Host-finding Kairomone Research Articles

Is there any evidence that aphid alarm pheromones work as prey and host finding kairomones for natural enemies?

1. The aphid alarm pheromone (E)‐β‐farnesene (EBF) is often considered to be used by natural enemies as a prey/host finding kairomone. However, studies show opposing results, some appear to confirm an attraction of aphid natural enemies by EBF whereas others do not provide any evidence for the kairomone function of EBF.2. To clarify if aphid natural enemies are attracted by the amounts of EBF naturally emitted by aphids, the existing literature was reviewed about EBF attractiveness to aphid natural enemies with consideration of the amounts of EBF used in the studies.3. Thirty‐one publications that investigated the ability of EBF, aphid cornicle secretion, and attacked aphids, to attract aphid natural enemies were found. Several studies showed an attraction by EBF, but these used much higher amounts of EBF than usually emitted by aphids during a predator attack. Studies investigating EBF amounts similar to what is emitted by aphids are rare and failed to show attraction. Only two studies document an attraction of natural enemies by attacked aphids.4. As EBF is emitted in very low amounts, not very stable, and only present after an attack, we suggest that aphid‐derived EBF is not a suitable kairomone for most natural enemy species, especially when they are able to use alternative cues. As EBF, amongst other volatiles, is also emitted by herbivore‐induced plants, we propose that natural enemies might use plant‐derived EBF as a synomone to identify aphid‐infested plants via an altered plant volatile bouquet.

A Chemical Lure for Stink Bugs (Hemiptera: Pentatomidae) is used as a Kairomone byAstata occidentalis(Hymenoptera: Sphecidae)

Abstract We tested lures in Washington and Georgia containing methyl (E,E,Z)-2,4,6-decatrienoate and/or methyl (E,Z)-2,4-decadienoate for capturing stink bug species (Hemiptera: Pentatomidae). In both states, we consistently captured adult females of the digger wasp Astata occidentalis Cresson (Hymenoptera: Sphecidae) in traps with lures that contained methyl (E,E,Z)-2,4,6-decatrienoate but not in traps with lures that contained only methyl (E,Z)-2,4-decadienoate. Astata occidentalis is a predator of pentatomid stink bugs (Hemiptera) and apparently uses methyl (E,E,Z)-2,4,6-decatrienoate as a host-finding kairomone. Methyl (E,E,Z)-2,4,6-decatrienoate is an aggregation pheromone of Plauti stali Scott (Hemiptera: Pentatomidae) that is also attractive to, and used for monitoring, the exotic brown marmorated stink bug, Halyomorpha halys Stal (Hemiptera: Pentatomidae). Wasps were captured from Jul through Sep with peak response in Aug in Washington. In Georgia, wasp capture was highest as soon as traps were de...

Response of a parasitoid fly, Gymnosoma rotundatum (Linnaeus) (Diptera: Tachinidae) to the aggregation pheromone of Plautia stali Scott (Hemiptera: Pentatomidae) and its parasitism of hosts under field conditions

We studied the attraction of a tachinid fly, Gymnosoma rotundatum (Linnaeus) to the male-produced aggregation pheromone of the brown-winged green bug, Plautia stali Scott, its parasitism on the bug, and its seasonal occurrence in the field. The tachinid fly was continuously attracted to the aggregation pheromone from spring to autumn and utilized the bugs as hosts. Our field experiment to clarify the effect of the pheromone on parasitism demonstrated that parasitism occurred only in female bugs baited with synthetic aggregation pheromone and did not occur in females without the pheromone. The parasitoid flies therefore appeared to use the bug’s pheromone as a host-finding kairomone. The pheromone attracted not only female flies but also males. Male flies may increase their chance of encountering pheromone-attracted females by waiting near pheromone sources. The tachinid develops multiple generations in active hosts from spring to autumn and overwinters in dormant hosts. Thus, G. rotundatum seems to be highly adapted to using P. stali as its host, and it is a potentially important biological control agent of P. stali populations in the field.

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.

Parasitoids of the Consperse Stink Bug (Hemiptera: Pentatomidae) in North Central Washington and Attractiveness of a Host-Produced Pheromone Component

The parasitoid complex of the consperse stink bug, Euschistus conspersus Uhler, was investigated in a series of field experiments conducted in native vegetation surrounding commercial apple orchards in the state of Washington. Rearing of parasitoids from adult E. conspersus confirmed the presence of two tachinid species, Gymnosoma filiola Loew and Gymnoclytia occidentalis Townsend. Three species of scelionids were reared from fresh egg masses placed on mullein plants (Verbascum thapsus L.) with Trissolcus utahensis (Ashmead) being the most common species. Though some parasitism was recorded in all study sites by both tachinids and scelionids, overall levels of parasitism were low (<10%). Predation comprised the major source of egg mortality in the field. Bucket traps baited with the male-produced aggregation pheromone component, methyl (2E,4Z)-decadienoate, captured significantly more G. occidentalis than unbaited controls, suggesting that it may use this compound as a host-finding kairomone. A test comparing E. conspersus egg masses placed on baited vs. unbaited V. thapsus revealed no differences in the rate of parasitism by scelionid parasitoids.

Kairomone strains of Euclytiaflava (Townsend), a parasitoid of stink bugs.

Tachinid flies commonly use the pheromones and allomones of stink bugs (Pentatomidae) as host-finding kairomones. Pheromone-baited traps for predaceous (Podisus spp.) and phytophagous (Euschistus spp.) pentatomids were used to obtain tachinid parasitoids in order to study the semiochemical relationships between these parasitic flies and their stink bug hosts. Gas chromatography-electroantennogram detector (GC-EAD) experiments and field tests were conducted to determine if pheromone strains of the tachinids, Euclytia flava and Hemyda aurata, occur in nature and to determine if the EAD-active compound, (E)-2-octenal (a common allomone compound of Heteroptera), affects attraction of tachinid parasitoids to synthetic Podisus pheromones. Addition of (E)-2-octenal to Podisus spp. synthetic pheromones in field traps tended to suppress attraction of the bugs, whereas (E)-2-octenal decreased, did not affect, or increased pheromonal attraction of tachinid parasitoids depending on the host species pheromone being tested and the habitat type in which the traps were deployed. Evidence from GC-EAD experiments of E. flava associated with different stink bug hosts suggested that kairomone-strains of this tachinid parasitoid coexist naturally. The significance of cryptic kairomone strains of parasitoids for classical biological control is discussed, and the mechanisms whereby parasitoids evolve kairomonally mediated host-shifts is considered.

Kairomonal response by four Monochamus species (Coleoptera: Cerambycidae) to bark beetle pheromones.

We investigated the hypothesis that wood-boring beetles in the genus Monochamus (Cerambycidae) utilize pheromones of sympatric bark beetles as host-finding kairomones. All nine bark beetle pheromones tested electrophysiologically were antenally active for both sexes of M. scutellatus, M. clamator, and M. obtusus from British Columbia. When field-tested with multiple-funnel traps (British Columbia) or cross-vane traps (Ontario), a blend composed of frontalin, ipsdienol, ipsenol, and MCH, in combination with a blend of host volatiles attracted significant numbers of M. clamator, M. obtusus, M. notatus, and M. scutellatus to baited traps. Traps baited with host volatiles in combination with a second blend composed of endo-brevicomin, exo-brevicomin, cis-verbenol, trans-verbenol, and verbenone caught no more beetles than unbaited traps or traps baited with the host blend alone. In British Columbia, traps baited with the first blend alone or both blends together captured more M. scutellatus and M. clamator than unbaited traps, demonstrating a response to bark beetle pheromones in the absence of host volatiles. These results suggest that Monochamus spp. are minimizing foraging costs by using the pheromones of sympatric bark beetles as kairomones.

Pheromones and colonization: reassessment of the milkweed bug migration model (Heteroptera: Lygaeidae: Lygaeinae)

Research on insect migration has justifiably emphasized females – the so-called “oogenesis-flight syndrome”– since it is the females that place the eggs into new habitats. The large and small milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii, respectively, have featured prominently in studies of insect migration and sequestration of host plant toxins for chemical defense. Here we report that males of these species, and males of another well-studied lygaeine (Neacoryphus bicrucis), produce pheromones in glands usually considered to serve only a defensive role in Heteroptera (the metathoracic scent glands), and that these pheromones are exploited by a tachinid parasitoid as a host-finding kairomone. The pheromones are mixtures of C6 and C8 saturated and unsaturated esters reminiscent of lepidopteran pheromones, and the key compound of the O. fasciatus pheromone has now been correctly identified as (E)-2,7-octadienyl acetate. It is proposed that the concept of the oogenesis-flight syndrome for these kinds of insects should accommodate the role of males in the migration process. The hypothesis is presented that male-produced pheromones play a significant role in guiding colonization of new habitats in many heteropteran species. In addition, data are presented suggesting that there is a trade-off between the amount of pheromone produced by colonizing males and the host breadth of the species.

Cross-Attraction of Carpophilus humeralis to Pheromone Components of Other Carpophilus Species

The pineapple beetle, Carpophilus humeralis, is known from field tests to be more attracted to baits containing the pheromone blends of other Carpophilus species and food odors than to food odors alone, but a pheromone is not yet known for C. humeralis. Wind-tunnel bioassays were used to determine specifically which of the Carpophilus pheromone components were the most attractive for C. humeralis. Nine tetraene and triene components normally used in field studies, plus eight additional male-specific compounds from other Carpophilus species, and one additional analog, were used in these experiments. At the 10-ng level, 15 of 18 compounds tested with a food-related coattractant (propyl acetate) were more attractive for C. humeralis than the coattractant alone. With decreasing doses (1, 0.1, and 0.01 ng) the number of attractive compounds declined. Only one compound, (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene (1), had significant attraction for C. humeralis at 0.01 ng, close to the lower threshold level of pheromone attraction for other Carpophilus species. Responses to mixtures of compounds were explored. For example, 1 was synergistic with 4-ethyl-2-methoxyphenol (E), 2,5-diisopropylpyrazine (D), and 2-phenylethanol (P), which are known attractants for C. humeralis; a mixture of 1 plus E, D, and P was 20 times more attractive than 1 alone and five times more than E, D, plus P. The specificity of C. humeralis for certain tetraenes was similar to that exhibited by C. hemipterus, while the specificity for trienes was similar to that of C. freemani. The behavior of C. humeralis to these pheromone components suggests that it may have a pheromone like that of other Carpophilus species or that it could possibly use these compounds as host finding kairomones.

Upwind flight of Prostephanus truncatus is mediated by aggregation pheromone but not food volatiles

Flight bioassays were carried out to investigate the response of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) to maize volatiles in comparison to the male-produced aggregation pheromone. Upwind attraction of flying P. truncatus is mediated by the male-produced aggregation pheromone. In contrast, beetles showed no response to maize grains or volatiles, and no interactions between aggregation pheromone and maize volatiles were recorded. This absence of upwind flight to food volatiles, or any synergism between pheromone and food volatiles suggests that the male-produced aggregation pheromone is the only known long-range semiochemical used by P. truncatus for dispersal and host-selection. These results are in contrast with those on several other stored-product species, and suggest that P. truncatus may not use maize volatiles as long-range host finding kairomones in nature. We propose a hypothesis for the process of dispersal and host colonisation by P. truncatus.

Aphid alarm pheromone (E)-?-farnesene: A host finding kairomone for the aphid primary parasitoidAphidius uzbekistanicus (Hymenoptera: Aphidiinae)

The present study aimed to test the possible function of the aphid alarm pheromone (E)-β-farnesene (EBF) as a host finding kairomone for aphid primary parasitoids. Extracts of volatile emissions of undisturbed aphids and of aphids under parasitoid attack were obtained by air entrainment. Extracts of cornicle secretions were gained by disturbing aphids and taking their secretions into solution. Extracts were compared by gas chromatography. Only air entrainments of aphids under attack and solvent extracts of cornicle secretions contained the alarm pheromone. In Y-tube olfactometer bioassays, femaleA. uzbekistanicus were attracted to aphid groups under attack of parasitoids, presumably by released EBF. High concentrations of synthetic EBF (1.4 µg to 5.7 µg) also attractedA. uzbekistanicus females. Females with oviposition experience reacted more readily to lower concentrations of EBF than females without experience. In experiments designed as Petri-dish bioassays, the test animals could contact filter paper discs that were treated with solutions containing EBF. Behavioural effects like antennation or stinging attack were not observed. With computer video analysis of parasitoid movements, some effects onA. uzbekistanicus behaviour were detected, again indicating attraction to EBF. As the volatile aphid alarm pheromone attractedA. uzbekistanicus females, it can be concluded that this chemical stimulus acts as a host finding kairomone for this parasitoid species. However, its effect over long distances seems to be limited due to the relatively high concentrations required for reactions. Of two other parasitoid species examined (P. volucre andL. testaceipes) onlyP. volucre was also significantly attracted to the volatile EBF in the Y-tube olfactometer.

Testing the “new associations” biological control concept with a tachinid parasitoid (Euclytia flava)

Males of the spined soldier bug,Podisus maculiventris (Heteroptera: Pentatomidae), produce an attractant pheromone that is exploited as a host-finding kairomone by a complex of parasitic species. The capability to catch hundreds of a generalist tachinid fly parasitoid,Euclytia flava, alive in traps baited with the pheromone ofP. maculiventris provided an opportunity to test the premise of the "new associations" biological control concept. The hypothesis that host species newly associated with a parasitoid are maladapted relative to native-native associations was tested by givingE. flava females a choice between native and exotic stink bugs (Heteroptera: Pentatomidae). WildE. flava females preferred to oviposit on exotic pentatomid species rather than indigenous, known host species, both in field traps baited with the pheromone of a native host and in the laboratory. Data presented here demonstrate that an invader may be vulnerable to native parasitoids in one aspect of the parasitism process (acceptance), yet go unrecognized as a potential host.

ATTRACTION OF LASCONOTUS INTRICATUS KRAUS. (COLEOPTERA: COLYDIIDAE) TO THE AGGREGATION PHEROMONE OF THE FOUR-EYED SPRUCE BARK BEETLE, POLYGRAPHUS RUFIPENNIS (KIRBY) (COLEOPTERA: SCOLYTIDAE)

AbstractThe cylindrical bark beetle, Lasconotus intricatus Kraus., is attracted to multiple-funnel traps baited either with black spruce logs infested with male four-eyed spruce bark beetles, Polygraphus rufipennis (Kirby), or the male-produced aggregation pheromone, 3-methyl-3-buten-1-ol. The addition of the host terpenes, bornyl acetate and β-pinene, to 3-methyl-3-buten-1-ol reduced the attraction of L. intricatus. 3-Carene, myrcene, and α-pinene appeared to have a partial inhibitory effect. Catches in spring and summer disclosed a high degree of temporal coincidence between the two species. We hypothesize that L. intricatus utilizes the aggregation pheromone of P. rufipennis as a host-finding kairomone.

Identification and Attractiveness of a Major Pheromone Component for Nearctic Euschistus spp. Stink Bugs (Heteroptera: Pentatomidae)

Methyl (2 E ,4 Z )-decadienoate was isolated and identified as the major male-specific volatile of Euschistus conspersus, E. tristigmus, E. servus, E. politus , and E. ictericus . In a sixth species, E. obscurus , this ester is a relatively minor male-specific component, with the major component being tentatively identified as methyl 2,6-dimethyltetradecanoate. Females, males, and nymphs of E. conspersus, E. tristigmus, E. servus , and E. politus were significantly attracted to methyl (2 E ,4 Z )-decadienoate in field tests conducted in California and Maryland. Tests in Maryland also demonstrated that parasitic tachinid flies use the Euschistus unsaturated methyl-ester as a host-finding kairomone. It is not yet clear what role minor volatile components of Euschistus play in reproductive isolation.

Attraction ofOryzaephilus surinamensis (L.) andOryzaephilus mercator (Fauvel) (Coleoptera: Cucujidae) to some common volatiles of food

Responses by adultOryzaephilus surinamensis (L.) andOryzaephilus mercator (Fauvel) to various food volatiles were assessed by means of a two-choice, pitfall olfactometer. The individual experimental stimuli, all potential products of lipid oxidation, had a range of attractive doses of ≤ 1000-fold over the test dose ranges of 0.001-100 gmg, or 0.01-1000 gmg. Of 13 aliphatic C3-C14 aldehydes and benzaldehyde tested forOryzaephilus spp., 10 C3-C10 aliphatic aldehydes and benzaldehyde showed some attractiveness for both species. ForO. mercator, nonanal had the lowest lower threshold for positive response at 0.01 μg. The addition of small amounts of nonanal or of a 1∶1∶1 mixture of hexanal, octanal, and nonanal to small amounts of cucujolide aggregation pheromones enhanced response by mixed-sexO. mercator to the pheromones. Eleven aliphatic C2-C9 free fatty acids showed some attractiveness for bothOryzaephilus spp. Isovaleric acid and valeric acid had the lowest lower thresholds for positive response at 0.1 μg forO. mercator andO. surinamensis, respectively. Four olefinic oat volatiles were found to possess various degrees of attractiveness for bothOryzaephilus spp. The data suggest that food volatiles in this study might be used byOryzaephilus spp. as host-finding kairomones in nature.