Efficacy of semiochemical-baited traps for detection of Scolytinae species (Coleoptera: Curculionidae) in the Russian Far East

Traps baited with plant volatiles and/or bark beetle pheromones have been used to survey for exotic and potentially invasive bark and wood-boring beetles in North America since the mid-1990s. Recent discoveries of sex and aggregation pheromones in the Cerambycidae offer means of improving detection rates of longhorn beetles, but little is known of their effects on detection of bark and ambrosia beetles in the subfamily Scolytinae. Our objectives were to determine the effi cacy of host volatile trap lures for survey and detection of Scolytinae species and whether that effi cacy was affected by the addition of longhorn beetle pheromones. More than 12,000 specimens and 36 species of Scolytinae were collected in two fi eld trapping bioassays conducted in the Russian Far East in 2009 and 2010. The lure combination of spruce blend (a blend of racemic α-pinene, (–) β-pinene, (+)-3-carene, (+)-limonene, and α-terpinolene) and ethanol signifi cantly increased detection rates and mean catches of Hylastes brunneus Erichson, Hylastes obscurus Chapuis, Ips typographus (L.), and Dryocoetes striatus Eggers compared with unbaited traps. The addition of the longhorn beetle pheromones, E-fuscumol, or E-fuscumol acetate, to traps baited with spruce blend and ethanol, slightly reduced mean catches of D. striatus but otherwise did not affect catch of any Scolytine species. Baiting traps with ethanol signifi cantly increased mean catches of Anisandrus apicalis (Blandford), Anisandrus dispar (Fabr.), Anisandrus maiche (Kurenzov), Xyleborinus attenuatus (Blandford), Xyleborinus saxesenii (Ratzeburg), Xylosandrus germanus (Blandford), Scolytoplatypus tycon Blandford, and Trypodendron lineatum (Olivier). By themselves, the longhorn beetle pheromones, racemic hydroxyhexan-2-one and racemic hydroxyoctan-2-one, were not attractive to any Scolytine species. However, when added to ethanol-baited traps, hydroxyhexan-2-one lures signifi cantly increased mean catch of S. tycon, hydroxyoctan-2-one lures signifi cantly reduced mean catches of A. maiche and X. attenuatus, and lures of either hydroxyketone signifi cantly reduced mean catch of T. lineatum. The lure treatments that detected the greatest number of species per sampling effort were spruce blend plus ethanol in 2009 (16 Scolytinae species and 13 species of Cerambycidae combined in an eight-trap sample) and hydroxyhexan-2-one plus ethanol in 2010 (20 Scolytinae species and 7 species of Cerambycidae combined in an eight-trap sample). Species accumulation curves did not reach an asymptote for any lure treatment, indicating that many species would go undetected in samples of 8–9 traps per site.


INTRODUCTION
Species of bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are readily carried in untreated solid-wood packaging used in the shipment of goods internationally and, as such, are frequently intercepted as exotic species in many countries (Haack, 2001(Haack, , 2006;;Brockerhoff et al., 2006).Several of these exotic bark and ambrosia beetles have become established in North America (LaBonte et al., 2005;Haack, 2006;Haack & Rabaglia, 2013), New Zealand (Brockerhoff et al., 2006), and Europe (Kirkendall & Faccoli, 2010), often outnumbering native Scolytinae in trapping surveys (Miller & Rabaglia, 2009;Gandhi et al., 2010), and some species have been particu-host volatiles on detection of Scolytinae.Noseworthy et al. (2012) reported that attraction of Monarthrum scutellare (LeConte) was synergized by the combination of racemic 3-hydroxyoctan-2-one and ethanol.Miller et al. (2015b) found that mean catches of Hypothenemus rotundicollis Wood & Bright and Dryoxylon onoharaensum (Murayama) in ethanol-baited traps increased and decreased, respectively, with the addition of racemic 3-hydroxyoctan-2-one, but that catches of other Scolytinae species were largely unaffected.Knowledge of the effects of such lure combinations on the detection of Cerambycidae and Scolytinae, whether they are positive, negative, or neutral, is necessary to optimize surveillance programs for exotic bark and wood-boring beetles.
The objectives of this study were to determine the relative effi cacy of various combinations of host volatile and longhorn beetle pheromone lures for the survey and detection of Scolytinae species native to the Russian Far East and whether that effi cacy was positively or negatively affected by the addition of longhorn beetle pheromones.This area shares similar climate and genera of trees and bark beetles with parts of northeastern China (= "Manchuria") (Krestov, 2003) as well as northeastern North America and was therefore suitable for comparing the effi cacy of lures for detecting species of Scolytinae that might be inadvertently introduced to North America.We predicted that the longhorn beetle pheromones would likely increase mean catches of some Scolytinae species, but would likely also decrease catches of other species.Data on the mean catch and rate of detection of Cerambycidae species in these experiments were reported earlier (Sweeney et al., 2014).In addition to presenting results on mean catch and detection rate of Scolytinae species, we also incorporate the data on longhorn species collected in the same site-years (Sweeney et al., 2014) to compare lure treatments for the mean combined number of Scolytinae and Cerambycidae species detected per sampling effort.

METHODS
Two fi eld-trapping bioassays were conducted in the Russian Far East, one from 30 May to 8 August 2009 and the other from 23 May to 21 July 2010, to compare a total of eight different semiochemical lure treatments for their effi cacy in detecting species of bark and ambrosia beetles.Unbaited traps were included as controls in both years.The methods were described in Sweeney et al. (2014) and are summarized here for clarity.

Trapping site
Both experiments were conducted in a relatively undisturbed mixed broadleaf-coniferous forest next to the properties of Sergey R. Shestakov, about 5 km south of the village of Anisimovka in Shkotovsky rayon, Primorsky Kray, Russia (43.1268°N, 132.7973°W;450 m;Fig. 1 in Sweeney et al., 2014).

Semiochemicals, lures, and release rates
Racemic (E)-fuscumol (> 99% pure; GC/MS), hereafter referred to as "F", was synthesized at the Atlantic Forestry Centre (AFC) by lithium aluminum hydride reduction of commercially available (E)-geranyl acetone (Aldrich Chemicals, Milwaukee, WI, USA; < 0.5% Z-isomer), and the structure of the secondary alcohol verifi ed by Electrospray Ionization mass spectrum, and (FAO, IPPC 2013) that require treatment and certifi cation of wood packaging material has reduced the percentage of shipments that contain live pests, but the sheer volume of international trade suggests that the continued introduction and establishment of new exotic bark and wood-boring insects is highly likely (Haack et al., 2014).Traps baited with host volatiles such as ethanol and α-pinene, as well as pheromones of Ips spp., have been used for surveillance of exotic bark and wood-boring beetles in the United States and Canada for more than a decade (Rabaglia et al., 2008;Douglas et al., 2013) and have been reasonably successful at detecting exotic Scolytinae (8 among 18 exotic Scolytinae detected in survey traps between 1985 and 2005) but unsuccessful for species in the Cerambycidae or Buprestidae (0 of 7 species combined, for both families) (Haack 2006).Thus, there is room for improvement in trapping programs for surveillance and early detection of exotic bark and wood-boring beetles.
Racemic 3-hydroxyhexan-2-one and 3-hydroxyoctan-2-one (hereafter referred to as K6 and K8, respectively) were purchased commercially (Bedoukian Research Inc., Danbury, CT), verifi ed as 99% pure by GC/MS at AFC, and loaded into release devices at Contech Inc. (Delta, BC).The release devices consisted of a piece of cellulose sponge (7.0 cm × 5.0 cm × 0.5 cm) inside a polyethylene pouch into which 1.4 g of either K6 or K8 was pipetted, and the pouch heat-sealed.The release rates, determined gravimetrically at 20°C, were 20 mg/d and 25 mg/d for K8 and K6, respectively, and these rates remained steady for more than 50 d.For traps baited with either K6 or K8, we placed two pouches per trap to obtain release rates of 40-50 mg/d and did not replace the lures.
Ultra-high release rate lures of spruce blend, also known as brown spruce longhorn beetle kairomone, hereafter referred to as "SB", and ethanol, hereafter referred to as "E", were purchased commercially (Contech Inc, Delta, BC).Release rates of SB (44% racemic α-pinene, 19% (-) β-pinene, 10% (+)-3-carene, 18% (+)-limonene, and 9% α-terpinolene) and E lures were about 2 g/d and 275 mg/d, respectively (Sweeney et al., 2006).Due to diffi culties in shipping and receiving ethanol lures (considered dangerous goods) to Russia in 2010, we purchased empty ethanol release devices from Contech Inc. and fi lled them with locally purchased vodka (40% ethanol), sealing the top of the release device by folding the top of the sleeve over twice and pinching it with a strong paper clamp.This likely reduced the release rates of ethanol in 2010 to about half of that in 2009.The ethanol lures in 2010 may also have emitted trace amounts of compounds such as fusel oils, acetates, and acetic acid, as vodka often contains these impurities at concentrations ranging from 0.001 to 0.3% (Hu & Schaefer, 2010).We acknowledge that response of beetles to these lures may possibly have been affected by one or more of these trace compounds in the vodka but due to their very low concentrations relative to ethanol, we argue that any effects on beetle behavior were probably slight.For traps baited with E or SB, we placed one lure per trap and did not replace the lures.
Experiments were replicated in randomized complete block designs with eight replicates per treatment and 20-30 m spacing between traps and blocks.Black panel intercept traps (Alpha Scents, Inc., Portland OR) (Fig. 1 in Sweeney et al., 2014) were suspended from rope tied between two trees so that the collecting cup was at least 30-60 cm above the ground and the trap was at least 1 m distant from each tree.Collecting cups were partially fi lled with 60% ethylene glycol in water.Traps were emptied every week for a total of 8-10 weeks, and captured insects sealed in Whirlpak bags with 96% ethanol labeled by date, lure treatment, and block, and stored at room temperature until sorting.

Specimen identifi cation, deposit, and taxonomy
All specimens of Scolytinae were identifi ed to species, and pinned voucher specimens were deposited in the Canadian National Collection of Insects, Arachnids and Nematodes in Ottawa.Species' names and classifi cation were adopted following Knížek (2011).

Data analysis
Because lure treatments differed between years, the data were analyzed separately for each experiment.For each species, a replicate was the total number of specimens captured per trap over the entire 8-10 week trapping period.A chi-square goodness-offi t test was used to test whether the number of species detected differed among lure treatments.Cochran's Q test for dichotomous data in randomized blocks (Zar, 1999) was used to test the null hypothesis that the proportion of traps that collected at least one specimen of that species was the same for all lure treatments (α = 0.05), i.e., a signifi cant Q value indicated that lure treatments differed in effi cacy of detection.Cochran's Q was calculated only for species that were detected in at least four (2010 experiment) or fi ve (2009 experiment) different trap blocks, such that the product of "a" (number of lure treatments) × "b" (number of blocks in which the species was detected in some but not all treatments) was 24 or greater (Zar, 1999).For species for which at least ten specimens were captured, data on the number of specimens per trap were fi rst transformed by log(y+1) and then subjected to ANOVA using the model: catch = block + lure treatment + error, using SAS PROC GLM (SAS Institute, 2002-2003).Residuals were checked for normality using Shapiro-Wilks test in SAS PROC Univariate.If residuals of the log-transformed data departed signifi cantly from normality, the raw values were rank transformed and subjected to GLM (Friedman's Test; Zar, 1999).For both log-and rank-transformed data, means were compared using the Ryan-Einot-Gabriel-Welsh multiple comparison test in SAS GLM.
The degree of similarity in species composition among lure treatments was determined by calculating the qualitative Sorensen index, which compares incidence of species, and the quantitative Morasita-Horn index (MH), which compares both incidence and abundance of species; both indices were calculated using EstimateS version 9 (Colwell, 2013).EstimateS was also used to calculate the mean number of species detected per number of trap samples using Coleman's rarefaction.This was done to compare the number of species detected per sampling effort (i.e., number of traps) among each of the different lure treatments.We also used Coleman's rarefaction to estimate the mean number of species detected per sampling effort for all binary combinations of lure treatments in each year, i.e., ten binary combinations of the fi ve different lure treatments in 2009 (e.g., traps baited with K6+E combined with traps baited SB+E) and 15 binary combinations of the six different lure treatments in 2010.In other words, we wanted to see whether detection effi cacy could be improved by using more than one kind of lure treatment at a site, e.g., if traps baited with K6+E attract a different set of species than traps baited with SB+E, then deploying four traps baited with K6+E plus four traps baited with SB+E may detect more species than eight traps baited with either K6+E or SB+E.Coleman's rarefaction does not estimate true species richness but only the aver-age number of species detected per 1, 2….n samples (i.e., trap samples in our case) collected from a given area.In this sense, it provides a measure of how many traps are needed to detect most of the species liable to be detected with a given lure treatment, or conversely, the proportion of species that may go undetected when the number of traps per site is limited.The similarity indices and rarefaction curves were calculated for Scolytinae species, and also for total species of Scolytinae and Cerambycidae combined.The rarefaction curves for Cerambycidae species detected in these trapping experiments were previously reported (Sweeney et al., 2014).

Mean catch per trap
Lure treatment signifi cantly affected mean catch per trap of seven species in 2009 (Fig. 1).The combination of Table 2. Number of bark and ambrosia beetles (Curculionidae) collected in a mixed coniferous-broadleaf forest near Vladivostok, Russia, 23 May-21 July 2010, in black panel intercept traps baited with E (40% ethanol), K6 (racemic 3-hydroxyhexan-2-one), K8 (racemic 3-hydroxyoctan-2-one), K6 + E, K8 + E, or C (unbaited control), in a mixed wood (n = 8 traps per lure treatment).Bold font indicates species for which lure treatments differed signifi cantly in mean catch per trap (ANOVA, α = 0.05) or the proportion of traps that detected at least one specimen (Cochran's Q test, Zar, 1999) and also those lure(s) with the greatest mean catch or rate of detection.

Detection effi cacy
Results in terms of detection rate were similar to those for mean catches in both years, i.e., the proportion of traps that captured at least one specimen differed signifi cantly among treatments for all of the species for which mean  catch differed among treatments, with the exception of S. tycon (Tables 1, 2).Although mean catch of S. tycon was clearly greater in traps baited with K6+E than in most other lure treatments in both years, the species was also present in 50-75% of unbaited traps, albeit in much lower numbers.

Number of Scolytinae species detected per sampling effort
The total number of Scolytinae species detected (per eight replicate traps) varied among lure treatments, from 11 species in traps baited with FA+SB+E to 16 species in traps baited with SB+E in 2009 (Fig. 3a), and from 10 species in traps baited with K6 to 20 species in traps baited with K6+E in 2010 (Fig. 3b, Table 3).The addition of F or FA to traps baited with spruce blend and ethanol reduced the number of Scolytinae species detected per trap (Fig. 3a); in fact, traps baited with F+SB+E or FA+SB+E detected fewer species per trap than did unbaited traps.Conversely, the addition of K6 or K8 to ethanol-baited traps either increased the number of species detected or had little effect (Fig. 3b).However, although the number of specimens detected varied signifi cantly among lure treatments in both 2009 and 2010, the number of species detected did not (Chi square goodness of fi t tests, P < 0.05) (Tables 1, 2).Species composition, as measured by Sorenson's qualitative index, was least similar between traps baited with K6+E and traps baited with SB+E in 2009 and between traps baited with K6 and unbaited traps in 2010 (Table 3).The binary combination of different lure treatments that resulted in the greatest number of Scolytinae species detected (i.e., in a combined total of 16 traps) was the combination of traps baited with K6+E and traps baited with SB+E in 2009 (23 species detected) (Fig. 3c) and traps baited with K6+E plus unbaited traps in 2010 (23 species detected) (Fig. 3d, Table 3).In 2009, the binary treatment combination of traps baited with K6+E plus traps baited with SB+E performed only marginally better than traps baited with the best individual lure treatment combination (SB+E), detecting about 17 species compared with 16 species per eight traps.This was not true in 2010 when the best single lure treatment, K6+E, detected more Scolytinae species per trap than any binary treatment combination (Fig 3b,d).None of the species accumulation curves appeared to reach an asymptote with the exception of perhaps traps baited with FA+SB+E (Fig. 3a) or K6 or K8 alone (Fig. 3b).

Number of combined Scolytinae and Cerambycidae species detected per sampling effort
When data on catch of Cerambycidae species were combined with those for Scolytinae, the relative differences among lure treatments in number of species detected was less than that observed for Scolytinae alone in 2009 (Fig. 4a vs. 3a) and, surprisingly, the performance of K6+E was about that same as ethanol alone in 2010 (Fig. 4 b).The similarities in composition of Scolytinae and Cerambycidae species between different lure treatments were comparable to those for Scolytinae species (Table 4).In 2009, SB+E detected the most species of any lure treatment (29 species per eight traps) and detection effi cacy was improved (to 33 species detected in eight traps) by using a combination of SB+E and K6+E (Fig. 4c).The latter two treatments also had one of the least similar species compositions of any binary treatment combination in 2009 (Table 4).However, in 2010, no combination of two lure treatments increased the number of species detected per trap over that detected with traps baited with the single lure treatment of K6+E (27 species in eight traps) (Fig. 4d).

DISCUSSION
Our results demonstrate the effi cacy of traps baited with ethanol and monoterpenes as survey tools for particular species of Scolytinae native to the Russian Far East, especially those in the tribe Xyleborini, but also suggest that many Scolytinae species may go undetected by such traps or be detected only by chance.A total of 116 species from 35 genera of Scolytinae are recorded from the Primorsk Territory (southernmost continental Province of the Russian Far East) (Krivolutskaja, 1996), and 58 species were collected in extensive surveys in the Lazo Nature Reserve (Mandelshtam & Petrov, 2009), located at the same latitude in Primorsk Territory as the present study site near Anisimovka.Thus, the detection of only 36 species of Scolytinae suggests that our traps and lures failed to detect about half of the species present at the site.
We also demonstrate that the addition of longhorn beetle pheromones to host volatile-baited traps can have both positive and negative effects on detection of Scolytinae species, depending on the pheromone-host volatile combination, and the particular beetle species.
It is not possible to compare the relative performance of our lure treatments for consistency between years because the same set of lure treatments was not tested each year.However, testing a different set of lure treatments in each year allowed us to screen a greater total number of lure treatments for their effi cacy at detecting Scolytinae in the Russian Far East, one of the main goals of this study.Furthermore, the inclusion of unbaited controls in each year provides a common baseline with which to compare lure treatments and for those species for which we infer mean catch was affected by lure treatment, the effect was highly signifi cant (P < 0.0001).Some differences between years were apparent in response to K6+E.Anisandrus apicalis, A. maiche and S. tycon responded positively to traps baited with K6+E in both years, whereas A. dispar, X. germanus, X. attenuatus and X. saxesenii responded positively to K6+E in 2010 only.We can only speculate on possible reasons for these differences: (1) our use of vodka rather than 95% ethanol in 2010 may have affected response of some species, either due to the presence of impurities in the vodka, or to the lower concentration of ethanol (40% vs. 95%), or both; (2) activity level and or population densities of some species may have differed between years due to stochastic factors like weather.
The relatively low ca tches of H. palliatus in traps baited with ethanol or spruce blend plus ethanol were initially surprising because Schroeder (1988) trapped this species in relatively large numbers in Sweden in transparent fl ight barrier traps baited with ethanol or ethanol plus α-pinene, and the fi rst North American record of this species was from a trap baited with ethanol and α-pinene (Rabaglia et al., 2008).Similarly, we collected very few specimens of X. seriatus in our traps even though this species has been collected in the hundreds in funnel traps baited with ethanol plus α-pinene in Massachusetts (Hoebeke & Rabaglia, 2008, http://www.barkbeetles.info/index.php).It is possible that populations of these species were relatively low at our sites, or that attraction to ethanol or ethanol and α-pinene was interrupted by the presence of longhorn beetle pheromones or additional monoterpenes in the spruce blend.However, it is more likely that the lower than ex- pected catches are because we missed the main fl ight periods of these species.Our traps were out between late May and late July -early August; peak fl ights of H. palliatus occurred in late April (overwintered generation) and August (new generation) in Denmark (Subansenee, 1971), and those of X. seriatus occurred in mid-May in Massachusetts.
Lure treatment signifi cantly affected beetle species composition in traps and likely refl ected the volatiles emitted from suitable brood hosts (Schroeder & Lindelöw, 1989;Miller & Rabaglia, 2009;Ranger et al., 2011).Ethanol is found in the bark and sapwood of stressed trees (Kimmerer & Koslowski, 1982), stumps (Kelsey & Joseph, 1999) and logs (Kelsey, 1994), which provide suitable breeding material for many species of bark and ambrosia beetles, and thus likely acts as a host kairomone (Schroeder, 1988;Lindelöw et al., 1993;Raffa et al., 1993).Beetles that responded positively to traps baited with spruce blend plus ethanol, such as Ips typographus and Hylastes spp., likely did so because the lures simulated volatiles emitted from stressed or moribund conifers, preferred hosts of these species (Wood & Bright, 1992;Wermelinger, 2004;Lindgren & Raffa, 2013).The reduced catch of A. dispar, A. maiche, and S. tycon in traps baited with ethanol plus spruce monoterpenes vs. traps baited with ethanol plus racemic 3-hydroxyhexan-2-one was likely because the relatively high release rates of these monoterpenes are probably not typically emitted from suitable hosts; e.g., Anisandrus maiche and A. dispar feed mainly in broadleaf trees (Wood & Bright, 1992).Adding α-pinene to traps baited with ethanol signifi cantly reduced catches of A. dispar, Anisandrus sayi Hopkins, X. saxesenii and Dryoxylon onoharaensis (Murayama) (Schroeder & Lindelöw, 1989;Miller & Rabaglia, 2009;Ranger et al., 2011).Scolytoplatypus tycon is reported from both broadleaf and conifers, including Picea spp.(Wood & Bright, 1992); the negative effect of spruce monoterpenes on attraction of this species to ethanol was possibly due to their ultra-high release rates.Erbilgin et al. (2003) showed that high concentrations of α-pinene inhibited response of Ips pini (Say) to its aggregation pheromone.Our results are similar to those of Miller & Rabaglia (2009) and Ranger et al. (2011) and support their conclusion that detection surveys for bark and ambrosia beetle species should use traps baited with ethanol alone as well as traps baited with ethanol plus α-pinene.
Adding longhorn beetle pheromones to traps baited with ethanol or spruce blend and ethanol had negative, positive, or neutral effects on catch of Scolytinae, depending on the pheromone and beetle species.By itself, neither K6 nor K8 signifi cantly affected trap catch of Scolytinae species.However, the combination of K6+E detected the most species of Scolytinae and Scolytinae plus Cerambycidae of any lure treatment in 2010, suggesting it would increase detection effi cacy compared with traps baited with E alone.Moreover, the addition of K6 to ethanol-baited traps synergized attraction of S. tycon, signifi cantly increasing mean catch twofold and > 100-fold compared with traps baited with ethanol or K6, respectively, but reduced catch of T. lineatum.On the other hand, adding K8 to ethanol-baited traps signifi cantly reduced catches of A. maiche, X. attenuatus, and T. lineatum, and adding either F or FA to traps baited with SB+E caused a slight reduction in catches of D. striatus and reduced the total number of Scolytinae species detected by 4-5 species (25-30%).A negative effect on catch of T. lineatum may actually be a benefi t in terms of processing of catch as this species is Holarctic and thus not a target species in exotic bark and wood-boring beetle surveys traps in North America, but is often captured in large numbers in ethanol-baited traps (Sweeney et al., unpubl. data).The addition of K8 to traps baited with ethanol signifi cantly increased catches of M. scutellare (Noseworthy et al., 2012) and Hypothenemus rotundicollis Wood & Bright (Miller et al., 2015b) and reduced catches of Dryoxylon onoharaensum (Murayama) (Miller et al., 2015b).Positive response of S. tycon to a pheromone that is emitted by many species of longhorn beetles in the subfamily Cerambycinae suggests that S. tycon perceives it as a kairomone indicative of a suitable host for colonization.Many species of Cerambycidae infest stressed or moribund hosts (Linsley, 1961;Solomon, 1995;Hanks, 1999) like those colonized by many species of bark and ambrosia beetles (Furniss & Carolin, 1980).The negative responses of A. maiche, X. attenuatus and T. lineatum to the combination of K8+E suggest it is perceived as an unsuitable host cue, perhaps indicating a host already occupied by longhorn beetles that could compete for space or resources.Overall, our results suggest that combining K6 and E on a single trap increased the number of species of Scolytinae and Cerambycidae detected, thereby reducing costs without signifi cantly reducing detection effi cacy.In a study comparing various trap and lure combinations in Italian ports and surrounding areas, Rassati et al. (2014) similarly found that traps baited with multi-lure combinations were more effi cient at detecting species of bark and wood-boring beetles than were traps baited with single lures.However, our study also shows that some multiple lure combinations (e.g., K8+E) reduce the attraction of certain species, e.g., A. maiche, X. attenuatus, and T. lineatum.Thus, knowledge of how different target species respond to different lure combinations must be taken into consideration when designing operational surveys.It was also apparent from our data that many of the Scolytinae species that we detected were not signifi cantly attracted to any of the lure treatments in 2009 (20/27 species) or 2010 (20/28 species).Furthermore, as pointed out by Miller et al. (2015b), although we can compare the relative effi cacy of traps and lures for detection of a given species, we do not have independent data on population densities of any species at our experimental sites.Thus we do not know the relationship between mean catch and population density for any species and, therefore, have no measure of how sensitive a trap-lure is in terms of detecting a low density population of an exotic beetle that may recently have established in a new range.Future research should address this question, especially for high risk target species.