Non-host volatiles disrupt the response of the stenographer bark beetle, Ips sexdentatus (Coleoptera: Scolytidae), to pheromone-baited traps and maritime pine logs (original) (raw)
Related papers
Oikos, 2003
Zhang, Q.-H. and Schlyter, F. 2003. Redundancy, synergism, and active inhibitory range of non-host volatiles in reducing pheromone attraction in European spruce bark beetle Ips typographus.-Oikos 101: 299-310. Host and habitat selection in flight by conifer bark beetles is governed by inhibition of attraction by non-host volatiles (NHV), in addition to the well-known attraction to kairomones from host plants and to aggregation pheromones from conspecifics. Antennally-active NHV from angiosperm birch and aspen trees were field tested on the European spruce bark beetle, Ips typographus (L.), by pheromone baited traps in Sweden using release rates of NHV comparable to those from a non-host tree. Trap catches were significantly reduced by 50-70% by individual NHV: trans-conophthorin, 3-octanol and 1-octen-3-ol from non-host bark, 1-hexanol and (Z)-3-hexen-1ol from both leaves and bark and (E)-2-hexen-1-ol from leaves. Combined NHV signals in binary and ternary blends with the same overall release rates (ca 5 mg/day) showed both redundancy and synergism in their inhibitory effects. The redundancy occurred among individual green leaf alcohols (GLV-alcohols or C 6-alcohols), C 8-alcohols, and between these two groups, while trans-conophthorin and verbenone (Vn, from unsuitable host trees) showed significant synergistic effects between each other and with GLV-alcohols or C 8-alcohols. The coexistence of redundancy and synergism in non-host chemical signals may indicate different functional levels (non-host habitats, species, and unsuitable host trees) of these negative volatile signals in the host selection process of conifer bark beetles. We showed an active inhibitory range (AIR) of a NHV-blend plus Vn on a standard pheromone bait to be at least 2 m, by using a central pheromone trap and surrounding concentric barrier trap rings with radii of 1, 2, and 4 m. The influx of bark beetles flying across concentric rings within the AIR was reduced by 55-99%, depending on the distance to the central pipe trap. Our findings support the hypothesis that as mixed forests have greater semiochemical diversity than pure host stands; they disturb olfactory guided host choice, and may reduce the possibility of outbreaks of conifer-infesting bark beetles. The synergistic effects as well as the active inhibitory range found in this study also suggest that optimal combinations of these NHV and verbenone may have potential in protecting forests against I. typographus by reducing or stopping attacks on suitable host trees. Mixed stands with higher semio-chemical diversity disturb olfactory guided host choice and reduce the risk for outbreaks of specialist herbivores.. This 'semiochemical-diversity hypothesis' provides new support to the general 'stability-diversity hypothesis'.
PLoS ONE, 2014
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: dehydroconophthorin (DHC). Our results showed that 1-hexanol alone could replace the three-component GLV blend containing 1hexanol, (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 transconophthorin as a cost-efficient anti-attractant for forest protection against I. typographus.
Semiochemical Sabotage: Behavioral Chemicals for Protection of Western Conifers From Bark Beetles
The discovery and elucidation of volatile behavioral chemicals used by bark beetles to locate hosts and mates has revealed a rich potential for humans to sabotage beetle host-finding and reproduction. Here, we present a description of currently available semiochemical methods for use in monitoring and controlling bark beetle pests in western conifer forests. Delivery systems include hand-applied methods, such as semiochemical-releasing bubblecaps, pouches, and "puffers," as well as products that can be applied by aircraft such as semiochemical-releasing flakes. Descriptions of both attractant-based ("pull") and anti-attractant-based ("push") strategies are provided. Examples are provided for the major bark beetle pests in western North America, including the mountain pine beetle Dendroctonus ponderosae Hopkins), western pine beetle (Dendroctonus brevicomis LeConte), the Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins), the spruce beetle [Dendroctonus rufipennis (Kirby)], and the red turpentine beetle (Dendroctonus valens LeConte),. Logan, J.A. 1998. Silvicultural control of mountain pine beetle: prescriptions and the influence of microclimate. American Entomologist. 44: 166-177. Amman, G.D.; Thier, R.W.; Weatherby, J.C.; Rasmussen, L.A.; Munson, A.S. 1991. Optimum dosage of verbenone to reduce infestation of mountain pine beetle [Dendroctonus ponderosae] in lodgepole pine [Pinus contorta var. latifolia] stands of central Idaho. Res. Pap. INT-RP-446. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 6 p.
Field response of spruce bark beetle,Ips typographus, to aggregation pheromone candidates
Journal of Chemical Ecology, 1987
Six compounds previously identified from hindguts of unmated male Ips typographus (L.) during host colonization: 2-methyl-3-buten-2-ol (MB), cis-verbenol (cV), trans-verbenol (tV), myrtenol (Mt), trans-myrtanol (tM), and 2-phenylethanol (PE), were tested for their attractivity in the field with a subtractive method. The amounts of MB and cV released from a pipe trap were similar to those given off from the commercial bait Ipslure as well as that from a Norway spruce tree, Picea abies (L.) Karst., under mass attack. The blend of the compounds became nonattractive when either MB or cV was subtracted, while subtraction of any of the other four compounds bad no effect. Addition of ipsdienol (Id) to the blend did not significantly increase the attraction. In a second comparative test, the addition of three compounds as a group (tV + Mt + PE) to MB + cV again had no effect on the attraction, but the addition of Id increased the catch somewhat. Addition of host logs to a bait releasing MB + cV at a rate lower than in previous experiments did not influence the attraction to pipe traps. Sticky traps containing natural pheromone sources (50 males in a log), which released 1-5 rag/day of MB as determined by aerations with deuterated MB as internal standard, were less attractive than a synthetic source releasing similar amounts of MB.
In the search for compounds that contribute to the host or habitat discrimination, antennae of Ips typographus were screened for sensitivity to volatiles released by spruce trap-trees using gas chromatography linked to electroantennography. The antennally active compounds were determined using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection. Data show that I. typographus antennae respond to compounds emitted by the host. In total, 18 of antennally active compounds were detected: -4-ol, and verbenone. Unequivocal identification of all active minor compounds is provided and confirmed using synthetic standards. Compounds in minor quantities like 1,8-cineole, b-phellandrene, camphor, cis-pinocamphone, and trans-pinocamphone were more active than major spruce monoterpenes. We hypothesize that the minor spruce compounds may play so far unrecognized role in conveying information about host suitability for I. typographus.
Agricultural and Forest Entomology, 2012
1 Bark beetles are significant mortality agents of conifers. Four beetle species, the pine engraver Ips pini, the six-spined pine engraver Ips calligraphus sub. ponderosae, the southern pine beetle Dendroctonus frontalis, and the western pine beetle Dendroctonus brevicomis, cohabitate pines in Arizona. 2 A pheromone trapping study in ponderosa forests of Arizona determined the attraction of beetles to conspecific and heterospecific pheromone components in the presence and absence of host volatiles, and tested whether predators differ in their attraction to combinations of pheromone components and tree monoterpenes. 3 All four bark beetle species differed in their responses to heterospecific lures and monoterpenes. Ips calligraphus was the only species that increased in trap catches when heterospecific lures were added. Heterospecific lures did not inhibit the attraction of either Dendroctonus or Ips species. The replacement of myrcene with α-pinene increased the attraction of Dendroctonus, whereas the addition of α-pinene had mixed results for Ips. The prominent predators Temnochila chlorodia and Enoclerus lecontei were more attracted to the I. pini lure than the D. brevicomis lure, and the combination of the two lures with α-pinene was most attractive to both predator species. 4 Cross attraction and limited inhibition of bark beetles to heterospecific pheromones suggest that some of these species might use heterospecific compounds to increase successful location and colonization of trees. Predator responses to treatments suggest that tree volatiles are used to locate potential prey and predators are more responsive to Ips than to Dendroctonus pheromone components in Arizona.
Antennae of six sympatric bark and ambrosia beetles (Scolytidae), Dendroctonus valens LeConte, Gnathotrichus retusus (LeConte), Hylastes tenuis Eichhoff, Ips mexicanus (Hopkins), Ips plastographus maritimus Lanier, and Pseudohylesinus sericeus (Mannerheim), and two scolytid predators, Enoclerus sphegeus (F.) (Cleridae) and Lascontonus tuberculatus Kraus (Colydiidae), were analyzed by gas chromatographicelectroantennographic detection (GC-EAD) for their responses to synthetic Ips spp. pheromone components, and host and nonhost volatiles. The beetles emerged from cut logs of pitch canker-infected Monterey pine trees, Pinus radiata D. Don. There were significant disparities in EAD response patterns to the hemiterpene and monoterpene alcohol pheromone components that are typically produced by Ips spp. Antennae of I. p. maritimus responded strongly to (AE)-ipsdienol, (AE)-ipsenol, amitinol, and lanierone; antennae of I. mexicanus responded strongly to (1S,2S)-(-)-cis-verbenol, with weaker responses to (AE)-ipsdienol, (AE)-ipsenol, and amitinol; antennae of H. tenuis responded to (1S,2R)-(-)-trans-verbenol, with less pronounced responses to (-)-cis-verbenol and 2-methyl-3-buten-2-ol; and antennae of D. valens, G. retusus, and P. sericeus generally responded to all Ips spp. pheromone components except 2-methyl-3-buten-2-ol (D. valens and G. retusus) and E-myrcenol (G. retusus and P. sericeus). Ips mexicanus responded only to the (-)-enantiomers of ipsenol and ipsdienol, whereas I. p. maritimus responded to (-)-ipsenol, but to both the (+)-and (-)-enantiomers of ipsdienol. The antennae of the two predaceous insects (E. sphegeus and L. tuberculatus) responded to a range of the Ips spp. pheromone components. Host monoterpenes elicited no antennal responses from E. sphegeus, G. retusus, H. tenuis, and I. mexicanus, but several monoterpenes elicited various levels of responses from D. valens and I. p. maritimus antennae. Interestingly, antennae of female D. valens responded to (-), but not (+)-limonene. a-and b-Pinene elicited weak responses from L. tuberculatus antennae. EAD responses to selected nonhost volatiles were almost identical among the six scolytid species, with trans-conophthorin eliciting the strongest response in most cases, followed by three C 6alcohols and two C 8 -alcohols. The antennal responses by most of these species to linalool or geranylacetone were very weak; (E)-2-hexenal, (Z)-3-hexenyl acetate, and benzyl alcohol elicited almost no response. The response pattern of P. sericeus to nonhost volatiles differed slightly from the rest of the scolytids: a strong response to linalool, weaker response to the C 8 -alcohols. The two predaceous Coleoptera generally had weak, but detectable, responses to nonhost volatiles, except for a relatively strong response to trans-conophthorin by L. tuberculatus. No notable differences in EAD responses were observed between males and females of the two Ips spp. Our results provide an electrophysiological baseline for future efforts to identify attractive and repellent semiochemicals (aggregation pheromones, host kairomones, or nonhost interruptants) for this guild of scolytids and their key predators that are associated with moribund and pitch canker-infected P. radiata.
1 Host plant terpenes can influence attraction of conifer bark beetles to their aggregation pheromones: both synergistic and inhibitory compounds have been reported. However, we know little about how varying concentrations of individual monoterpenes affect responses. 2 We tested a gradient of ratios of a-pinene, the predominant monoterpene in host pines in the Great Lakes region of North America, to Ips pini's pheromone, racemic ipsdienol plus lanierone. 3 Ips pini demonstrated a parabolic response, in which low concentrations of a-pinene had no effect on attraction to its pheromone, intermediate concentrations were synergistic and high concentrations were inhibitory. These results suggest optimal release rates for population monitoring and suppression programmes. 4 Inhibition of bark beetle attraction to pheromones may be an important component of conifer defences. At terpene to pheromone ratios emulating emissions from trees actively responding to a first attack, arrival of flying beetles was low. This may constitute an additional defensive role of terpenes, which are also toxic to bark beetles at high concentrations. 5 Reduced attraction to a low ratio of a-pinene to pheromone, as occurs when colonization densities become high and the tree's resin is largely depleted, might reflect a mechanism for preventing excessive crowding. 6 Thanasimus dubius, the predominant predator of I. pini, was also attracted to ipsdienol plus lanierone, but its response differed from that of its prey. Attraction increased across all concentrations of a-pinene. This indicates that separate lures are needed to sample both predators and bark beetles effectively. It also provides an opportunity for maximizing pest removal while reducing adverse effects on beneficial species. This disparity further illustrates the complexity confronting natural enemies that track chemical signals to locate herbivores.
Agricultural and Forest Entomology, 2005
1 One proposed approach to improving biological control of bark beetles (Coleoptera: Scolytidae; alt. Curculionidae: Scolytinae) is to manipulate predator movement using semiochemicals. However, selective manipulation is impeded by attraction of both predators and pests to bark beetle pheromones. 2 The primary bark beetle affecting pine plantations in Wisconsin, U.S.A., is the pine engraver, Ips pini (Say). Other herbivores include Ips grandicollis (Eichhoff) and Dryophthorus americanus Bedel (Curculionidae). The predominant predators are the beetles Thanasimus dubius (Cleridae) and Platysoma cylindrica (Histeridae). 3 We conducted field assays using two enantiomeric ratios of ipsdienol, and frontalin plus a-pinene. Ipsdienol is the principal pheromone component of I. pini, and frontalin is produced by a number of Dendroctonus species. a-Pinene is a host monoterpene commonly incorporated into commercial frontalin lures. 4 Thanasimus dubius was attracted to frontalin plus a-pinene, and also to racemic ipsdienol. By contrast, I. pini was attracted to racemic ipsdienol, but showed no attraction to frontalin plus a-pinene. Platysoma cylindrica was attracted to 97%-(-)-ipsdienol and, to a lesser extent, racemic ipsdienol, but not to frontalin plus a-pinene. Ips grandicollis was attracted to frontalin plus a-pinene but not to ipsdienol. Dryophthorus americanus was attracted to both ipsdienol and frontalin plus a-pinene. 5 This ability to selectively attract the predator T. dubius without attracting the principal bark beetle in the system, I. pini, provides new opportunities for research into augmentative biological control and basic population dynamics. Moreover, the attraction of T. dubius, but not P. cylindrica, to frontalin plus a-pinene creates opportunities for selective manipulation of just one predator. 6 Patterns of attraction by predators and bark beetles to these compounds appear to reflect various degrees of geographical and host tree overlap with several pheromone-producing species.