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Nationwide survey for invasive wood-boring and bark beetles (Coleoptera) using traps baited with pheromones and kairomones
Forest Ecology and Management 228 (2006) 234–240 www.elsevier.com/locate/foreco
Nationwide survey for invasive wood-boring and bark beetles (Coleoptera) using traps baited with pheromones and kairomones Eckehard G. Brockerhoff a,*, Diane C. Jones b, Mark O. Kimberley b, D. Max Suckling c, Terry Donaldson d a
Ensis,1 P.O. Box 29237, Fendalton, Christchurch, New Zealand b Ensis,1 Private Bag 3020, Rotorua, New Zealand c HortResearch, P.O. Box 51, Lincoln, New Zealand d AgriQuality, Private Bag 4718, Christchurch, New Zealand
Received 6 August 2005; received in revised form 20 February 2006; accepted 20 February 2006
Abstract Exotic wood borers and bark beetles (WBBB) pose a considerable threat to trees and forests, and the challenge of timely detection and response is significant. The Ministry of Agriculture and Forestry implemented a national surveillance programme for invasive WBBB targeted at species that could become serious pests of New Zealand’s large conifer plantations and unique native forests. The three aims for 2002–2005 were for the programme to act as an early-warning system to detect newly established beetles, to test the efficacy of different lures for established or newly established exotic species and to study the effects of trap placement and proximity of host trees on trap catch in order to improve trap efficiency. For the general surveillance programme, up to 580 funnel traps baited with either a-pinene and ethanol, b-pinene and ethanol, frontalin and ethanol or ipsdienol were placed around New Zealand at high-risk sites including all major seaports, international airports, devanning sites and also in forests near high-risk sites. Additional traps were used to compare these lures with unbaited control traps to assess their effectiveness in catching established exotic WBBB, and to assess the effects of placing traps at varying distances from host trees. Over 27,000 beetles were caught during the general survey from 2002 to 2004, and no new establishments were detected. Between 51% and 88% of all catches were of Scolytinae or Cerambycidae, and most of these were accounted for by the three exotic species Arhopalus ferus, Hylurgus ligniperda and Hylastes ater. Overall, these three species were most attracted to traps baited with a-pinene and ethanol. Catches ‘near’ and ‘far’ from trees differed little for A. ferus and H. ater. H. ligniperda were caught in significantly lower numbers near trees. The results confirm that a trapping programme like the one described here is likely to assist with the early detection of any new establishments, which would improve the chances of successful eradication. # 2006 Elsevier B.V. All rights reserved. Keywords: Exotic species; a-Pinene; b-Pinene; Scolytidae; Cerambycidae
1. Introduction Wood boring and bark beetles are among the most significant forest pests worldwide (Rudinsky, 1962; Wood, 1982a; Gordh and Headrick, 2001). With numerous invasive species, such beetles represent an important threat to the biosecurity of all forested countries (Liebhold et al., 1995; Paine et al., 1997; Haack, 2001; Nowak et al., 2001; Brockerhoff et al., 2006). The most important taxa among invasive wood boring and bark
* Corresponding author Tel.: +64 3 3642949; fax: +64 3 3642812. E-mail address: [email protected] (E.G. Brockerhoff). 1 Ensis is a joint venture between CSIRO and SCION/New Zealand Forest Research Institute Ltd. 0378-1127/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2006.02.046
beetles (WBBB) are bark and ambrosia beetles (Curculionidae: Scolytinae), longhorn beetles (Cerambycidae), and to a lesser extent, other Curculionidae, jewel beetles (Buprestidae), and several other families. For example, 50 exotic Scolytinae are established in the continental U.S. and Canada (Haack, 2001) while New Zealand has 11 exotic Scolytinae (Brockerhoff et al., 2003). Despite a raised international awareness of threats from invasive species, growing international trade and tourism are likely to have caused increasing arrival rates of exotic organisms. High-risk pathways such as air cargo, containers and refrigerated shipments are becoming more common, further enhancing the risk of importing new pests (Dobbs and Brodel, 2004; Work et al., 2005). Forests are an important habitat for much of New Zealand’s unique biodiversity, which includes many threatened, endemic
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species. In addition to the remaining natural forests which cover about 20% of the land, there are over 1.8 million ha of plantation forests that meet most of the country’s wood product needs and also supply forest products for one of the largest export sectors. It is widely recognised that both plantations and natural forests are at risk from invasive species (e.g., Ohmart, 1982; Atkinson and Cameron, 1993). Early detection of new establishments is critical for the most effective implementation of management and eradication efforts (Myers et al., 2000). Consequently, many countries maintain surveillance programmes that involve inspection of forests and trees (e.g., Carter, 1989). An alternative surveillance approach relies on the fact that many WBBB are attracted to host volatiles (e.g., Schroeder and Lindelo¨w, 1989), and sex or aggregation pheromones (Wood, 1982b). The New Zealand Ministry of Agriculture and Forestry (MAF) implemented a nationwide survey for invasive WBBB using funnel traps baited with several attractants that are suitable for a range of high-risk Scolytinae, Cerambycidae and other beetles from important pest genera such as Dendroctonus, Ips and Monochamus. Traps were set up at high-risk sites such as seaports, airports, devanning (container unloading) sites and in forests near highrisk sites. The trapping programme reported here took place from 2002 to 2005 and addressed the following objectives: (1) to act as an early-warning system to detect newly established WBBB, (2) to test the efficacy of species-specific and general lures for exotic WBBB, including species that have become established previously and (3) to study the effects of trap placement, with regard to proximity of host trees. The latter point was addressed to reduce uncertainty about the efficacy of traps placed near host trees because of the potential competition from attractants (i.e., volatiles) emanating from trees. 2. Methods
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Fig. 1. Map of trapping locations and mean catches per trap in 2002–2003 of the three most abundant exotic wood borers and bark beetles, Hylastes ater, Hylurgus ligniperda and Arhopalus ferus. Asterisks show two additional locations where trapping took place in 2003–2004 (catch data for 2003– 2004 are not shown).
throughout New Zealand (Fig. 1) at high-risk sites including all major seaports, international airports, devanning sites where containers are unloaded, and, in 2003–2004, also in forests near high-risk sites. To avoid vandalism, wherever possible, traps were set in secure areas with no public access. Most traps were suspended from steel posts except where other suitable structures, such as wire fences, existed. All traps were set at a height of about 2 m. Trapping took place from October to May (i.e., over the southern hemisphere summer). Traps were checked about every 14 days and samples were sent to Forest Research for identification using standard literature (Klimaszewski and Watt, 1997; and references therein) and reference material in the Forest Research/Ensis Insect Collection.
2.1. Trapping design, lures and study sites 2.2. General survey Trap placement and other specifications were in accordance with the ‘Standard, Specification for Surveillance of Wood Boring and Bark Beetles, New Zealand Ministry of Agriculture and Forestry – Biosecurity Authority, Forest Biosecurity’ (Ministry of Agriculture and Forestry, 2003; and earlier versions), which had been developed with advice from scientists specialising in this field. Eight-unit Lindgren-type funnel traps (PheroTech, Delta, BC, Canada) were used for this study. Lures included general attractants for bark beetles and wood borers as well as two bark beetle pheromones: (1 and 3) a-pinene (95% minus enantiomer, release rate ca. 2 g per day at 20 8C) plus ethanol (release rate ca. 30 mg per day at 20 8C), (2) frontalin (ca. 2.3 mg per day at 20 8C) plus ethanol (as above), (4) ipsdienol (racemic, ca. 0.2 mg per day at 25 8C), (5) bpinene (predominantly minus enantiomer, ca. 100 mg per day at 20 8C) plus ethanol, (6) control (blank). All lures and lure specifications were obtained from PheroTech. Lures were stored in a freezer until used and replaced every 8 weeks (ipsdienol) or 14 weeks (all other lures). Traps were located
In 2002–2003, traps were placed in clusters of four with one each of lures 1–4 (above) at each site. In that year, MAF specified trap positioning in close proximity to high-risk areas but away from standing trees because their presence was thought to reduce trap efficacy. Hence, the trapping protocol was suitable for both established populations as well as for the interception of beetles coming directly from imported freight. A total of 292 traps at 73 site clusters were used from October 2002 to May 2003. Traps were checked about every 2 weeks each giving a total of about 4380 trap readings. In 2003–2004, b-pinene was added because it was found to be particularly attractive to Dendroctonus valens in California (PheroTech red turpentine beetle information sheet). This North American species is of concern because it has become established in China where it is now a significant pest of pine trees. Thus clusters included one each of lures 1–5 (above). A total of 580 traps at 116 site clusters were used for the general survey from December 2003 to May 2004 with 12 trapping
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periods (a total of about 6960 trap readings). The trap placement rules for the general survey were changed to emphasise the detection of established populations, which are most likely to have colonised trees or forests near high-risk sites. Accordingly, in the absence of specific information on optimal trap placement, MAF specified to place traps near potential host trees. 2.3. Effects of trap placement near host trees and comparison of lures with unbaited traps It was unclear whether the placement of traps near trees reduced their efficiency in catching beetles because of the competing attraction of the adjacent host trees, and whether this could compromise the sensitivity of the trapping programme. Therefore, in 2003–2004 additional sets of traps were placed either adjacent to host trees or away from trees. This was done at several sites around Nelson where in previous years catches of the three most common exotic WBBB that are established in New Zealand (Arhopalus ferus Mulsant, Hylastes ater (Paykull) and Hylurgus ligniperda (F.)) have generally been the highest of any location monitored. These additional sets of traps included an unbaited trap (treatment 6 above) to enable a comparison of the effectiveness of the different lures in catching these key WBBB. A total of 80 funnel traps were used to study this aspect. At each of eight replicate sites, five traps, one for each treatment, were placed ‘near’ trees, and five matching traps were placed about 20 m away from trees. Where possible, ‘near’ traps of the on-going 2003–2004 surveillance programme in the Nelson area were used, if these were in fact near trees and if suitable trap locations away from trees existed nearby. This was the case at the Atawhai, Nelson Airport and Rabbit Island (1) sites. Other study sites were added including two additional complete replicates at Rabbit Island (2, 3) and three replicates at Waiwhero Forest west of Nelson. Trapping for this part of the study was carried out during March and April 2004. Additional trapping for A. ferus was undertaken in 2004– 2005 to increase the number of specimens on which the lure comparison was based. Five replicates of lures were used in Eyrewell Forest, Canterbury, from 12 January to 10 February 2005, and another five replicates at Te Puke, Bay of Plenty, from 17 February to 24 March 2005. 2.4. Data analysis Data for the three common introduced species (A. ferus, H. ater and H. ligniperda) were analysed by fitting a log-linear model (McCullagh and Nelder, 1983) for each species. The models contained terms for the site, lure type, and, where applicable, distance from trees (‘near’ and ‘far’). Interactions between these factors were also included in the models. For A. ferus, lure type was analysed with a similar one-way design to accommodate additional data collected in 2004–2005. Models were fitted using the SAS procedure GENMOD (SAS, 2000), with a Poisson error function and the dispersion parameter set to the mean deviance (analysis of deviance or ‘ANODEV’).
Where there were no recorded counts of a species for any lure at a site, that site was dropped from the analysis. Pairwise comparisons were done with LSD tests using log-linear models. To avoid problems with a potentially inflated error rate of multiple comparison tests (Reeve and Strom, 2004), we have used a conservative, Bonferroni-corrected alpha of 0.0167 (0.05/3). Means shown throughout are back-transformed. The Shannon–Wiener diversity index was calculated for species of Scolytinae, Cerambycidae and Platypodinae caught during the regular surveys. 3. Results 3.1. General survey During this survey, at least 82 species of wood boring and bark beetles were trapped, along with many other beetles and other insect orders, which are not addressed further in this paper. The total number of beetles caught was about 19,380 in 2002–2003 and 7967 in 2003–2004. Together, Scolytinae and Cerambycidae accounted for 88% and 51% of catches in the 2 years, respectively (Table 1). One platypodine, the indigenous Platypus apicalis White, was caught (Table 1). Other WBBB (not listed) were mostly from beetle families that infest dead wood, such as Anobiidae and Lyctidae, comprising both indigenous and adventive species. No Buprestidae were caught. The vast majority of these beetles were introduced species. Overall, 99.8% of Scolytinae and 96.3% of Cerambycidae were exotics (Table 1). However, all of these exotic species were known to be established in New Zealand, i.e. no newly established species were detected. The majority of these exotic WBBB are accounted for by just three species, the highly abundant A. ferus (87–99% of the total cerambycid catches in 2002–2003 and 2003–2004), H. ligniperda (54–66% of scolytines) and H. ater (33–35% of scolytines) (Table 1). The dominance of these three species was reflected in the relatively low values of the Shannon–Wiener Index (calculated for Cerambycidae, Scolytinae and Platypodinae) of 1.13 in 2002–2003 and 1.63 in 2003–2004. The three main species, A. ferus, H. ater and H. ligniperda, were present throughout the country but their abundance varied considerably among locations (ANODEV, P < 0.0001) (Fig. 1). H. ater was particularly abundant around Nelson and Invercargill. A. ferus was the most abundant species in the North Island but it was less common in the South Island, except for the Nelson sites where it was particularly abundant. H. ligniperda was very common in the Nelson region, and it was generally more abundant than H. ater except for the far south. There was also considerable variation in catches within a region. For example, in the Nelson region, differences in trap catch among sites were significant for all three species (ANODEV, P < 0.0001 in all cases). A. ferus was most abundant at a fire wood yard at Nelson airport. H. ater occurred at all of the eight Nelson sites and catches differed less among sites than for other species. H. ligniperda was not abundant at Atawhai and Nelson airport but many were caught at both of the plantation forest sites, Rabbit Island and Waiwhero.
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Table 1 Wood boring and bark beetles (Cerambycidae, Scolytinae and Platypodinae) trapped during a New Zealand wide survey Species
Family
Total specimens trapped 2002–2003
Total specimens trapped 2003–2004
Arhopalus ferus (Mulsant)a Hylurgus ligniperda (F.)a Hylastes ater (Paykull)a Xyleborinus saxesenii (Ratzeburg)a Phloeosinus cupressi Hopkinsa Xylotoles griseus (F.) Amasa truncata (Erichson)a Prionoplus reticularis White Calliprason pallidus (Pascoe) Oemona hirta (F.) Bethelium signiferum (Newman)a Platypus apicalis White Hybolasius spp. Pachycotes peregrinus (Chapius) Xylotoles gratus Broun Zorion minutum (F.) Coptodryas eucalyptica (Schedl)a Xylotoles laetus White Callidiopsis scutellaris (F.)a Chaetoptelius mundulus (Broun) Stenopotes spp. Xylotoles humeratus Bates Ambrosiodmus compressusa (Lea) Navomorpha lineata (F.) Ambeodontus tristis (F.) Drototelus elegans (Brookes) Tetrotea spp. Scolytus multistriatus Marshama Leptachrous strigipennis Westwood Hypocryphalus spp. Somatidia spp. Tetrorea sellata Sharp Astetholea lepturoides Bates Coptomma variegatum (F.) Cryphalus wapleri Eichhoffa Metablax cinctiger (White) Xylotoles sp.
Cerambycidae Scolytinae Scolytinae Scolytinae Scolytinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Platypodinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Scolytinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae
7525 6124 3110 9 28 29 51 36 3 16 15 19 1 1 0 3 0 0 7 3 0 0 5 0 1 0 0 2 1 1 0 0 1 1 1 0 0
1768 1082 699 128 74 68 11 17 48 30 27 15 24 15 14 7 10 9 0 3 6 6 0 5 4 3 3 0 1 1 2 2 0 0 0 1 1
Total Scolytinae
9335 (48.2%)
2023 (25.4%)
Total Cerambycidae
7639 (39.4%)
2046 (25.7%)
Total Platypodinae
19 (0.1%)
15 (0.2%)
2387 (12.3%)
3883 (48.7%)
All other Coleoptera a
Exotic species.
3.2. Lure type The lure type used had highly significant effects on trap catch in all three main species (ANODEV, P < 0.001). aPinene plus ethanol and b-pinene plus ethanol were the most attractive lures for A. ferus (Table 2; Fig. 2). It is also noteworthy that non-chemical cues or random trap encounters are important in this species as indicated by catches of the control trap (Fig. 2). There were conflicting results for H. ater because in 2002–2003 most beetles were caught to frontalin plus ethanol and ipsdienol whereas in 2003–2004, the most catches were made to a-pinene plus ethanol and to b-pinene plus ethanol (Table 2; Fig. 3). It is possible that confounding factors relating to trap placement (see below) explain the high
catches to frontalin and ipsdienol, and overall, a-pinene plus ethanol is probably the best lure for this species. The lack of any noticeable differences (in 2003–2004) among catches to frontalin plus ethanol, ipsdienol and the control suggest that these lures are not adding any attraction over the purely visual cues of the funnel trap. Black funnel traps are thought to mimic the visual cues presented by the dark silhouettes of tree boles that contribute to the attraction of bark beetles (e.g., Goyer et al., 2004). H. ligniperda was clearly most attracted by apinene plus ethanol, as shown consistently in all three trials (Table 2; Fig. 4). Catches to b-pinene plus ethanol and ipsdienol were only marginally but still significantly better than the control (Fig. 4). Catches to the control were very small suggesting that visual cues of the funnel traps alone are not
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Table 2 Mean catches per trap during general surveys in 2002–2003 and 2003–2004 of the most abundant wood boring and bark beetle species Lure
Arhopalus ferus
Hylastes ater
Hylurgus ligniperda
2002–2003 a-Pinene + ethanol Frontalin + ethanol Ipsdienol
26.9 (1.7)a 16.3 (1.0)b 18.4 (1.2)b
4.4 (0.5)b 6.8 (0.7)a 8.6 (0.9)a
24.2 (2.5)a 18.3 (1.9)b 9.7 (1.0)c
2003–2004 a-Pinene + ethanol Frontalin + ethanol Ipsdienol b-Pinene + ethanol
7.1 3.5 3.3 11.6
4.9 1.5 0.7 1.9
(1.6)ab (0.8)bc* (0.7)c (2.6)a*
(0.3)a (0.4)b (0.2)b (0.5)b
8.5 1.5 2.1 2.1
(1.5)a (0.3)b (0.4)b (0.4)b
Lindgren traps were baited with one of four different lures. Values in a column followed by the same letter do not differ significantly (a = 0.0167) within a year according to pairwise comparison analyses (LSD) performed using log-linear models. * These treatments differed from a-pinene + ethanol at P = 0.020–0.025.
Fig. 2. Mean trap catch of Arhopalus ferus to different lures in 2003–2004 and 2004–2005 (n = 225 beetles, 21 sites with catches excluding 5 sites with no trapped beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 14.1, F = 8.1, P < 0.0001).
important in this species. Although results from 2002 to 2003 (Table 2) suggest that frontalin plus ethanol is attractive, this was probably either due to the ethanol content or a trap placement artefact (see below).
Fig. 4. Mean trap catch of Hylurgus ligniperda to different lures in 2003–2004 (n = 3316 beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 1464, F = 519.7, P < 0.0001).
3.3. Effect of trap placement near host trees The total catches over the 6-week trapping period in this trial were 3957 individuals of the three species (A. ferus, H. ater and H. ligniperda) targeted for this aspect of the study. Catches of H. ater ‘near’ and ‘far’ from trees differed little (Table 3; ANODEV, mean deviance = 1.6, F = 0.5, P = 0.484). Differences due to distance from trees were significant for A. ferus although the effect size was small (Table 3; ANODEV, mean deviance = 4.5, F = 4.5, P = 0.027). The difference was considerable for H. ligniperda (Table 3; ANODEV, mean deviance = 995.7, F = 353.3, P < 0.0001) but this was mostly due to the very large catch of one trap (with 1403 beetles) out of the eight ‘far’ traps, which was paired with a ‘near’ trap with a moderate catch of 41 beetles. Furthermore, this ‘near’ trap was located near a large kanuka (Kunzea ericoides) tree, which appears to have obscured (chemically and/or visually) this trap to some degree. When this pair is excluded, then the overall difference between ‘near’ and ‘far’ is much smaller (i.e., less than 50% difference). It is also of interest that the type of land or habitat ‘far’ from trees has a considerable influence on the size and ‘direction’ of the effect. At the Atawhai site ‘far’ traps set up in a pasture block caught fewer beetles (only four individuals of the three main species) than the ‘near’ traps set up in an adjacent pine stand (which caught 28 beetles). This contrasts with the overall result of somewhat greater catches ‘far’ from trees, which reflects the situation of ‘far’ sites that had abundant woody debris and associated WBBB. Presumably this contrasting effect of the ‘near/far’ habitat is the reason for the significant Table 3 Mean catch of three beetle species in paired traps located ‘near’ or ‘far’ from trees
Fig. 3. Mean trap catch of Hylastes ater to different lures in 2003–2004 (n = 574 beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 56.6, F = 18.11, P < 0.0001).
Distance from trees
Arhopalus ferus
Hylastes ater
Hylurgus ligniperda
Near (<3 m) Far (20 m)
0.38 (0.07)ba 0.65 (0.12)a
4.27 (0.62)a 4.75 (0.69)a
2.16 (0.29)b 7.12 (0.96)a
Values in a column followed by the same letter do not differ significantly (a = 0.05) according to analysis of deviance using log-linear models.
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distance site interaction of the ANODEV for H. ligniperda (mean deviance = 139.3, F = 49.45, P < 0.0001).
4. Discussion The results of this study confirm that odourant-baited traps can be used effectively for a nationwide surveillance programme to monitor populations of exotic beetles, as well as native species, that infest the wood and bark of trees. Host plant volatiles, particularly a-pinene plus ethanol, proved to be suitable lures for beetles associated with conifers. The attraction of secondary bark beetles of conifers to host odours, particularly to a-pinene alone or in combination with ethanol, is well documented. For H. ater and H. ligniperda, this was shown by Perttunen (1957) and Petrice et al. (2004), respectively. Interestingly, many beetles were caught using unbaited funnel traps, which indicates that visual cues (traps mimics tree trunks) and random trap encounters are also involved. The more species-specific beetle pheromones did not consistently improve catches over unbaited traps for any of the species of which substantial numbers were trapped. This also agrees with previous studies of the secondary species we encountered (e.g., Petrice et al., 2004). However, had there been new establishments of any bark beetle species attracted to the pheromones we tested here, these lures probably would have been more effective than the host plant volatiles. The pheromones chosen are used by many of the most notorious conifer pests from the genera Ips, Dendroctonus and Monochamus (El-Sayed, 2005) and hence their use in a trapping programme to detect new establishments is warranted. Where specific pheromones or other attractants are known for new incursions of exotic species, the best approach is likely to be based on such specific attractants. An example of a bark beetle for which a pheromone is available, and which is of particular relevance to trees in New Zealand, is the smaller elm bark beetle (Scolytus multistriatus (Marsham)). Its pheromone is currently used for surveys in Auckland, New Zealand. In other cases, long range attractants may not be known, for example for the Asian longhorn beetle (Anoplophora glabripennis), and surveys are more cumbersome because they must rely on evidence of tree damage for detection and delimitation. Differences among the relative catches to the different lures used are probably related to: (i) stochastic trapping events that are likely to be most apparent when samples are small, and (ii) trap placement effects. Some of the traps used in port environs in 2002–2003 were positioned near solid fences, walls, or even inside a warehouse. Although it was not possible to retrospectively analyse the degree to which traps positioned in this way influenced the comparison among lures, it can be expected that such traps were less effective at disseminating pheromone and probably less accessible than traps placed in an open area. Such problems were avoided during 2003–2004, and in that year the results were more consistent with other studies. The reason for the greater overall catches in 2002–2003 than in 2003–2004 are probably due to the traps having been placed in
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open, semi-industrial yards where logs and wood were often present versus near trees and other vegetation, respectively. The results of the trial with paired traps positioned near trees and far from trees suggests that this has some, relatively small effect. The major driver for the overall greater ‘far’ catch probably reflects the situation in clearfelled areas (which applied to five of the eight sites) where the abundance of woody debris provided numerous breeding sites and, ultimately, large bark beetle populations. Taken together, the results give no indication that traps placed near host trees (pines in the present study) are much less effective than those about 20 m away. However, it would be of interest to conduct a similar study with traps also placed at greater distances from trees (e.g., 100 m). Overall, the results indicate that a trapping programme for WBBB with traps being placed near trees are likely to yield fewer individuals but more species than when traps are placed in tree-less areas, but there was no clear indication of major negative interference from host trees. A remarkable result was the large number of exotic species that were trapped, their high proportion among the overall catch (over 96% of Scolytinae and Cerambycidae specimens were from exotic species), and the clear dominance of just three species. This reflects the relatively low number of exotic WBBB present in New Zealand (e.g., Brockerhoff et al., 2003), which is probably a result of the geographic isolation of the country and a relatively successful quarantine programme. It also reflects the fact that the attractants used are typically associated with conifer-infesting beetles and conifers, in particular Pinaceae, which are not present in the New Zealand flora, except as introduced trees in plantation forests, shelter belts, and as amenity trees. a-Pinene is mainly attractive to beetles infesting conifers where this monoterpene is common whereas it can be repellent to beetles attacking broadleaved trees (see Schroeder and Lindelo¨w, 1989), which do not usually contain a-pinene. Given the significance of the threat posed by exotic WBBB and their associated pathogens to the plantations of exotic conifers, amenity trees and, for some, also to New Zealand’s native forests, it is critical to remain vigilant and to avoid the establishment of any additional such species. Although relatively expensive, a trapping programme like the one described here is likely to assist with the early detection of any new establishments, which would improve the chances of successful eradication. Acknowledgements We would like to thank Davor Bejakovich and Brendan Murphy (Ministry of Agriculture and Forestry – Biosecurity NZ) for assistance with the co-ordination of the study, Robert Rabaglia (Maryland Dept. of Agriculture) for advice on WBBB trapping designs, the staff of AgriQuality New Zealand for conducting the nationwide survey, Nadine Fletcher, David Logan, Vanessa Mitchell, Peter Shaw, Paula Thomson, and Roger Wallis (HortResearch) for field assistance, and John Bain (Ensis) for assistance with insect identification. Thanks also to John Bain, Brendan Murphy, Mark Ross (Ministry
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of Agriculture and Forestry – Biosecurity NZ), and Andrea Stephens (HortResearch) for reviewing the manuscript. Funding from the Ministry of Agriculture and Forestry and the New Zealand Foundation for Research, Science and Technology (under contract C04X0302) is gratefully acknowledged. References Atkinson, I.A.E., Cameron, E.K., 1993. Human influence on the terrestrial biota and biotic communities of New Zealand. Trends Ecol. Evol. 8, 447–451. Brockerhoff, E.G., Knı´zˇek, M., Bain, J., 2003. Checklist of indigenous and adventive bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) of New Zealand and interceptions of exotic species (1952– 2000). N.Z. Entomol. 26, 29–44. Brockerhoff, E.G., Bain, J., Kimberley, M., Knı´zˇek, M., 2006. Interception frequency of exotic bark and ambrosia beetles (Coleoptera: Scolytinae) and relationship with establishment in New Zealand and worldwide. Can. J. For. Res. 36, 289–298. Carter, P.C.S., 1989. Risk assessment and pest detection surveys for exotic pests and diseases which threaten commercial forestry in New Zealand. N.Z. J. For. Sci. 19, 353–374. Dobbs, T.T., Brodel, C.F., 2004. Cargo aircraft as a pathway for the entry of nonindigenous pests into South Florida. Florida Entomol. 87, 65–78. El-Sayed, A.M., 2005. The Pherobase: Database of Insect Pheromones and Semiochemicals.. Gordh, G., Headrick, D.H., 2001. A Dictionary of Entomology. CAB International, UK, 1032 pp. Goyer, R.A., Lenhard, G.J., Strom, B.L., 2004. The influence of silhouette color and orientation on arrival and emergence of Ips pine engravers and their predators in loblolly pine. For. Ecol. Manage. 191, 147–155. Haack, R.A., 2001. Intercepted Scolytidae (Coleoptera) at U.S. ports of entry: 1985–2000. Integr. Pest Manage. Rev. 6, 253–282. Klimaszewski, J., Watt, J.C., 1997. Coleoptera: family group review and keys to identification. Fauna N.Z. (37), 1–199. Liebhold, A.M., MacDonald, W.L., Bergdahl, D., Mastro, V.C., 1995. Invasion by exotic forest pests: a threat to forest ecosystems. For. Sci. Monogr. 30, 1–49. McCullagh, P., Nelder, J.A., 1983. Generalized Linear Models, first ed. Chapman and Hall, London.
Ministry of Agriculture and Forestry, 2003. Standard, specification for surveillance for wood boring and bark beetles (Coleoptera: Buprestidae, Cerambycidae, Curculionidae, Scolytidae). New Zealand Ministry of Agriculture and Forestry – Biosecurity Authority, Forest Biosecurity, Wellington, New Zealand. Myers, J.H., Simberloff, D., Kuris, A.M., Carey, J.R., 2000. Eradication revisited: dealing with exotic species. Trends Ecol. Evol. 15, 316–320. Nowak, D.J., Pasek, J.E., Sequeira, R.A., Crane, D.E., Mastro, V.C., 2001. Potential effect of Anoplophora glabripennis (Coleoptera: Cerambycidae) on urban trees in the United States. J. Econ. Entomol. 94, 116–122. Ohmart, C.P., 1982. Destructive insects of native and planted Pinus radiata in California, and their relevance to Australian forestry. Aust. For. Res. 12, 151–161. Paine, T.D., Raffa, K.F., Harrington, T.C., 1997. Interactions among scolytid bark beetles, their associated fungi, and live host conifers. Annu. Rev. Entomol. 42, 179–206. Perttunen, V., 1957. Reactions of two bark beetle species, Hylurgops palliatus Gyll. and Hylastes ater Payk. (Col., Scolytidae) to the terpene alpha-pinene. Ann. Entomol. Fenn. 23, 101–110. Petrice, T.R., Haack, R.A., Poland, T.M., 2004. Evaluation of three trap types and five lures for monitoring Hylurgus ligniperda (Coleoptera: Scolytidae) and other local scolytids in New York. Great Lakes Entomol. 37, 1–9. Reeve, J.D., Strom, B.L., 2004. Statistical problems encountered in trapping studies of scolytids and associated insects. J. Chem. Ecol. 30, 1575– 1590. Rudinsky, J.A., 1962. Ecology of Scolytidae. Annu. Rev. Entomol. 7, 327–348. SAS Institute Inc., 2000. SAS/STAT User’s Guide, Version 8, vols. 1–3, SAS Institute Inc., Cary, NC. ˚ ., 1989. Attraction of scolytids and associated Schroeder, L.M., Lindelo¨w, A beetles by different absolute amounts and proportions of a-pinene and ethanol. J. Chem. Ecol. 15, 807–817. Wood, S.L., 1982a. The bark and ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a taxonomic monograph. Great Basin Nat. Mem. 6, 1–1359. Wood, D.L., 1982b. The role of pheromones, kairomones, and allomones in the host selection and colonization behaviour of bark beetles. Annu. Rev. Entomol. 27, 411–446. Work, T.T., McCullough, D.G., Cavey, J.F., Komsa, R., 2005. Arrival rate of nonindigenous insect species into the United States through foreign trade. Biol. Invas. 7, 323–332.
Nationwide survey for invasive wood-boring and bark beetles (Coleoptera) using traps baited with pheromones and kairomones Eckehard G. Brockerhoff a,*, Diane C. Jones b, Mark O. Kimberley b, D. Max Suckling c, Terry Donaldson d a
Ensis,1 P.O. Box 29237, Fendalton, Christchurch, New Zealand b Ensis,1 Private Bag 3020, Rotorua, New Zealand c HortResearch, P.O. Box 51, Lincoln, New Zealand d AgriQuality, Private Bag 4718, Christchurch, New Zealand
Received 6 August 2005; received in revised form 20 February 2006; accepted 20 February 2006
Abstract Exotic wood borers and bark beetles (WBBB) pose a considerable threat to trees and forests, and the challenge of timely detection and response is significant. The Ministry of Agriculture and Forestry implemented a national surveillance programme for invasive WBBB targeted at species that could become serious pests of New Zealand’s large conifer plantations and unique native forests. The three aims for 2002–2005 were for the programme to act as an early-warning system to detect newly established beetles, to test the efficacy of different lures for established or newly established exotic species and to study the effects of trap placement and proximity of host trees on trap catch in order to improve trap efficiency. For the general surveillance programme, up to 580 funnel traps baited with either a-pinene and ethanol, b-pinene and ethanol, frontalin and ethanol or ipsdienol were placed around New Zealand at high-risk sites including all major seaports, international airports, devanning sites and also in forests near high-risk sites. Additional traps were used to compare these lures with unbaited control traps to assess their effectiveness in catching established exotic WBBB, and to assess the effects of placing traps at varying distances from host trees. Over 27,000 beetles were caught during the general survey from 2002 to 2004, and no new establishments were detected. Between 51% and 88% of all catches were of Scolytinae or Cerambycidae, and most of these were accounted for by the three exotic species Arhopalus ferus, Hylurgus ligniperda and Hylastes ater. Overall, these three species were most attracted to traps baited with a-pinene and ethanol. Catches ‘near’ and ‘far’ from trees differed little for A. ferus and H. ater. H. ligniperda were caught in significantly lower numbers near trees. The results confirm that a trapping programme like the one described here is likely to assist with the early detection of any new establishments, which would improve the chances of successful eradication. # 2006 Elsevier B.V. All rights reserved. Keywords: Exotic species; a-Pinene; b-Pinene; Scolytidae; Cerambycidae
1. Introduction Wood boring and bark beetles are among the most significant forest pests worldwide (Rudinsky, 1962; Wood, 1982a; Gordh and Headrick, 2001). With numerous invasive species, such beetles represent an important threat to the biosecurity of all forested countries (Liebhold et al., 1995; Paine et al., 1997; Haack, 2001; Nowak et al., 2001; Brockerhoff et al., 2006). The most important taxa among invasive wood boring and bark
* Corresponding author Tel.: +64 3 3642949; fax: +64 3 3642812. E-mail address: [email protected] (E.G. Brockerhoff). 1 Ensis is a joint venture between CSIRO and SCION/New Zealand Forest Research Institute Ltd. 0378-1127/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2006.02.046
beetles (WBBB) are bark and ambrosia beetles (Curculionidae: Scolytinae), longhorn beetles (Cerambycidae), and to a lesser extent, other Curculionidae, jewel beetles (Buprestidae), and several other families. For example, 50 exotic Scolytinae are established in the continental U.S. and Canada (Haack, 2001) while New Zealand has 11 exotic Scolytinae (Brockerhoff et al., 2003). Despite a raised international awareness of threats from invasive species, growing international trade and tourism are likely to have caused increasing arrival rates of exotic organisms. High-risk pathways such as air cargo, containers and refrigerated shipments are becoming more common, further enhancing the risk of importing new pests (Dobbs and Brodel, 2004; Work et al., 2005). Forests are an important habitat for much of New Zealand’s unique biodiversity, which includes many threatened, endemic
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species. In addition to the remaining natural forests which cover about 20% of the land, there are over 1.8 million ha of plantation forests that meet most of the country’s wood product needs and also supply forest products for one of the largest export sectors. It is widely recognised that both plantations and natural forests are at risk from invasive species (e.g., Ohmart, 1982; Atkinson and Cameron, 1993). Early detection of new establishments is critical for the most effective implementation of management and eradication efforts (Myers et al., 2000). Consequently, many countries maintain surveillance programmes that involve inspection of forests and trees (e.g., Carter, 1989). An alternative surveillance approach relies on the fact that many WBBB are attracted to host volatiles (e.g., Schroeder and Lindelo¨w, 1989), and sex or aggregation pheromones (Wood, 1982b). The New Zealand Ministry of Agriculture and Forestry (MAF) implemented a nationwide survey for invasive WBBB using funnel traps baited with several attractants that are suitable for a range of high-risk Scolytinae, Cerambycidae and other beetles from important pest genera such as Dendroctonus, Ips and Monochamus. Traps were set up at high-risk sites such as seaports, airports, devanning (container unloading) sites and in forests near highrisk sites. The trapping programme reported here took place from 2002 to 2005 and addressed the following objectives: (1) to act as an early-warning system to detect newly established WBBB, (2) to test the efficacy of species-specific and general lures for exotic WBBB, including species that have become established previously and (3) to study the effects of trap placement, with regard to proximity of host trees. The latter point was addressed to reduce uncertainty about the efficacy of traps placed near host trees because of the potential competition from attractants (i.e., volatiles) emanating from trees. 2. Methods
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Fig. 1. Map of trapping locations and mean catches per trap in 2002–2003 of the three most abundant exotic wood borers and bark beetles, Hylastes ater, Hylurgus ligniperda and Arhopalus ferus. Asterisks show two additional locations where trapping took place in 2003–2004 (catch data for 2003– 2004 are not shown).
throughout New Zealand (Fig. 1) at high-risk sites including all major seaports, international airports, devanning sites where containers are unloaded, and, in 2003–2004, also in forests near high-risk sites. To avoid vandalism, wherever possible, traps were set in secure areas with no public access. Most traps were suspended from steel posts except where other suitable structures, such as wire fences, existed. All traps were set at a height of about 2 m. Trapping took place from October to May (i.e., over the southern hemisphere summer). Traps were checked about every 14 days and samples were sent to Forest Research for identification using standard literature (Klimaszewski and Watt, 1997; and references therein) and reference material in the Forest Research/Ensis Insect Collection.
2.1. Trapping design, lures and study sites 2.2. General survey Trap placement and other specifications were in accordance with the ‘Standard, Specification for Surveillance of Wood Boring and Bark Beetles, New Zealand Ministry of Agriculture and Forestry – Biosecurity Authority, Forest Biosecurity’ (Ministry of Agriculture and Forestry, 2003; and earlier versions), which had been developed with advice from scientists specialising in this field. Eight-unit Lindgren-type funnel traps (PheroTech, Delta, BC, Canada) were used for this study. Lures included general attractants for bark beetles and wood borers as well as two bark beetle pheromones: (1 and 3) a-pinene (95% minus enantiomer, release rate ca. 2 g per day at 20 8C) plus ethanol (release rate ca. 30 mg per day at 20 8C), (2) frontalin (ca. 2.3 mg per day at 20 8C) plus ethanol (as above), (4) ipsdienol (racemic, ca. 0.2 mg per day at 25 8C), (5) bpinene (predominantly minus enantiomer, ca. 100 mg per day at 20 8C) plus ethanol, (6) control (blank). All lures and lure specifications were obtained from PheroTech. Lures were stored in a freezer until used and replaced every 8 weeks (ipsdienol) or 14 weeks (all other lures). Traps were located
In 2002–2003, traps were placed in clusters of four with one each of lures 1–4 (above) at each site. In that year, MAF specified trap positioning in close proximity to high-risk areas but away from standing trees because their presence was thought to reduce trap efficacy. Hence, the trapping protocol was suitable for both established populations as well as for the interception of beetles coming directly from imported freight. A total of 292 traps at 73 site clusters were used from October 2002 to May 2003. Traps were checked about every 2 weeks each giving a total of about 4380 trap readings. In 2003–2004, b-pinene was added because it was found to be particularly attractive to Dendroctonus valens in California (PheroTech red turpentine beetle information sheet). This North American species is of concern because it has become established in China where it is now a significant pest of pine trees. Thus clusters included one each of lures 1–5 (above). A total of 580 traps at 116 site clusters were used for the general survey from December 2003 to May 2004 with 12 trapping
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periods (a total of about 6960 trap readings). The trap placement rules for the general survey were changed to emphasise the detection of established populations, which are most likely to have colonised trees or forests near high-risk sites. Accordingly, in the absence of specific information on optimal trap placement, MAF specified to place traps near potential host trees. 2.3. Effects of trap placement near host trees and comparison of lures with unbaited traps It was unclear whether the placement of traps near trees reduced their efficiency in catching beetles because of the competing attraction of the adjacent host trees, and whether this could compromise the sensitivity of the trapping programme. Therefore, in 2003–2004 additional sets of traps were placed either adjacent to host trees or away from trees. This was done at several sites around Nelson where in previous years catches of the three most common exotic WBBB that are established in New Zealand (Arhopalus ferus Mulsant, Hylastes ater (Paykull) and Hylurgus ligniperda (F.)) have generally been the highest of any location monitored. These additional sets of traps included an unbaited trap (treatment 6 above) to enable a comparison of the effectiveness of the different lures in catching these key WBBB. A total of 80 funnel traps were used to study this aspect. At each of eight replicate sites, five traps, one for each treatment, were placed ‘near’ trees, and five matching traps were placed about 20 m away from trees. Where possible, ‘near’ traps of the on-going 2003–2004 surveillance programme in the Nelson area were used, if these were in fact near trees and if suitable trap locations away from trees existed nearby. This was the case at the Atawhai, Nelson Airport and Rabbit Island (1) sites. Other study sites were added including two additional complete replicates at Rabbit Island (2, 3) and three replicates at Waiwhero Forest west of Nelson. Trapping for this part of the study was carried out during March and April 2004. Additional trapping for A. ferus was undertaken in 2004– 2005 to increase the number of specimens on which the lure comparison was based. Five replicates of lures were used in Eyrewell Forest, Canterbury, from 12 January to 10 February 2005, and another five replicates at Te Puke, Bay of Plenty, from 17 February to 24 March 2005. 2.4. Data analysis Data for the three common introduced species (A. ferus, H. ater and H. ligniperda) were analysed by fitting a log-linear model (McCullagh and Nelder, 1983) for each species. The models contained terms for the site, lure type, and, where applicable, distance from trees (‘near’ and ‘far’). Interactions between these factors were also included in the models. For A. ferus, lure type was analysed with a similar one-way design to accommodate additional data collected in 2004–2005. Models were fitted using the SAS procedure GENMOD (SAS, 2000), with a Poisson error function and the dispersion parameter set to the mean deviance (analysis of deviance or ‘ANODEV’).
Where there were no recorded counts of a species for any lure at a site, that site was dropped from the analysis. Pairwise comparisons were done with LSD tests using log-linear models. To avoid problems with a potentially inflated error rate of multiple comparison tests (Reeve and Strom, 2004), we have used a conservative, Bonferroni-corrected alpha of 0.0167 (0.05/3). Means shown throughout are back-transformed. The Shannon–Wiener diversity index was calculated for species of Scolytinae, Cerambycidae and Platypodinae caught during the regular surveys. 3. Results 3.1. General survey During this survey, at least 82 species of wood boring and bark beetles were trapped, along with many other beetles and other insect orders, which are not addressed further in this paper. The total number of beetles caught was about 19,380 in 2002–2003 and 7967 in 2003–2004. Together, Scolytinae and Cerambycidae accounted for 88% and 51% of catches in the 2 years, respectively (Table 1). One platypodine, the indigenous Platypus apicalis White, was caught (Table 1). Other WBBB (not listed) were mostly from beetle families that infest dead wood, such as Anobiidae and Lyctidae, comprising both indigenous and adventive species. No Buprestidae were caught. The vast majority of these beetles were introduced species. Overall, 99.8% of Scolytinae and 96.3% of Cerambycidae were exotics (Table 1). However, all of these exotic species were known to be established in New Zealand, i.e. no newly established species were detected. The majority of these exotic WBBB are accounted for by just three species, the highly abundant A. ferus (87–99% of the total cerambycid catches in 2002–2003 and 2003–2004), H. ligniperda (54–66% of scolytines) and H. ater (33–35% of scolytines) (Table 1). The dominance of these three species was reflected in the relatively low values of the Shannon–Wiener Index (calculated for Cerambycidae, Scolytinae and Platypodinae) of 1.13 in 2002–2003 and 1.63 in 2003–2004. The three main species, A. ferus, H. ater and H. ligniperda, were present throughout the country but their abundance varied considerably among locations (ANODEV, P < 0.0001) (Fig. 1). H. ater was particularly abundant around Nelson and Invercargill. A. ferus was the most abundant species in the North Island but it was less common in the South Island, except for the Nelson sites where it was particularly abundant. H. ligniperda was very common in the Nelson region, and it was generally more abundant than H. ater except for the far south. There was also considerable variation in catches within a region. For example, in the Nelson region, differences in trap catch among sites were significant for all three species (ANODEV, P < 0.0001 in all cases). A. ferus was most abundant at a fire wood yard at Nelson airport. H. ater occurred at all of the eight Nelson sites and catches differed less among sites than for other species. H. ligniperda was not abundant at Atawhai and Nelson airport but many were caught at both of the plantation forest sites, Rabbit Island and Waiwhero.
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Table 1 Wood boring and bark beetles (Cerambycidae, Scolytinae and Platypodinae) trapped during a New Zealand wide survey Species
Family
Total specimens trapped 2002–2003
Total specimens trapped 2003–2004
Arhopalus ferus (Mulsant)a Hylurgus ligniperda (F.)a Hylastes ater (Paykull)a Xyleborinus saxesenii (Ratzeburg)a Phloeosinus cupressi Hopkinsa Xylotoles griseus (F.) Amasa truncata (Erichson)a Prionoplus reticularis White Calliprason pallidus (Pascoe) Oemona hirta (F.) Bethelium signiferum (Newman)a Platypus apicalis White Hybolasius spp. Pachycotes peregrinus (Chapius) Xylotoles gratus Broun Zorion minutum (F.) Coptodryas eucalyptica (Schedl)a Xylotoles laetus White Callidiopsis scutellaris (F.)a Chaetoptelius mundulus (Broun) Stenopotes spp. Xylotoles humeratus Bates Ambrosiodmus compressusa (Lea) Navomorpha lineata (F.) Ambeodontus tristis (F.) Drototelus elegans (Brookes) Tetrotea spp. Scolytus multistriatus Marshama Leptachrous strigipennis Westwood Hypocryphalus spp. Somatidia spp. Tetrorea sellata Sharp Astetholea lepturoides Bates Coptomma variegatum (F.) Cryphalus wapleri Eichhoffa Metablax cinctiger (White) Xylotoles sp.
Cerambycidae Scolytinae Scolytinae Scolytinae Scolytinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Platypodinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Scolytinae Cerambycidae Scolytinae Cerambycidae Cerambycidae Cerambycidae Cerambycidae Scolytinae Cerambycidae Cerambycidae
7525 6124 3110 9 28 29 51 36 3 16 15 19 1 1 0 3 0 0 7 3 0 0 5 0 1 0 0 2 1 1 0 0 1 1 1 0 0
1768 1082 699 128 74 68 11 17 48 30 27 15 24 15 14 7 10 9 0 3 6 6 0 5 4 3 3 0 1 1 2 2 0 0 0 1 1
Total Scolytinae
9335 (48.2%)
2023 (25.4%)
Total Cerambycidae
7639 (39.4%)
2046 (25.7%)
Total Platypodinae
19 (0.1%)
15 (0.2%)
2387 (12.3%)
3883 (48.7%)
All other Coleoptera a
Exotic species.
3.2. Lure type The lure type used had highly significant effects on trap catch in all three main species (ANODEV, P < 0.001). aPinene plus ethanol and b-pinene plus ethanol were the most attractive lures for A. ferus (Table 2; Fig. 2). It is also noteworthy that non-chemical cues or random trap encounters are important in this species as indicated by catches of the control trap (Fig. 2). There were conflicting results for H. ater because in 2002–2003 most beetles were caught to frontalin plus ethanol and ipsdienol whereas in 2003–2004, the most catches were made to a-pinene plus ethanol and to b-pinene plus ethanol (Table 2; Fig. 3). It is possible that confounding factors relating to trap placement (see below) explain the high
catches to frontalin and ipsdienol, and overall, a-pinene plus ethanol is probably the best lure for this species. The lack of any noticeable differences (in 2003–2004) among catches to frontalin plus ethanol, ipsdienol and the control suggest that these lures are not adding any attraction over the purely visual cues of the funnel trap. Black funnel traps are thought to mimic the visual cues presented by the dark silhouettes of tree boles that contribute to the attraction of bark beetles (e.g., Goyer et al., 2004). H. ligniperda was clearly most attracted by apinene plus ethanol, as shown consistently in all three trials (Table 2; Fig. 4). Catches to b-pinene plus ethanol and ipsdienol were only marginally but still significantly better than the control (Fig. 4). Catches to the control were very small suggesting that visual cues of the funnel traps alone are not
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Table 2 Mean catches per trap during general surveys in 2002–2003 and 2003–2004 of the most abundant wood boring and bark beetle species Lure
Arhopalus ferus
Hylastes ater
Hylurgus ligniperda
2002–2003 a-Pinene + ethanol Frontalin + ethanol Ipsdienol
26.9 (1.7)a 16.3 (1.0)b 18.4 (1.2)b
4.4 (0.5)b 6.8 (0.7)a 8.6 (0.9)a
24.2 (2.5)a 18.3 (1.9)b 9.7 (1.0)c
2003–2004 a-Pinene + ethanol Frontalin + ethanol Ipsdienol b-Pinene + ethanol
7.1 3.5 3.3 11.6
4.9 1.5 0.7 1.9
(1.6)ab (0.8)bc* (0.7)c (2.6)a*
(0.3)a (0.4)b (0.2)b (0.5)b
8.5 1.5 2.1 2.1
(1.5)a (0.3)b (0.4)b (0.4)b
Lindgren traps were baited with one of four different lures. Values in a column followed by the same letter do not differ significantly (a = 0.0167) within a year according to pairwise comparison analyses (LSD) performed using log-linear models. * These treatments differed from a-pinene + ethanol at P = 0.020–0.025.
Fig. 2. Mean trap catch of Arhopalus ferus to different lures in 2003–2004 and 2004–2005 (n = 225 beetles, 21 sites with catches excluding 5 sites with no trapped beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 14.1, F = 8.1, P < 0.0001).
important in this species. Although results from 2002 to 2003 (Table 2) suggest that frontalin plus ethanol is attractive, this was probably either due to the ethanol content or a trap placement artefact (see below).
Fig. 4. Mean trap catch of Hylurgus ligniperda to different lures in 2003–2004 (n = 3316 beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 1464, F = 519.7, P < 0.0001).
3.3. Effect of trap placement near host trees The total catches over the 6-week trapping period in this trial were 3957 individuals of the three species (A. ferus, H. ater and H. ligniperda) targeted for this aspect of the study. Catches of H. ater ‘near’ and ‘far’ from trees differed little (Table 3; ANODEV, mean deviance = 1.6, F = 0.5, P = 0.484). Differences due to distance from trees were significant for A. ferus although the effect size was small (Table 3; ANODEV, mean deviance = 4.5, F = 4.5, P = 0.027). The difference was considerable for H. ligniperda (Table 3; ANODEV, mean deviance = 995.7, F = 353.3, P < 0.0001) but this was mostly due to the very large catch of one trap (with 1403 beetles) out of the eight ‘far’ traps, which was paired with a ‘near’ trap with a moderate catch of 41 beetles. Furthermore, this ‘near’ trap was located near a large kanuka (Kunzea ericoides) tree, which appears to have obscured (chemically and/or visually) this trap to some degree. When this pair is excluded, then the overall difference between ‘near’ and ‘far’ is much smaller (i.e., less than 50% difference). It is also of interest that the type of land or habitat ‘far’ from trees has a considerable influence on the size and ‘direction’ of the effect. At the Atawhai site ‘far’ traps set up in a pasture block caught fewer beetles (only four individuals of the three main species) than the ‘near’ traps set up in an adjacent pine stand (which caught 28 beetles). This contrasts with the overall result of somewhat greater catches ‘far’ from trees, which reflects the situation of ‘far’ sites that had abundant woody debris and associated WBBB. Presumably this contrasting effect of the ‘near/far’ habitat is the reason for the significant Table 3 Mean catch of three beetle species in paired traps located ‘near’ or ‘far’ from trees
Fig. 3. Mean trap catch of Hylastes ater to different lures in 2003–2004 (n = 574 beetles). Columns sharing a letter do not differ significantly (a = 0.0167) according to pairwise comparison analyses (LSD) performed using log-linear models (ANODEV, mean deviance = 56.6, F = 18.11, P < 0.0001).
Distance from trees
Arhopalus ferus
Hylastes ater
Hylurgus ligniperda
Near (<3 m) Far (20 m)
0.38 (0.07)ba 0.65 (0.12)a
4.27 (0.62)a 4.75 (0.69)a
2.16 (0.29)b 7.12 (0.96)a
Values in a column followed by the same letter do not differ significantly (a = 0.05) according to analysis of deviance using log-linear models.
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distance site interaction of the ANODEV for H. ligniperda (mean deviance = 139.3, F = 49.45, P < 0.0001).
4. Discussion The results of this study confirm that odourant-baited traps can be used effectively for a nationwide surveillance programme to monitor populations of exotic beetles, as well as native species, that infest the wood and bark of trees. Host plant volatiles, particularly a-pinene plus ethanol, proved to be suitable lures for beetles associated with conifers. The attraction of secondary bark beetles of conifers to host odours, particularly to a-pinene alone or in combination with ethanol, is well documented. For H. ater and H. ligniperda, this was shown by Perttunen (1957) and Petrice et al. (2004), respectively. Interestingly, many beetles were caught using unbaited funnel traps, which indicates that visual cues (traps mimics tree trunks) and random trap encounters are also involved. The more species-specific beetle pheromones did not consistently improve catches over unbaited traps for any of the species of which substantial numbers were trapped. This also agrees with previous studies of the secondary species we encountered (e.g., Petrice et al., 2004). However, had there been new establishments of any bark beetle species attracted to the pheromones we tested here, these lures probably would have been more effective than the host plant volatiles. The pheromones chosen are used by many of the most notorious conifer pests from the genera Ips, Dendroctonus and Monochamus (El-Sayed, 2005) and hence their use in a trapping programme to detect new establishments is warranted. Where specific pheromones or other attractants are known for new incursions of exotic species, the best approach is likely to be based on such specific attractants. An example of a bark beetle for which a pheromone is available, and which is of particular relevance to trees in New Zealand, is the smaller elm bark beetle (Scolytus multistriatus (Marsham)). Its pheromone is currently used for surveys in Auckland, New Zealand. In other cases, long range attractants may not be known, for example for the Asian longhorn beetle (Anoplophora glabripennis), and surveys are more cumbersome because they must rely on evidence of tree damage for detection and delimitation. Differences among the relative catches to the different lures used are probably related to: (i) stochastic trapping events that are likely to be most apparent when samples are small, and (ii) trap placement effects. Some of the traps used in port environs in 2002–2003 were positioned near solid fences, walls, or even inside a warehouse. Although it was not possible to retrospectively analyse the degree to which traps positioned in this way influenced the comparison among lures, it can be expected that such traps were less effective at disseminating pheromone and probably less accessible than traps placed in an open area. Such problems were avoided during 2003–2004, and in that year the results were more consistent with other studies. The reason for the greater overall catches in 2002–2003 than in 2003–2004 are probably due to the traps having been placed in
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open, semi-industrial yards where logs and wood were often present versus near trees and other vegetation, respectively. The results of the trial with paired traps positioned near trees and far from trees suggests that this has some, relatively small effect. The major driver for the overall greater ‘far’ catch probably reflects the situation in clearfelled areas (which applied to five of the eight sites) where the abundance of woody debris provided numerous breeding sites and, ultimately, large bark beetle populations. Taken together, the results give no indication that traps placed near host trees (pines in the present study) are much less effective than those about 20 m away. However, it would be of interest to conduct a similar study with traps also placed at greater distances from trees (e.g., 100 m). Overall, the results indicate that a trapping programme for WBBB with traps being placed near trees are likely to yield fewer individuals but more species than when traps are placed in tree-less areas, but there was no clear indication of major negative interference from host trees. A remarkable result was the large number of exotic species that were trapped, their high proportion among the overall catch (over 96% of Scolytinae and Cerambycidae specimens were from exotic species), and the clear dominance of just three species. This reflects the relatively low number of exotic WBBB present in New Zealand (e.g., Brockerhoff et al., 2003), which is probably a result of the geographic isolation of the country and a relatively successful quarantine programme. It also reflects the fact that the attractants used are typically associated with conifer-infesting beetles and conifers, in particular Pinaceae, which are not present in the New Zealand flora, except as introduced trees in plantation forests, shelter belts, and as amenity trees. a-Pinene is mainly attractive to beetles infesting conifers where this monoterpene is common whereas it can be repellent to beetles attacking broadleaved trees (see Schroeder and Lindelo¨w, 1989), which do not usually contain a-pinene. Given the significance of the threat posed by exotic WBBB and their associated pathogens to the plantations of exotic conifers, amenity trees and, for some, also to New Zealand’s native forests, it is critical to remain vigilant and to avoid the establishment of any additional such species. Although relatively expensive, a trapping programme like the one described here is likely to assist with the early detection of any new establishments, which would improve the chances of successful eradication. Acknowledgements We would like to thank Davor Bejakovich and Brendan Murphy (Ministry of Agriculture and Forestry – Biosecurity NZ) for assistance with the co-ordination of the study, Robert Rabaglia (Maryland Dept. of Agriculture) for advice on WBBB trapping designs, the staff of AgriQuality New Zealand for conducting the nationwide survey, Nadine Fletcher, David Logan, Vanessa Mitchell, Peter Shaw, Paula Thomson, and Roger Wallis (HortResearch) for field assistance, and John Bain (Ensis) for assistance with insect identification. Thanks also to John Bain, Brendan Murphy, Mark Ross (Ministry
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of Agriculture and Forestry – Biosecurity NZ), and Andrea Stephens (HortResearch) for reviewing the manuscript. Funding from the Ministry of Agriculture and Forestry and the New Zealand Foundation for Research, Science and Technology (under contract C04X0302) is gratefully acknowledged. References Atkinson, I.A.E., Cameron, E.K., 1993. Human influence on the terrestrial biota and biotic communities of New Zealand. Trends Ecol. Evol. 8, 447–451. Brockerhoff, E.G., Knı´zˇek, M., Bain, J., 2003. Checklist of indigenous and adventive bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) of New Zealand and interceptions of exotic species (1952– 2000). N.Z. Entomol. 26, 29–44. Brockerhoff, E.G., Bain, J., Kimberley, M., Knı´zˇek, M., 2006. Interception frequency of exotic bark and ambrosia beetles (Coleoptera: Scolytinae) and relationship with establishment in New Zealand and worldwide. Can. J. For. Res. 36, 289–298. Carter, P.C.S., 1989. Risk assessment and pest detection surveys for exotic pests and diseases which threaten commercial forestry in New Zealand. N.Z. J. For. Sci. 19, 353–374. Dobbs, T.T., Brodel, C.F., 2004. Cargo aircraft as a pathway for the entry of nonindigenous pests into South Florida. Florida Entomol. 87, 65–78. El-Sayed, A.M., 2005. The Pherobase: Database of Insect Pheromones and Semiochemicals.
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