Log colonization by Ips sexdentatus prevented by increasing host unsuitability signaled by verbenone

Sudden increments of breeding material after windstorms, forest fires, or inappropriate management practices help bark beetles such as Ips sexdentatus Boerner (Coleoptera: Curculionidae: Scolytinae) increase in numbers and colonize standing healthy pine trees. Preventing bark beetles from arriving to susceptible trees or logs may have great relevance for bark beetle management. Recent studies have reported inhibition of the aggregation response of I. sexdentatus using verbenone. Two field experiments were conducted to examine the effect of verbenone on the colonization pattern of this beetle. The first experiment tested the combined effect of trans‐conophthorin, a non‐host bark volatile with known repellent effect, and verbenone on Pinus sylvestris L. (Pinaceae) log piles of two sizes, but failed to protect them against I. sexdentatus attack when these two infochemicals were released at low rates. The results of this experiment suggested an interaction with the associated secondary bark beetle Orthotomicus erosus (Wollaston). A second experiment examined the response of I. sexdentatus and O. erosus to log piles that released verbenone at 0, 2, 10, or 40 mg day^?1. Although I. sexdentatus colonization of Pinus nigra Arnold logs was completely prevented at 40 mg day^?1, O. erosus could be found at all tested verbenone release rates. Besides verbenone, O. erosus colonization density and the height from which logs originated were the variables that best explained I. sexdentatus log colonization pattern. In addition, I. sexdentatus and O. erosus were rarely recorded colonizing the same log, and niche breadth analyses suggested that they excluded each other. The role of verbenone in the colonization process and its potential use in the prevention of population buildups of damaging bark beetles such as I. sexdentatus are discussed.     

The capacity of conophthorin to enhance the attraction of two Xylosandrus species (Coleoptera: Curculionidae: Scolytinae) to ethanol and the efficacy of verbenone as a deterrent

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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.     

Field response of non‐target beetles to Ips sexdentatus aggregation pheromone and pine volatiles

Although mass trapping cannot be a definitive control measure, it is one of the few ones available to contain the destruction of millions of cubic metres of conifer forests perpetrated every year worldwide by bark beetles. However, using bark beetle aggregation pheromones during both monitoring and control programs may negatively affect other saproxylic insects. The aim of this study was to describe the response of both Ips sexdentatus and its saproxylic beetle associates, especially predators, to traps baited with a commercial blend of I. sexdentatus aggregation pheromone. Furthermore, the usefulness of adding pine volatiles, such as (?)‐α‐pinene and ethanol, to the pheromone was discussed. The commercial blend proved to be attractive to I. sexdentatus adults, both when used alone and together with pine volatiles. Pheromone attractiveness, however, was lessened by the addition of the volatiles. The pheromone blend proved to be attractive to Thanasimus formicarius, as well as to other predator species. Overall, although during our study, traps baited only with (?)‐α‐pinene and ethanol attracted some predator specimens, I. sexdentatus pheromone traps were more attractive. Our study confirms that calendar differences in flight activity between the bark beetle and its predators are substantial; therefore, they should be taken into account when planning control measures. According to our data, the commercial blend of I. sexdentatus pheromone seems to be the most effective, among the baits used, in catching I. sexdentatus adults, while reducing the impact on T. formicarius.     

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.     

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.

     

Identification of further sex pheromone synergists in the codling moth, Cydia pomonella

A number of angiosperm nonhost volatiles (NHVs) and green leaf volatiles (GLVs) were tested alone and as supplements to the antiaggregation pheromone, verbenone, for their ability to disrupt attack by the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), on lodgepole pine, Pinus contorta Dougl. ex Loud. var. latifolia Engel. Preliminary experiments led to a refined NHV blend [benzyl alcohol, guaiacol, benzaldehyde, nonanal, salicylaldehyde, and conophthorin] and a refined GLV blend [(Z)-3-hexen-1-ol and (E)-2-hexen-1-ol]. In a 20-replicate experiment, NHV and GLV groups both singly, and verbenone alone, significantly reduced MPB mass attack on pheromone-baited trees and on trees within 5 m of the pheromone-baited trees. Both blends in combination with verbenone reduced the number of mass attacked, baited trees to three out of 20 compared to 20 out of 20 of the baited controls. Each binary combination was also effective at reducing mass attack. In these experiments, all tested repellents were released from devices stapled to trees at the same point as the pheromone bait, suggesting that the repellency could have been to a point source, rather than to the whole tree. Therefore, in two further experiments bands of release devices were wrapped around the treated trees and the pheromone bait was removed from the treated trees. In one experiment, when the aggregation pheromone bait was suspended between pairs of trees treated with the NHV blend plus GLV blend plus verbenone, only three out of 25 treated pairs had mass attack on at least one member of the pair. In the other 60-replicate experiment, with no pheromone baits present, attack occurred on 13 untreated and 11 banded trees, all in the path of a large advancing infestation. However, the mean attack density on the banded trees was significantly reduced to a level below the 40 attacks m^–2 of bark surface required to kill a healthy lodgepole pine. As a result of these experiments, operational trials are recommended.     

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.     

Disruption of trans‐pityol‐mediated attraction by racemic trans‐conophthorin in twig beetle Pityophthorus pubescens

Twig beetle Pityophthorus pubescens (Coleoptera: Curculionidae: Scolytinae) has been previously associated with the Fusarium circinatum (Hypocreales: Nectriaceae), the pathogen causing pitch canker disease, in P. radiata stands of the Basque Country (Northern Spain). Laboratory and field studies were conducted to evaluate the response of the insect to the racemic mixture of the spiroacetal trans‐7‐methyl‐1,6‐dioxaspiro[4.5]decane, also known as conophthorin. In walking bioassays, addition of 10 and 100 ng of racemic trans‐conophthorin to 1 ng of (±)‐trans‐pityol elicited a negative response in males, whereas females did not show any significant preference. Catches of males in attractant‐baited traps were strongly reduced by racemic trans‐conophthorin at all release rates tested (0.5, 1.0, 1.5 and 2.0 mg/day). In contrast, catches of females were not affected by any of the (±)‐trans‐conophthorin release rate.     

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.     

Monitoring the European pine sawfly with pheromone traps in maturing Scots pine stands

Abstract

• 1 During 1989–93, field studies were conducted in Finland to develop a method based on pheromone traps to monitor and forecast population levels of the European pine sawfly (Neodiprion sertifer Geoffr.) and tree defoliation.
• 2 Three traps per site were baited with 100 µg of the N. sertifer sex pheromone, the acetate ester of (2S,3S,7S)‐3,7‐dimethyl‐2‐pentadecanol (diprionol), in maturing pine stands in southern and central Finland. In addition, three different dosages (1, 10 and 100 µg) of the pheromone were tested in 1991–92.
• 3 The highest number of males was observed in traps baited with the highest dose. On average, there was a 10‐fold increase in trap catch between lure doses.
• 4 Density of overwintering eggs was used to evaluate the effectiveness of pheromone traps in predicting sawfly populations. The proportion of healthy overwintering eggs was determined each year. A model based on the number of current shoots on sample trees, diameter at breast height and tree height was formulated to estimate eggs per hectare.
• 5 Linear regression analysis produced high coefficients of determination between number of males in traps and density of total eggs in the subsequent generation, when populations were at peak densities. The relationships were not significant for low population densities. The results indicate a risk of moderate defoliation when the seasonal trap catch is 800–1000 males per trap or higher.

     

Factors affecting captures of male citrus leafminer, Phyllocnistis citrella Stainton, in pheromone-baited traps

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is an important world‐wide pest of citrus. Larval mining within leaf flush impacts yield and predisposes trees to infection by citrus canker, Xanthomonas axonopodis pv. citri. The present series of studies sought to identify factors affecting male P. citrella catch in pheromone‐baited traps with the intent of developing effective monitoring. A commercially available pheromone lure (Citralure, ISCA Technologies, Riverside, CA, USA) was highly effective in attracting male P. citrella to traps. Pherocon VI Delta (Trécé Inc., Adair, OK, USA) traps baited with a Citralure captured more male P. citrella than identically baited Pherocon IC Wing traps (Trécé Inc.). The superiority of the Delta‐style trap was found to be due to a 3 cm long closing latch that likely prevents males from flying directly through the trap without capture. Within canopies of mature citrus trees (approximately 3.5 m high), traps at mid‐canopy height (2.0 m) captured more males than traps placed higher (3.5 m) or lower (0.6 m). On the canopy perimeter and in between canopies, traps near ground level (0.6 m height) captured more males than traps at 2.0 and 3.5 m heights. Male catch was greater within the tree canopy or on the canopy perimeter than 2.0 away from the canopy. Traps deployed in trees on the edge of groves captured more males than traps placed 120 and 240 m away from the grove edge and within the grove interior. In non‐pheromone‐treated grove plots, the optimal dosage for catching males was between 0.1 and 1.0 mg of the 3 : 1 blend of (Z,Z,E)‐7,11,13‐hexadecatrienal and (Z,Z)‐7,11‐hexadecadienal; however, in pheromone‐treated plots a higher 10.0 mg dosage lure was most effective. Male catch in pheromone‐baited traps exhibited a diel rhythm with most males captured during scotophase (22:00–23:00 h) and no males captured during photophase.     

Mass‐trapping trials for the control of pine processionary moth in a pine woodland recreational area

The pine processionary moth, Thaumetopoea pityocampa, causes serious defoliation to Cedrus, Pinus and Pseudotsuga trees, as well as health problems in humans, pets and farm animals due to their urticating hairs. Environmentally friendly strategies for the management of T. pityocampa include: removal of egg batches, removal of nests, trapping of migrant larvae, spraying microbial or Insect Growth Regulator (IGR) insecticides and biocontrol, as well as pheromone‐based adult trapping and mating‐disruption. In the present paper, results on innovative technology for the control of T. pityocampa infestation using pheromone mass‐trapping are reported. Two 1‐ha plots were identified in the study area (central‐south Italy), a pine woodland recreational site growing Pinus halepensis. In the experimental plot (MT‐plot), 10 G‐traps (funnel trap type) baited with (Z)‐13‐hexadecen‐11‐ynyl acetate sex pheromone component were placed for mass‐trapping of adults; the other plot was used as a control‐plot (C‐plot). The T. pityocampa population was monitored using the two central traps in the MT‐plot and two traps positioned in the C‐plot. In addition, the winter nests made by T. pityocampa larvae overwintering on pine trees were counted. After 2 years of mass‐trapping, the number of adults trapped by the monitoring pheromone traps decreased in the MT‐plot, but not in the C‐plot, whereas the number of nests decreased in both plots. Statistical results highlighted significant differences in trap catches between the two plots but not between years. In the case of nests, differences among plots were not significant before the mass‐trapping, but significant after 1‐year treatment. According to our results, the mass‐trapping technique is able to reduce T. pityocampa infestations. This pheromone method can be applied in combination with other control systems in the context of integrated pest management in recreational areas.     

Acetophenone superior to verbenone for reducing attraction of western pine beetle Dendroctonus brevicomis to its aggregation pheromone

1 The western pine beetle Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae) is one of the most damaging insect pests of ponderosa pines Pinus ponderosa Douglas ex P. & C. Lawson in Western U.S.A. We compared the effect of verbenone, a well known bark beetle anti‐aggregation pheromone, with that of acetophenone on the attraction of D. brevicomis to its aggregation pheromone in a ponderosa pine forest in northern California. We tested the D. brevicomis aggregation pheromone alone and with three different release ratios of the aggregation pheromone (attractant) to verbenone or acetophenone (1 : 1, 1 : 2 and 1 : 5). 2 All treatments containing acetophenone or verbenone resulted in a significant reduction in the catch of D. brevicomis relative to the aggregation pheromone alone. When beetle responses to the three verbenone or three acetophenone treatments were pooled, the pooled verbenone treatment caught more D. brevicomis than the pooled acetophenone treatment. 3 There was no significant difference in the number of D. brevicomis caught among the three release rates of verbenone. By contrast, the 1 : 2 attractant : acetophenone ratio attracted significantly more D. brevicomis than the traps with the 1 : 5 attractant : acetophenone ratio. 4 Attraction of a major predator, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), to the aggregation pheromone of D. brevicomis was reduced by verbenone, but not by acetophenone. Moreover, the T. chlorodia : D. brevicomis ratio for the pooled acetophenone treatment was 1.7‐fold greater than that for the attractant alone and two‐fold greater than the ratio for the pooled verbenone treatment, suggesting that acetophenone would not disrupt populations of this natural enemy. The importance of anti‐attractants in the biology of D. brevicomis and other bark beetles is discussed.     

Integrating repellent and attractant semiochemicals into a push–pull strategy for ambrosia beetles (Coleoptera: Curculionidae)

Non‐native ambrosia beetles (Coleoptera: Curculionidae), especially Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky) and Xylosandrus germanus (Blandford), are destructive wood‐boring pests of trees in ornamental nurseries and tree fruit orchards. Previous studies have demonstrated the adults are repelled by verbenone and strongly attracted to ethanol. We tested a “push–pull” semiochemical strategy in Ohio, Virginia and Mississippi using verbenone emitters to “push” beetles away from vulnerable trees and ethanol lures to “pull” them into annihilative traps. Container‐grown trees were flood‐stressed to induce ambrosia beetle attacks and then deployed in the presence or absence of verbenone emitters and a perimeter of ethanol‐baited interception traps to achieve the following treatment combinations: (a) untreated control, (b) verbenone only, (c) ethanol only, and (d) verbenone plus ethanol. Verbenone and ethanol did not interact to reduce attacks on the flooded trees, nor did verbenone alone reduce attacks. The ethanol‐baited traps intercepted enough beetles to reduce attacks on trees deployed in Virginia and Mississippi in 2016, but not in 2017, or in Ohio in 2016. Xylosandrus germanus, X. crassiusculus and both Hypothenemus dissimilis Zimmermann and X. crassiusculus were among the predominant species collected in ethanol‐baited traps deployed in Ohio, Virginia and Mississippi, respectively. Xylosandrus germanus and X. crassiusculus were also the predominant species dissected from trees deployed in Ohio and Virginia, respectively. While the ethanol‐baited traps showed promise for helping to protect trees by intercepting ambrosia beetles, the repellent “push” component (i.e., verbenone) and attractant “pull” component (i.e., ethanol) will need to be further optimized in order to implement a “push–pull” semiochemical strategy.     

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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Efficacy of the pheromone (3Z)‐lactone and the host kairomone (3Z)‐hexenol at detecting early infestation of the emerald ash borer,Agrilus planipennis

The invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp., in its introduced range in North America. Field studies were conducted to quantify the efficacy of traps baited with kairomone and pheromone lures for early detection of A. planipennis infestation. A trapping experiment demonstrated that green traps baited with the kairomone (3Z)‐hexenol detected at least one adult A. planipennis in 55.3% of plots with ‘nil to low’‐density infestations and in 100% of plots with ‘moderate to high’‐density A. planipennis infestations. Mean trap captures increased significantly with increasing infestation density. In terms of the optimal number of traps per plot, when one (3Z)‐hexenol‐baited trap was placed per plot, the trap detected populations in 62% of the plots with ‘low to moderate’‐density infestations through branch sampling. Detectability was increased to 82% when two traps were placed per plot. Finally, addition of female‐produced (3Z)‐lactone pheromone to traps significantly increased detection rates at both the trap and plot level, as compared with traps baited with the host volatile, (3Z)‐hexenol, alone (88 vs. 60%, respectively). Our results are the first to demonstrate the efficacy of baited green sticky traps for detecting low‐density A. planipennis infestations, particularly when the (3Z)‐lactone pheromone is used. This combination is therefore recommended for development of early‐detection protocols against A. planipennis.     

Monitoring oriental fruit moth (Lepidoptera: Tortricidae) with the Ajar bait trap in orchards under mating disruption

Studies in Oregon, California, Pennsylvania and Italy evaluated the relative performance of the Ajar trap compared with several other traps for the capture of Grapholita molesta (Busck), in pome and stone fruit orchards treated with sex pheromone dispensers for mating disruption. The Ajar is a delta‐shaped trap with a screened jar filled with an aqueous terpinyl acetate plus brown sugar bait solution (TAS) that opens inside the trap and is surrounded by a sticky liner. The TAS‐baited Ajar trap was evaluated with and without the addition of a sex pheromone lure and compared with a delta trap baited with a sex pheromone lure and a bucket trap filled with the TAS bait. Although the Ajar trap had a 90% lower evaporation of the TAS bait than the bucket trap, both of them caught similar numbers in the majority of the field tests of both sexes of G. molesta. The addition of the sex pheromone lure did not increase moth catches by the TAS‐baited Ajar trap. The TAS‐baited Ajar trap caught significantly greater numbers of moths than the sex pheromone‐baited delta trap in 18 of the 20 orchards. Few hymenopterans were caught in orange TAS‐baited Ajar traps, but the catch of flies and other moths relative to the target pest remained high. Flight tunnel and field tests evaluated the effect of several screen designs on the catches of G. molesta and non‐target species. All exclusion devices significantly reduced the catch of larger moths. However, designs that did not reduce the catch of male G. molesta did not reduce the catch of muscid flies. Exclusion devices with openings <7.0 mm significantly reduced the catch of female G. molesta. The addition of (E)‐β‐farnesene, (E)‐β‐ocimene or butyl hexanoate septa lures to TAS‐baited Ajar traps significantly increased total moth catch. The addition of (E)‐β‐ocimene also significantly increased female moth catch.     

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.