O. agrili F0, F1, and F2 generations, and emerald ash borer oviposition for examining host-parasitoid synchrony across a north-south gradient from Duluth, MN (latitude 46.8369, longitude -92.1833) to Shreveport, LA (latitude 32.4469, longitude -93.8242). Temporal occurrences of critical day length for O. agrili diapause induction were integrated into the model. We used O. agrili and emerald ash borer trapping data from south central and northwestern Lower Michigan for model validation. Simulations demonstrated that 1) F0 adult emergence consistently occurred 2-5 d before emerald ash borer oviposition began; 2) F1 adult emergence was most synchronized with peak emerald ash borer oviposition compared with other generations; and 3) emerald ash borer oviposition was complete, or near so, when F2 adult emergence was predicted across the north-south gradient. Comparison of O. agrili trap captures with model simulations demonstrated that primarily two adult O. agrili generations (F0 and F1) emerged per year in Michigan and almost all F2 larvae entered diapause despite day lengths longer than critical day length in south central Michigan. Critical day length varied temporally across the north-south gradient during emergence of O. agrili generations. Determining day lengths perceived by O. agrili larvae in the field should improve model realism for examining spatiotemporal variation in O. agrili population dynamics.

Female-Produced Sex Pheromone of Tetrastichus planipennisi, a Parasitoid Introduced for Biological Control of the Invasive Emerald Ash Borer, Agrilus planipennis.

The Asian eulophid wasp Tetrastichus planipennisi is being released in North America as a biocontrol agent for the emerald ash borer (Agrilus planipennis), a very destructive invasive buprestid beetle that is devastating ash trees (Fraxinus spp.). We identified, synthesized, and tested a female-produced sex pheromone for the wasp. The key component eliciting behavioral responses from male wasps in flight tunnel bioassays was identified as (6S,10S)-(2E,4E,8E)-4,6,8,10-tetramethyltrideca-2,4,8-triene. Female specificity was demonstrated by gas chromatographic (GC) comparison of male and female volatile emissions and whole body extracts. The identification was aided by coupled gas chromatography/mass spectrometry analysis, microchemical reactions, NMR, GC analyses with a chiral stationary phase column, and matching GC retention times and mass spectra with those of synthetic standards. The tetramethyl-triene hydrocarbon was synthesized as a mixture of two enantiomeric pairs of diastereomers, and as the pure insect-produced stereoisomer. In flight-tunnel bioassays, males responded to both the natural pheromone and the chiral synthetic material by upwind flight and landing on the source. In contrast, the mixture of four stereoisomers was not attractive, indicating that one or more of the "unnatural" stereoisomers antagonized attraction. Field trials, using yellow pan traps baited with natural pheromone, captured significantly more male wasps than control traps over a four week trial. The identified pheromone could increase the efficiency and specificity of the current detection methods for Tetrastichus planipennisi and aid in the determination of parasitoid establishment at release sites.

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.

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.

Identifying Possible Pheromones of Cerambycid Beetles by Field Testing Known Pheromone Components in Four Widely Separated Regions of the United States.

The pheromone components of many cerambycid beetles appear to be broadly shared among related species, including species native to different regions of the world. This apparent conservation of pheromone structures within the family suggests that field trials of common pheromone components could be used as a means of attracting multiple species, which then could be targeted for full identification of their pheromones. Here, we describe the results of such field trials that were conducted in nine states in the northeastern, midwestern, southern, and western United States. Traps captured 12,742 cerambycid beetles of 153 species and subspecies. Species attracted in significant numbers to a particular treatment (some in multiple regions) included 19 species in the subfamily Cerambycinae, 15 species in the Lamiinae, one species in the Prioninae, and two species in the Spondylidinae. Pheromones or likely pheromones for many of these species, such as 3-hydroxyhexan-2-one and syn- and anti-2,3-hexanediols for cerambycine species, and fuscumol and/or fuscumol acetate for lamiine species, had already been identified. New information about attractants (in most cases likely pheromone components) was found for five cerambycine species (Ancylocera bicolor [Olivier], Elaphidion mucronatum [Say], Knulliana cincta cincta [Drury], Phymatodes aeneus LeConte, and Rusticoclytus annosus emotus [Brown]), and five lamiine species (Ecyrus dasycerus dasycerus [Say], Lepturges symmetricus [Haldeman], Sternidius misellus [LeConte], Styloleptus biustus biustus [LeConte], and Urgleptes signatus [LeConte]). Consistent attraction of some species to the same compounds in independent bioassays demonstrated the utility and reliability of pheromone-based methods for sampling cerambycid populations across broad spatial scales.

Building Double-decker Traps for Early Detection of Emerald Ash Borer.

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire), the most destructive forest insect to have invaded North America, has killed hundreds of millions of forest and landscape ash (Fraxinus spp.) trees. Several artificial trap designs to attract and capture EAB beetles have been developed to detect, delineate, and monitor infestations. Double-decker (DD) traps consist of two corrugated plastic prisms, one green and one purple, attached to a 3 m tall polyvinyl chloride (PVC) pipe supported by a t-post. The green prism at the top of the PVC pipe is baited with cis-3-hexenol, a compound produced by ash foliage. Surfaces of both prisms are coated with sticky insect glue to capture adult EAB beetles. Double-decker traps should be placed near ash trees but in open areas, exposed to sun. Double-decker trap construction and placement are presented here, along with a summary of field experiments demonstrating the efficacy of DD traps in capturing EAB beetles. In a recent study in sites with relatively low EAB densities, double-decker traps captured significantly more EAB than green or purple prism traps or green funnel traps, all of which are designed to be suspended from a branch in the canopy of ash trees. A greater percentage of double decker traps were positive, i.e., captured at least one EAB, than the prism traps or funnel traps that were hung in ash tree canopies.

Optimizing Use of Girdled Ash Trees for Management of Low-Density Emerald Ash Borer (Coleoptera: Buprestidae) Populations.

Effective survey methods to detect and monitor recently established, low-density infestations of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), remain a high priority because they provide land managers and property owners with time to implement tactics to slow emerald ash borer population growth and the progression of ash mortality. We evaluated options for using girdled ash (Fraxinus spp.) trees for emerald ash borer detection and management in a low-density infestation in a forested area with abundant green ash (F. pennsylvanica). Across replicated 4-ha plots, we compared detection efficiency of 4 versus 16 evenly distributed girdled ash trees and between clusters of 3 versus 12 girdled trees. We also examined within-tree larval distribution in 208 girdled and nongirdled trees and assessed adult emerald ash borer emergence from detection trees felled 11 mo after girdling and left on site. Overall, current-year larvae were present in 85-97% of girdled trees and 57-72% of nongirdled trees, and larval density was 2-5 times greater on girdled than nongirdled trees. Low-density emerald ash borer infestations were readily detected with four girdled trees per 4-ha, and 3-tree clusters were as effective as 12-tree clusters. Larval densities were greatest 0.5 ± 0.4 m below the base of the canopy in girdled trees and 1.3 ± 0.7 m above the canopy base in nongirdled trees. Relatively few adult emerald ash borer emerged from trees felled 11 mo after girdling and left on site through the following summer, suggesting removal or destruction of girdled ash trees may be unnecessary. This could potentially reduce survey costs, particularly in forested areas with poor accessibility.

Dilution of Fluon Before Trap Surface Treatment Has No Effect on Longhorned Beetle (Coleoptera: Cerambycidae) Captures.

Several studies have observed that trap captures of longhorned beetles (Coleoptera: Cerambycidae) can be increased by treating the surface of intercept traps with a lubricant. In addition to being expensive, these treatments can alter the spectral properties of intercept traps when applied neat. These surface treatments, particularly Fluon, are commonly used diluted as a low friction coating to prevent insects from climbing out of rearing containers. The purpose of this study was to examine the effect of diluting Fluon on the spectral properties of treated corrugated plastic traps and the capture of longhorned beetles including Monochamus scutellatus (Say), Monochamus mutator (LeConte), and Monochamus notatus (Drury). Intercept panel traps were baited with attractant semiochemicals and treated with either undiluted (i.e., 100%) Fluon, a 1:1 mixture of Fluon and water (50%), a 1:9 mixture of Fluon and water (10%), or untreated. There were no obvious differences in the relative reflectance of untreated black Coroplast plastic or black Coroplast plastic treated with 50 or 10% Fluon. Traps treated with 100% Fluon had similar patterns of peak reflectance to the other treatments but overall had higher relative reflectance. In general, no effect of diluting the Fluon was observed for male or female M. scutellatus or M. mutator , but an effect of treating traps with Fluon was observed. Similar results were observed for the combined captures of Clytus ruricola Olivier, Cyrtophorus verrucosus Olivier, Megacyllene caryae (Gahan), Xylotrechus colonus (F.), Neoclytus acuminatus (F.), Neoclytus mucronatus (F.), and Phymatodes testaceus (L.). No treatment effect was observed for M. notatus .

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.

Lethal trap trees: a potential option for emerald ash borer (Agrilus planipennis Fairmaire) management.

BACKGROUND: Economic and ecological impacts of ash (Fraxinus spp.) mortality resulting from emerald ash borer (EAB) (Agrilus planipennis Fairmaire) invasion are severe in forested, residential and urban areas. Management options include girdling ash trees to attract ovipositing adult beetles and then destroying infested trees before larvae develop or protecting ash with a highly effective, systemic emamectin benzoate insecticide. Injecting this insecticide and then girdling injected trees a few weeks later could effectively create lethal trap trees, similar to a bait-and-kill tactic, if girdling does not interfere with insecticide translocation. We compared EAB larval densities on girdled trees, trees injected with the emamectin benzoate insecticide, trees injected with the insecticide and then girdled 18-21 days later and untreated controls at multiple sites. RESULTS: Pretreatment larval densities did not differ among treatments. Current-year larval densities were higher on girdled and control trees than on any trees treated with insecticide at all sites. Foliar residue analysis and adult EAB bioassays showed that girdling trees after insecticide injections did not reduce insecticide translocation. CONCLUSIONS: Girdling ash trees to attract adult EAB did not reduce efficacy of emamectin benzoate trunk injections applied ≥ 18 days earlier and could potentially be used in integrated management programs to slow EAB population growth.

Abundance of volatile organic compounds in white ash phloem and emerald ash borer larval frass does not attract Tetrastichus planipennisi in a Y-tube olfactometer.

Many natural enemies employ plant- and/or herbivore-derived signals for host/prey location. The larval parasitoid Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is 1 of 3 biocontrol agents currently being released in an effort to control the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coloeptera: Burprestidae) in North America. To enhance its efficiency, allelochemicals that attract it need to be assessed. In this study, ash phloem volatile organic compounds (VOCs) of black, green, and white ash, and EAB larval frass were compared. Foraging behavior of T. planipennisi females in response to VOCs of white ash or frass from EAB larvae feeding on white ash phloem was tested using a Y-tube olfactometer. Results indicated that the 3 ash species had similar VOC profiles. EAB larval frass generally contained greater levels of VOCs than phloem. Factor analysis indicated that the 11 VOCs could be broadly divided into 2 groups, with α-bisabolol, ß-caryophyllene, (E)-2-hexenal, (Z)-3-hexenal, limonene, methyl benzoate, methyl indole-3-acetic acid, methyl jasmonate, methyl salicylate as the first group and the rest (i.e., methyl linoleate and methyl linolenate) as a second. Abundance of VOCs in white ash phloem tissue and frass, nevertheless, did not attract T. planipennisi females. The concealed feeding of EAB larvae might explain the selection for detectable and reliable virbrational signals, instead of undetectable and relatively unreliable VOC cues from phloem and frass, in short-range foraging by T. planipennisi. Alternatively, it is possible that T. planipennisi is not amenable to the Y-tube olfactometer assay employed.

Core RNAi machinery and gene knockdown in the emerald ash borer (Agrilus planipennis).

The RNA interference (RNAi) technology has been widely used in insect functional genomics research and provides an alternative approach for insect pest management. To understand whether the emerald ash borer (Agrilus planipennis), an invasive and destructive coleopteran insect pest of ash tree (Fraxinus spp.), possesses a strong RNAi machinery that is capable of degrading target mRNA as a response to exogenous double-stranded RNA (dsRNA) induction, we identified three RNAi pathway core component genes, Dicer-2, Argonaute-2 and R2D2, from the A. planipennis genome sequence. Characterization of these core components revealed that they contain conserved domains essential for the proteins to function in the RNAi pathway. Phylogenetic analyses showed that they are closely related to homologs derived from other coleopteran species. We also delivered the dsRNA fragment of AplaScrB-2, a ß-fructofuranosidase-encoding gene horizontally acquired by A. planipennis as we reported previously, into A. planipennis adults through microinjection. Quantitative real-time PCR analysis on the dsRNA-treated beetles demonstrated a significantly decreased gene expression level of AplaScrB-2 appearing on day 2 and lasting until at least day 6. This study is the first record of RNAi applied in A. planipennis.

Comparison of trap types and colors for capturing emerald ash borer adults at different population densities.

Results of numerous trials to evaluate artificial trap designs and lures for detection of Agrilus planipennis Fairmaire, the emerald ash borer, have yielded inconsistent results, possibly because of different A. planipennis population densities in the field sites. In 2010 and 2011, we compared 1) green canopy traps, 2) purple canopy traps, 3) green double-decker traps, and 4) purple double-decker traps in sites representing a range of A. planipennis infestation levels. Traps were baited with cis-3-hexenol in both years, plus an 80:20 mixture of Manuka and Phoebe oil (2010) or Manuka oil alone (2011). Condition of trees bearing canopy traps, A. planipennis infestation level of trees in the vicinity of traps, and number of A. planipennis captured per trap differed among sites in both years. Overall in both years, more females, males, and beetles of both sexes were captured on double-decker traps than canopy traps, and more beetles of both sexes (2010) or females (2011) were captured on purple traps than green traps. In 2010, detection rates were higher for purple (100%) and green double-decker traps (100%) than for purple (82%) or green canopy traps (64%) at sites with very low to low A. planipennis infestation levels. Captures of A. planipennis on canopy traps consistently increased with the infestation level of the canopy trap-bearing trees. Differences among trap types were most pronounced at sites with low A. planipennis densities, where more beetles were captured on purple double-decker traps than on green canopy traps in both years.

Trap lure blend of pine volatiles and bark beetle pheromones for Monochamus spp. (Coleoptera: Cerambycidae) in pine forests of Canada and the United States.

In 2007-2008, we examined the flight responses of Monochamus titillator (F.) complex [M. titillator, Monochamus carolinensis (Olivier), and any possible hybrids], Monochamus scutellatus (Say), Monochamus clamator (LeConte), Monochamus obtusus Casey, and Monochamus mutator LeConte (Coleoptera: Cerambycidae) to multiple-funnel traps baited with and without host volatiles and bark beetle pheromones. Experiments were conducted in mature pine (Pinus) stands in Alberta (Canada), and Arkansas, Arizona, California, Florida, Idaho, Michigan, Montana, New Hampshire, North Carolina, Ohio, Oregon, Tennessee, Utah, and Wisconsin (United States). At each location, traps were deployed in 10 replicate blocks of four traps per block. The trap treatments were: 1) blank control; 2) ipsenol and ipsdienol; 3) ethanol and alpha-pinene; and 4) a quaternary blend of ipsenol, ipsdienol, ethanol, and alpha-pinene. All five species or species complex of Monochamus preferred traps baited with the quaternary blend over all other treatments. The consistency of these results across such a large geographic area suggests that similar selection pressures may be acting on Monochamus spp. in pine forests, regardless of variation in stand composition and climatic conditions. Our results suggest that multiple-funnel traps baited with the quaternary blend ofipsenol, ipsdienol, ethanol, and alpha-pinene may be highly effective for monitoring various Monochamus spp. in pine forests of North America, and may have utility in trapping and detection programs in North America and overseas.

Identification of odor-processing genes in the emerald ash borer, Agrilus planipennis.

BACKGROUND: Insects rely on olfaction to locate food, mates, and suitable oviposition sites for successful completion of their life cycle. Agrilus planipennis Fairmaire (emerald ash borer) is a serious invasive insect pest that has killed tens of millions of North American ash (Fraxinus spp) trees and threatens the very existence of the genus Fraxinus. Adult A. planipennis are attracted to host volatiles and conspecifics; however, to date no molecular knowledge exists on olfaction in A. planipennis. Hence, we undertook an antennae-specific transcriptomic study to identify the repertoire of odor processing genes involved in A. planipennis olfaction. METHODOLOGY AND PRINCIPAL FINDINGS: We acquired 139,085 Roche/454 GS FLX transcriptomic reads that were assembled into 30,615 high quality expressed sequence tags (ESTs), including 3,249 isotigs and 27,366 non-isotigs (contigs and singletons). Intriguingly, the majority of the A. planipennis antennal transcripts (59.72%) did not show similarity with sequences deposited in the non-redundant database of GenBank, potentially representing novel genes. Functional annotation and KEGG analysis revealed pathways associated with signaling and detoxification. Several odor processing genes (9 odorant binding proteins, 2 odorant receptors, 1 sensory neuron membrane protein and 134 odorant/xenobiotic degradation enzymes, including cytochrome P450s, glutathione-S-transferases; esterases, etc.) putatively involved in olfaction processes were identified. Quantitative PCR of candidate genes in male and female A. planipennis in different developmental stages revealed developmental- and sex-biased expression patterns. CONCLUSIONS AND SIGNIFICANCE: The antennal ESTs derived from A. planipennis constitute a rich molecular resource for the identification of genes potentially involved in the olfaction process of A. planipennis. These findings should help in understanding the processing of antennally-active compounds (e.g. 7-epi-sesquithujene) previously identified in this serious invasive pest.