Glyphosate-induced changes in the attack success and development of the mountain pine beetle and impact of its natural enemies

Roundup (active ingredient glyphosate) administered into the sapwood around the root collar of lodgepole pine trees, Pinus contorta var. latifolia Engelm., was investigated as a tool for creating trap trees for the mountain pine beetle (MPB), Dendroctonus ponderosae Hopk. MPB's attacked semiochemical-baited, glyphosate-treat trees before attacking baited control trees. Bark samples disclosed an increase in survival of MPB eggs and early instar larvae, enhanced larval development and increased attacks by insect parasites and predators in treated trees. The braconid wasp, Coeloides dendroctoni Cush., parasitized MPB larvae found at high densities in treated trees two months following attack. The dipteran predator, Medetera aldrichii Wh., was only found in treated trees. Increased competition by Ips pini (Say) had a negative impact on MPB survivorship. The enhanced impact of insectan agents apparently offset any glyphosate-induced gains in MPB survival or development, but did not cause a significant reduction in MPB emergence.     

Interruption of aggregation pheromone in Ips typographus (L.) (Col. Scolytidae) by non-host bark volatiles

Abstract 1 The antennally active nonhost bark volatiles (NHVs): trans‐conophthorin (tC), C₆‐alcohols (green leaf volatiles; GLVs) and C₈‐alcohols, were tested for their ability to reduce attraction of the spruce bark beetle Ips typographus (L) (Col. Scolytidae) to its pheromone sources in both laboratory walking bioassy and field trapping experiments. 2 In the walking bioassay with I. typographus females, individual NHVs such as tC, 3‐octanol and 1‐octen‐3‐ol, and the unsuitable host signal, verbenone (Vn), were inactive at the doses tested. However, the blend of C₆‐alcohols (3GLVs) and all the binary, ternary, or quarternary blends significantly reduced the female attraction to the pheromone sources. 3 In the field trapping experiments, individual NHV signals (tC, C6‐alcohols and C₈‐alcohols) all reduced catch of I. typographus in pheromone‐baited traps, with their inhibitory effects similar to that of the known inhibitor, Vn. The binary, ternary or quarternary combinations of these NHV signals or Vn, all caused significantly stronger reductions in trap catches than the individual signals. The blends showed similar levels of interruption, except the binary blend of C₈‐alcohols (2C8OH) and Vn. 4 Difference in trapping mechanism between pipe traps (attraction and landing) and Lindgren funnel traps (attraction) did not affect the pattern of inhibition of these active NHV signals and Vn. 5 These behaviourally active nonhost volatiles and Vn might be used effectively to protect spruce trees or stands against attacks by I. typographus.     

Olfactory recognition and behavioural avoidance of angiosperm nonhost volatiles by conifer-inhabiting bark beetles

Abstract 1 When searching for suitable hosts in flight, especially in mixed forests, conifer‐inhabiting bark beetles will encounter not only suitable host trees and their odours, but also unsuitable hosts and nonhost trees. Rejection of these trees could be based on an imbalance of certain host characteristics and/or a negative response to some nonhost stimuli, such as nonhost volatiles (NHV). 2 Recent electrophysiological and behavioural studies clearly indicate that conifer‐inhabiting bark beetles are not only able to recognize, but also to avoid, nonhost habitats or trees by olfactory means. Green leaf volatiles (GLV), especially C₆‐alcohols, from the leaves (and partly from bark) of nonhost angiosperm trees, may represent nonhost odour signals at the habitat level. Specific bark volatiles such as trans‐conophthorin, C₈‐alcohols, and some aromatic compounds, may indicate nonhosts at the tree species level. Flying bark beetles are also capable of determining whether a possible host is unsuitable by reacting to signals from conspecifics or sympatric heterospecifics that indicate old or colonized host tree individuals. 3 Combined NHV signals in blends showed both redundancy and synergism in their inhibitory effects. The coexistence of redundancy and synergism in negative NHV signals may indicate different functional levels (nonhost habitats, species, and unsuitable hosts) in the host selection process. Combinations of NHV and verbenone significantly reduced the number of mass attacked host trees or logs on several economically important species (e.g. Dendroctonus ponderosae, Ips typographus, and I. sexdentatus). 4 We suggest a semiochemical‐diversity hypothesis, based on the inhibition by NHV of bark beetle host‐location, which might partly explain the lower outbreak rates of forest insects in mixed forests. This ‘semiochemical‐diversity hypothesis’ would provide new support to the general ‘stability‐diversity hypothesis’. 5 Natural selection appears to have caused conifer‐inhabiting bark beetles to evolve several olfactory mechanisms for finding their hosts and avoiding unsuitable hosts and nonhost species. NHV and unsuitable host signals have potential for use in protecting trees from attack. The use of these signals may be facilitated by the fact that their combination has an active inhibition radius of several metres in trap test, and by the observation of area effects for several trees near inhibitor soruces in tree protection experiments. Furthermore, incorporation of negative signals (such as NHV and verbenone) and pheromone‐based mass‐trapping in a ‘push–pull’ fashion may significantly increase the options for control against outbreaks of conifer‐inhabiting bark beetles, especially in high risk areas.     

Performance of the tree‐killing bark beetles Ips typographus and Pityogenes chalcographus in non‐indigenous lodgepole pine and their historical host Norway spruce

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Area‐wide application of verbenone‐releasing flakes reduces mortality of whitebark pine Pinus albicaulis caused by the mountain pine beetle Dendroctonus ponderosae

• 1 DISRUPT Micro‐Flake Verbenone Bark Beetle Anti‐Aggregant flakes (Hercon Environmental, Inc., Emigsville, Pennsylvania) were applied in two large‐scale tests to assess their efficacy for protecting whitebark pine Pinus albicaulis Engelm. from attack by mountain pine beetle Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae) (MPB). At two locations, five plots of equivalent size and stand structure served as untreated controls. All plots had early‐ to mid‐outbreak beetle populations (i.e. 7.1–29.2 attacked trees/ha). Verbenone was applied at 370 g/ha in both studies. Intercept traps baited with MPB aggregation pheromone were placed near the corners of each plot after the treatment in order to monitor beetle flight within the plots. Trap catches were collected at 7‐ to 14‐day intervals, and assessments were made at the end of the season of stand structure, stand composition and MPB attack rate for the current and previous years.
• 2 Applications of verbenone flakes significantly reduced the numbers of beetles trapped in treated plots compared with controls at both sites by approximately 50% at the first collection date.
• 3 The applications also significantly reduced the proportion of trees attacked in both Wyoming and Washington using the proportion of trees attacked the previous year as a covariate in the model for analysis of current year attack rates; in both sites, the reduction was ≥ 50%.
• 4 The flake formulation of verbenone appears to have promise for area‐wide treatment by aerial application when aiming to control the mountain pine beetle in whitebark pine forests.

     

Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatiles

We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple-funnel traps baited with the attractive host volatile α-pinene. A combination of four GLV alcohols, 1-hexanol ( E )-2-hexen-1-ol ( Z )-2-hexen-1-ol, and ( Z )-3-hexen-1-ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and ( E )-2-hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with α-pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer-attacking bark beetles (Scolytidae).     

Response of Dendroctonus brevicomis to different release rates of nonhost angiosperm volatiles and verbenone in trapping and tree protection studies

A blend of eight nonhost angiosperm volatiles (benzyl alcohol, benzaldehyde, guaiacol, nonanal, salicylaldehyde, (E)‐2‐hexenal, (E)‐2‐hexen‐1‐ol and (Z)‐2‐hexen‐1‐ol) without [NAV] and with [NAVV] (–)‐verbenone (4,6,6‐trimethylbicyclo[3.1.1]hept‐3‐en‐2‐one) were tested at low (L), medium (M) and high (H) release rates for their ability to reduce attraction of western pine beetle, Dendroctonus brevicomis LeConte, to attractant‐baited (exo‐brevicomin [racemic, 3 mg/d], frontalin [racemic, 3 mg/d] and myrcene [18 mg/d]) multiple funnel traps. NAV‐L (40 mg/d) had no significant effect. Verbenone alone (50 mg/d) and NAV‐M (240 mg/d) both significantly reduced attraction, but no significant difference was observed between the two treatment means. NAV‐H (430 mg/d) significantly reduced catches by ～60% and 78% compared to verbenone alone and the baited control, respectively. In a second experiment, combining (–)‐verbenone with NAV (NAVV) increased the effects observed in Experiment 1. NAVV‐M (240 mg/d) resulted in an ～69% and 83% reduction in trap catch compared to verbenone alone and the baited control, respectively. Significantly fewer D. brevicomis were captured in NAVV‐H (430 mg/d) than any other treatment resulting in an ～93% reduction in trap catch compared to the baited control. In a third experiment, NAVV was tested at three release rates for its ability to protect individual ponderosa pines, Pinus ponderosa Dougl. ex Laws., from attack by D. brevicomis. Cumulative release rates varied in direct proportion to tree diameter, but represented quarter, half and full NAVV rates. NAVV significantly reduced the density of D. brevicomis attacks, D. brevicomis successful attacks, and levels of tree mortality on attractant‐baited trees. Only three of 15 NAVV‐treated trees died from D. brevicomis attack while ～93% mortality (14/15) was observed in the untreated, baited control. Quarter and half rates were ineffective for reducing tree mortality.     

Responses of Dendroctonus brevicomis (Coleoptera: Curculionidae) in behavioral assays: implications to development of a semiochemical-based tool for tree protection

Currently, techniques for managing western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae, Scolytinae), infestations are limited to tree removals (thinning) that reduce stand density and presumably host susceptibility, and/or the use of insecticides to protect individual trees. There continues to be significant interest in developing an effective semiochemical-based tool for protecting trees from D. brevicomis attack, largely as an alternative to conventional insecticides. The responses of D. brevicomis to tree volatiles and verbenone were documented in eight experiments (trapping assays) conducted over a 4-yr period in which 88,942 individuals were collected. Geraniol, a tree volatile unique to Pinus ponderosa that elicits female-specific antennal responses in D. brevicomis, did not affect D. brevicomis behavior. Blends of two green leaf alcohols [hexanol + (Z)-3-hexen-1-ol] tested at two release rates (5.0 and 100.0 mg/d) had no effect on the response of D. brevicomis to attractant-baited traps. A nine-component blend [benzaldehyde, benzyl alcohol, guaiacol, nonanal, salicylaldehyde, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (-) -verbenone; NAVV] and subsequent revisions of this blend disrupted the response of D. brevicomis to attractant-baited traps in all experiments. The inhibitory effect of a revised five-component blend [nonanal, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (-)-verbenone; NAVV5] on the response of mountain pine beetle, D. ponderosae Hopkins, to attractant-baited traps was also documented. Acetophenone significantly reduced D. brevicomis attraction, but was not as effective as verbenone alone. Acetophenone increased the effectiveness of NAVV5 in one of two experiments. Furthermore, by adding acetophenone to NAVV5 we were able to remove the aldehydes from NAVV5 without compromising effectiveness, resulting in a novel four-component blend [acetophenone, (E)-2-hexen-1-ol + (Z)-2-hexen-1-ol, and (-)-verbenone; Verbenone Plus]. We discuss the implications of these and other results to development of Verbenone Plus as a semiochemical-based tool for management of D. brevicomis and D. ponderosae infestations.     

Verbenone-releasing flakes protect individual Pinus contorta trees from attack by Dendroctonus ponderosae and Dendroctonus valens (Coleoptera: Curculionidae, Scolytinae)

1 In a study site in interior northern California, twenty individual lodgepole pines Pinus contorta were sprayed with a suspension of DISRUPT Micro‐Flake^® Verbenone (4,6,6‐trimethylbicyclo(3.1)hept‐3‐en‐2‐one) Bark Beetle Anti‐Aggregant flakes (Hercon Environmental, Emigsville, Pennsylvania) in water, with sticker and thickener, from ground level to a height of 7 m. Twenty trees sprayed with just water, sticker and thickener served as controls. All trees were baited immediately after spraying with mountain pine beetle Dendroctonus ponderosae aggregation pheromone lures, and lures were refreshed after 4 weeks. 2 Trees treated with verbenone had significantly lower attack density by D. ponderosae than controls at 2, 4, 6 and 8 weeks after application of flakes. 3 None of the treated trees was attacked by red turpentine beetle Dendroctonus valens, whereas control trees averaged nearly two D. valens attacks per tree, 8 weeks after treatment. 4 A dry frass index, used to predict ultimate tree mortality, was significantly higher in control trees than treated trees for all four sampling intervals. This index proved to be a significant predictor of ultimate tree mortality. 5 Ten months after application, treated trees showed significantly lower mortality than control trees.     

Fungal,host and non-host volatiles modify attraction of the walnut twig beetle,Pityophthorus juglandis,to pheromone lures

1. Thousand Cankers Disease (TCD) of walnut trees is caused by the pathogenic fungus Geosmithia morbida vectored by the walnut twig beetle (WTB) Pityophthorus juglandis. Monitoring efforts for WTB rely on pheromone-baited traps, but lures are likely effective at attracting beetles only over short distances. Fungal-derived kairomones may increase the efficacy of current lures, while additional volatiles may repel beetles from valuable trees.
2. The objective of this study was to determine the extent to which fungal, host and non-host volatiles modify the attraction of WTB to pheromone-baited traps. A trapping study that combined fungal, host-associated and non-host compounds with WTB-pheromone lures was conducted over three years in black walnut plantations experiencing a TCD outbreak in Walla Walla, WA.
3. Traps baited with pheromone and G. morbida volatiles (i.e., isoamyl and isobutyl alcohol) consistently attracted more WTB, while other fungal volatiles inconsistently increased attraction compared to those baited with pheromone lure alone. This is the first field study that demonstrates fungal volatiles can increase the attraction of a bark beetle to its pheromone in a hardwood system.
4. One fungal (benzyl alcohol) and two additional volatiles (limonene, piperitone) repelled WTB from pheromone-baited traps. Although limonene is known to repel WTB, this is the first demonstration that benzyl alcohol and piperitone repel a bark beetle.
5. Fungal volatiles may increase the efficacy of monitoring efforts and may play an important role in management tactics for WTB, especially in detecting the introduction and establishment of nascent populations and protecting trees from colonizing beetles.

     

Response of the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), to conophthorin and other angiosperm bark volatiles in the avoidance of non-hosts

1 Seventeen non‐host angiosperm bark volatiles, seven of which are antennally active to Ips pini (Say), the pine engraver (PE), were tested for their ability to disrupt the response of the PE to pheromone‐baited traps. 2 Four green leaf volatiles (GLVs) were tested [1‐hexanol (Z)‐3‐hexen‐1‐ol, hexanal, and (E)‐2‐hexenal]. None had any disruptive effect singly, as a group or in all possible blends based on functional groups, despite the fact that the two aldehydes were antennally active. These compounds may have, in some instances, actually masked the disruptive effect of other compounds. The PE thus differs in its response from other Scolytidae, including other Ips spp. 3 Eight non‐host volatiles that were antennally active to other bark beetles, but not to PEs, had no disruptive effect, validating the use of coupled gas chromatographic‐electroantennographic detection analyses to detect compounds with potential behavioural activity. 4 The bicyclic spiroacetal conophthorin, (E)‐7‐methyl‐1,6‐dioxaspiro[4.5]decane, was disruptive when tested alone. When blends of two aldehydes [salicylaldehyde and nonanal] plus an alcohol and a phenol [benzyl alcohol and guaiacol] were combined with conophthorin, an enhanced disruptive effect was revealed. No single compound, other than conophthorin, disrupted the pheromone‐positive response and no blend that did not contain conophthorin was consistently disruptive to both sexes. Conophthorin seems to be a critical component in the non‐host angiosperm message for I. pini during its host selection phase. 5 Combination of the repellent synomones, verbenone and ipsenol, with the five disruptive non‐host volatiles may provide a potent treatment to protect trees, logs or stands from attack by the PE.     

Non-Host Volatile Blend Optimization for Forest Protection against the European Spruce Bark Beetle,Ips typographus

Conifer feeding bark beetles (Coleoptera, Curculionidae, Scolytinae) pose a serious economic threat to forest production. Volatiles released by non-host angiosperm plants (so called non-host volatiles, NHV) have been shown to reduce the risk of attack by many bark beetle species, including the European spruce bark beetle, Ips typographus. However, the most active blend for I. typographus, containing three green leaf volatiles (GLVs) in addition to the key compounds trans-conophthorin (tC) and verbenone, has been considered too expensive for use in large-scale management. To lower the cost and improve the applicability of NHV, we aim to simplify the blend without compromising its anti-attractant potency. Since the key compound tC is expensive in pure form, we also tested a crude version: technical grade trans-conophthorin (T-tC). In another attempt to find a more cost effective substitute for tC, we evaluated a more readily synthesized analog: dehydro-conophthorin (DHC). Our results showed that 1-hexanol alone could replace the three-component GLV blend containing 1-hexanol, (3Z)-hexen-1-ol, and (2E)-hexen-1-ol. Furthermore, the release rate of tC could be reduced from 5 mg/day to 0.5 mg/day in a blend with 1-hexanol and (–)-verbenone without compromising the anti-attractant activity. We further show that T-tC was comparable with tC, whereas DHC was a less effective anti-attractant. DHC also elicited weaker physiological responses in the tC-responding olfactory receptor neuron class, providing a likely mechanistic explanation for its weaker anti-attractive effect. Our results suggest a blend consisting of (–)-verbenone, 1-hexanol and technical trans-conophthorin as a cost-efficient anti-attractant for forest protection against I. typographus.     

Primary attraction and kairomonal host discrimination in three species of Dendroctonus (Coleoptera: Scolytidae)

Abstract 1 Synthetic blends of bole and foliage volatiles of four sympatric species of conifers were released from pheromone‐baited multiple‐funnel traps to determine if three species of tree‐killing bark beetles (Coleoptera: Scolytidae): (i) exhibited primary attraction to volatiles of their hosts and (ii) discriminated among volatiles of four sympatric species of host and nonhost conifers. 2 Bole and foliage volatiles from Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, increased the attraction of coastal and interior Douglas‐fir beetles, Dendroctonus pseudotsugae Hopkins, to pheromone‐baited traps. Primary attraction to bole volatiles was observed in interior D. pseudotsugae. Beetles were significantly less attracted to the pheromone bait when it was combined with volatiles of lodgepole pine, Pinus contorta var. latifolia Engelm. or interior fir, Abies lasiocarpa × bifolia. 3 The monoterpene myrcene synergized attraction of mountain pine beetles, Dendroctonus ponderosae Hopkins, to their aggregation pheromones, but there was no evidence of primary attraction to host volatiles or discrimination among volatiles from the four conifers. 4 There was significant primary attraction of the spruce beetle, Dendroctonus rufipennis Kirby, to bole and foliage volatiles of interior spruce, Picea engelmannii × glauca, but beetles did not discriminate among volatiles of four sympatric conifers when they were combined with pheromone baits. 5 Our results indicate that host volatiles act as kairomones to aid pioneer Douglas‐fir beetles and spruce beetles in host location by primary attraction, and that their role as synergists to aggregation pheromones is significant. For the mountain pine beetle, we conclude that random landing and close range acceptance or rejection of potential hosts would occur in the absence of aggregation pheromones emanating from a tree under attack.     

Pine monoterpenes and pine bark beetles: a marriage of convenience for defense and chemical communication

Pine-feeding bark beetles (Coleoptera: Scolytidae) interact chemically with their host pines (Coniferales: Pinaceae) via the behavioral, physiological, and biochemical effects of one class of isoprenoids, the monoterpenes and their derivatives. Pine monoterpenes occur in the oleoresin and function as behaviorally active kairomones for pine bark beetles and their predators, presenting a classic example of tri-trophic chemical communication. The monoterpenes are also essential co-attractants for pine bark beetle aggregation pheromones. Ironically, pine monoterpenes are also toxic physiologically to bark beetles at high vapor concentrations and are considered an important component of the defense of pines. Research over the last 30 years has demonstrated that some bark beetle aggregation pheromones arise through oxygenation of monoterpenes, linking pheromone biosynthesis to the host pines. Over the last 10 years, however, several frequently occurring oxygenated monoterpene pheromone components (e.g., ipsenol, ipsdienol and frontalin) have also been shown to arise through highly regulated de novo pathways in the beetles (reviewed in Seybold and Tittiger, 2003). The most interesting nexus between these insects and their plant hosts involves the late-stage reactions in the monoterpenoid biosynthetic pathway, during which isomeric dimethylallyl diphosphate and isopentenyl diphosphate are ultimately elaborated to stereospecific monoterpenes in the trees and to hydroxylated monoterpenes or bicyclic acetals in the insects. There is signal stereospecificity in both production of and response to the monoterpenoid aggregation pheromones of bark beetles and in response to␣the monoterpenes of the pines. In the California fivespined ips, Ips paraconfusus, we have discovered a number of cytochome P450 genes that have expression patterns indicating that they may be involved in detoxifying monoterpene secondary metabolites and/or biosynthesizing pheromone components. Both processes result in the production of oxygenated monoterpenes, likely with varying degrees of stereospecificity. A behavioral analysis of the stereospecific response of I. paraconfusus to its pheromone is providing new insights into the development of an efficacious bait for the detection of this polyphagous insect in areas outside the western United States. In contrast, a Eurasian species that has arrived in California, the Mediterranean pine engraver, Orthotomicus (Ips) erosus, utilizes both a monoterpenoid (ipsdienol) and a hemiterpenoid (2-methyl-3-buten-2-ol) in its pheromone blend. The stereospecificity of the response of O. erosus to the monoterpenoid appears to be the key factor to the improved potency of the attractant bait for this invasive species.Dedicated to Professor David L. Wood on the occasion of his 75th birthday, January 8, 2006     

Sub-lethal plant defences: the paradox remains

Lodgepole pine (Pinus contorta) trees of two different seed origins, one a poor quality host (Alaskan lodgepole pine), the other a good quality host (south coastal lodgepole pine), were infested with known numbers of eggs of the pine beauty moth, Panolis flammea. Each tree had paired sleeves, one allowing access by invertebrate predators, the other denying this access. When the sleeves were removed, the numbers of larvae surviving, their weights and developmental stages were assessed. Larvae reared on south coastal lodgepole pine (SLP) in the absence of predators were significantly heavier and had significantly better survival rates than larvae reared in comparable conditions on Alaskan lodgepole pine (ALP). However, in the open sleeves, although the larvae reared on SLP were significantly heavier than those on ALP, survival was significantly greater on ALP. Thus predation was greater on the faster developing larvae on the better quality host. These results indicate that slow growth by a herbivore does not necessarily result in greater vulnerability to predators.     

Test of nonhost angiosperm volatiles and verbenone to protect trap trees for Sirex noctilio (Hymenoptera: Siricidae) from attacks by bark beetles (Coleoptera: Scolytidae) in the northeastern United States

Sirex noctilio F. (Hymenoptera: Siricidae) is an invasive woodwasp, currently established in northeastern North America. In other regions of the world, stressed trap trees are used to monitor populations of S. noctilio and to provide inoculation points for the biological control nematode Deladenus siricidicola Bedding. However, the operational use of trap trees for S. noctilio in North America may be compromised by the large community of native organisms that inhabit stressed and dying pine trees. Common bark beetles such as Ips pini (Say) and Ips grandicollis (Eichhoff) (Coleoptera: Scolytidae) could potentially compete with S. noctilio and associates for resources on trap trees, possibly reducing the efficacy of trap trees as habitats for the woodwasp. In an attempt to develop a technology to mitigate this potential issue, three common semiochemical interruptants--conophthorin, green leaf volatile mix, and verbenone--were tested for effectiveness in reducing arrivals of I. pini and I. grandicollis on trap trees treated with herbicides in northeastern United States. In addition, the effects of these compounds were determined independently with pheromone-baited multiple-funnel traps. None of the interruptants reduced numbers of I. pini or I. grandicollis either arriving on trap trees or caught in pheromone-baited traps. However, verbenone increased catches of I. grandicollis in traps baited with its pheromone, ipsenol. The mix of green leaf volatiles reduced catches of a native ambrosia beetle, Gnathotrichus materiarius (Fitch), whereas verbenone reduced trap catches of an exotic ambrosia beetle, Xylosandrus germanus (Blandford). Catches of X. germanus in traps adjacent to trap trees were enhanced with conophthorin.     

Semiochemical diversity diverts bark beetle attacks from Norway spruce edges

The semiochemical diversity hypothesis (SDH) states that interference with host‐selection from non‐host volatiles (NHV) is an important mechanism for associational resistance. Inhibition of bark beetle attraction to point sources by non‐host volatiles (NHV) is well established and might be a signal serving in host‐selection also at the habitat scale. In forests dominated by Norway spruce in middle and northern Europe (N Slovakia 2006 & 2007, SE Sweden 2007), we applied a blend of NHV and verbenone, released from dispensers fixed at 2 and 6 m height at forest edges with high Ips typographus populations. In Slovakia, three different doses (0.2–0.7 dispensers/m forest edge) were tested in 20‐tree zones of spruce stand edges. The Swedish experiments used only the middle dose. In Slovakia, there was high tree mortality but dispensers with the anti‐attractants reduced killed trees in a dose‐dependent manner. The reduction in tree killing ranged from 35 to 76% compared to untreated zones. Regression analysis of relative tree kill on log dispenser density was highly significant ( = 0.34, corresponding effect size d≈ 0.98). In Sweden, with lower beetle populations, most attacks (99%) were found outside the experimental areas, with high attack rates (15 trees/ha) in a range of 15–30 m from treated groups, indicating an active inhibitory radius exceeding the previous estimates. The SDH as a functional aspect of biodiversity was tested by converting spruce monocultures into an artificial semiochemically mixed forests. The use of NHV provides the only non‐insecticidal method of direct protection of conifer forests. The demonstrated principle of protection is still too expensive for area‐wide use, but viable for high‐value areas (nature reserves). Further development of push–pull strategies or area‐wide applications may prove more cost efficient. In the long‐term, the only sustainable approach is a forest landscape of mixed habitats.     

The chemical composition of pine foliage in relation to the population dynamics of the pine beauty moth,Panolis flammea,in Scotland

Summary This paper reports part of a study to determine why damaging outbreaks of the pine beauty moth, Panolis flammea (D & S) (Lepidoptera: Noctuidae), in Scotland are frequent on lodgepole pine but do not occur on Scots pine, and why outbreaks on lodgepole pine are mainly confined to trees growing in deep unflushed peat. The elongation of shoots and the growth of needles of Scots pine occurred later in the season than did those of lodgepole pine. The foliage of Scots pine generally had a higher level of nitrogen, and consistently had a higher level of phosporus, but had a consistently lower level of tannins than that of lodgepole pine during the period when the larvae were feeding each year. The nitrogen content of the foliage of lodgepole pine growing in an iron pan soil was generally higher than that of lodgepole pine growing in deep peat during the same period but there were no general differences in the phosphorus or tannin contents of lodgepole pine in the 2 soil types. These findings suggest that Scots pine is a more suitable host plant than lodgepole pine and that the foliage of lodgepole pine growing in deep peat is not more suitable than lodgepole pine growing in an iron pan soil. On the basis of the chemical analyses used in this study, it is concluded that the abundance of pine beauty moth in Scotland is not strongly influenced by the nutritional suitability of its host plants.