Sex pheromone and visual trap interactions in mate location strategies and aggregation by host-alternating aphids in the field

Abstract. Field observations were made on the responses of males and gynoparae of three host-alternating aphid species, the blackberry-cereal aphid, Sitobion fragariae (Walker), the bird cherry-oat aphid, Rhopalosiphum padi (L.) and the damson-hop aphid, Phorodon humuli (Schrank) to species-specific sex pheromones released from transparent and coloured water traps.Pheromone traps caught significantly more males than did control traps without pheromone, whereas transparent, light green, yellow and orange traps caught most insects.Measurements of the distance over which sex pheromones function indicated that male P.humuli detect the pheromone 2–6 m from the source and can fly upwind to a source in wind speeds of 0.7 m s^-1.In all three species significantly more gynoparae were caught in pheromone traps than in control traps, suggesting that pheromone released by adult sexual females may assist late-flying gynoparae to locate a suitable host plant on which to deposit their progeny.The response is relatively stronger for males than gynoparae, but the pheromones appear to act as both sex and aggregation pheromones.     

Increased Parasitization of Aphids on Trap Plants Alongside Vials Releasing Synthetic Aphid Sex Pheromone and Effective Range of the Pheromone

Aphid-infested cereal trap plants were used to detect the effects of aphid sex pheromone components on aphid parasitoid activity in arable field margins. The presence of aphid sex pheromones significantly increased parasitization levels by aphid parasitoids on the plants. By placing plants alongside and at varying distances away from a pheromone-releasing vial, the technique was used to measure the distance over which a point source of aphid sex pheromone could increase parasitization levels. Pheromone-releasing vials significantly increased parasitization by the generalist parasitoid Praon volucre on plants adjacent to vials and on plants placed 20 cm away. When the distance between pheromone-releasing vials and aphid-infested plants was increased to 1 m, parasitization by P. volucre was increased only on the plant adjacent to the vial, whereas parasitization by the specialist parasitoid Aphidius rhopalosiphi was also increased on plants placed 1 m away. This indicates a possible difference between the parasitoids in their foraging behaviour in response to semiochemical cues during host selection. When the experiment was repeated with some trap plants placed 3 m away from the pheromone-releasing vial, parasitization was again concentrated on plants directly alongside the vial, but only P. volucre appeared to be active in the field at the time of this experiment, so the effect on A. rhopalosiphi could not be assessed. The results are encouraging for the prospects of using aphid sex pheromones to manipulate parasitoids in order to improve aphid population control.     

RELEVANCE OF PLANT VOLATILES TO SEX PHERO‐MONE IN LURING APHIDS IN THE FIELD1

Abstract Outdoor trials were made to test the responses of male aphids to pheromone lures in fields with different host‐plants, in order to know whether host‐plants would affect catches of males to pheromone lures. In peach orchard, males of three aphid species, i.e. Myzus persicae, Hyalopterus amygdali and Rhopalosiphum nymphaeae, were found in traps baited with aphid sex pheromone nepetalactone and nepetalactol. The most numerous numbers was M, persicae and it was also attracted by plant‐derived nepetalactone alone in peach orchard and cabbage garden. Schizaphis graminum males were caught in water traps in wheat field. In apple orchard, males of two aphid species, Aphis cifricola and Sappaphis sinipiricola were caught in significantly larger numbers in the pheromone traps than in the control traps. Field study indicated that the sex pheromone of H. amygduli comprises either one or both of nepetalactone and nepetalactol, and nepetalactone may be one component of sex pheromones of A cifricola and S sinipiricola Another field trial had shown that catches were increased if volatiles from a steam‐distilled extract of peach leaves were released simultaneously with nepetalactone. Elec‐troantennograms (EAGs) were recorded from males of M. persicae to volatiles of peach leaves and buds.     

Responses to aphid sex pheromones by the pea aphid parasitoids Aphidius ervi and Aphidius eadyi

Aphidius ervi and Aphidius eadyi, two parasitoids of the pea aphid Acyrthosiphon pisum, were attracted to components of the aphid sex pheromone in laboratory bioassays. Pre-test experience with host aphids in the presence of aphid sex pheromone did not affect the response of A. ervi to pheromone in a 4-way olfactometer, compared with that of naive parasitoids. Aphidius ervi females exposed only to the pheromone prior to testing did not respond in the olfactometer, suggesting habituation to the foraging cue by the parasitoid. In a wind tunnel, aphid sex pheromone increased the attraction of A. ervi to the plant-host complex (Vicia faba/A. pisum), suggesting an additive effect when two different foraging cues are present simultaneously.     

植物挥发性物质对蚜虫性信息素诱蚜效果的影响(英文)

本研究首先是在不同的寄主植物中利用蚜虫性信息素进行田间诱蚜实验。结果表明寄主植物影响性信息素田间诱蚜的种类和效果。在桃园 ,以蚜虫性信息素荆芥内酯和荆芥醇为性诱剂的水盆诱捕器 ,诱到 3种蚜虫的雄蚜 ,分别是桃蚜、桃粉大尾蚜和莲缢管蚜。其中 ,桃蚜占绝大多数 ,且还被性信息素的单一组分植物提取的荆芥内酯所吸引。麦田中诱到的雄蚜为麦二叉蚜。苹果园中诱到的雄蚜是绣线菊蚜和梨中华圆尾蚜 ,且性信息素诱捕器中的数目远多于对照诱捕器。据田间诱蚜实验结果推测 ,荆芥内酯和荆芥醇对桃粉大尾蚜有吸引作用 ,荆芥内酯可能是绣线菊蚜和梨中华圆尾蚜性信息素的一个组分。另外进行的田间实验表明寄主植物挥发性物质对蚜虫性信息素诱蚜效果有影响 ,当荆芥内酯诱捕器同时释放桃叶挥发物时 ,诱到的桃蚜雄蚜数量明显增加。触角电位记录实验也表明桃蚜雄蚜对桃叶挥发物和桃芽挥发物有反应。     

Sex pheromones in the cereal aphid parasitoidsPraon volucre andAphidius rhopalosiphi

Laboratory and field experiments provided evidence for the release of sex pheromones by virgin femalePraon volucre Haliday andAphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Braconidae, Aphidiinae). In Petri dish biosassays, rubber or vermiculite models treated with crude virgin female extracts were frequently approached by males and elicited rapid wing-fanning behaviour and copulation attempts. Delta-shaped water traps containing live virgin females caught large numbers of conspecific males when placed in winter wheat crops. Trapping slightly below crop height resulted in higher catches than trapping above the crop canopy.     

Intimate Rendezvous in a Tritrophic Context? Nothing but the Girls for Male Lysiphlebus testaceipes

In insects, mating often occurs after natal dispersal, and hence relies on a coevolved combination of sexual communication and movement allowing mate encounter. Volatile sex pheromones are widespread, generally emitted by females and triggering in‐flight orientation of conspecific males. In parasitoid wasps, unmated females can start laying unfertilized eggs via parthenogenesis so that host patches could serve as sites of rendezvous for mating. Males could therefore use cues associated with host patches to focus their search on females that have successfully found oviposition sites. We hypothesized that in parasitoids exploiting herbivorous hosts, sex pheromones, and herbivore‐induced plant volatiles (HIPV) should act in synergy, triggering male orientation toward ovipositing females. We tested this hypothesis with the aphid parasitoid Lysiphlebus testaceipes. Results from both field and laboratory experiments show that males are strongly attracted to virgin females, but that volatiles from aphid‐infested plants have no effect on male orientation, neither has a cue, nor in interaction with the female sex pheromone. The absence of synergy between sex pheromones and HIPV contrasts with results on other species and raises interesting questions on mating systems and sexual selection in parasitoid wasps.     

Efficiency of volatile baited sticky traps for the Tarnished Plant Bug (Lygus lineolaris) in strawberry fields

Insecticides have adverse effects on human health and the environment. Thus, the development of non-chemical replacement to manage insect pests is urgent. An alternative is to bait sticky traps with attractive insect sex pheromones or plant volatiles. In Quebec, the tarnished plant bug (Lygus lineolaris) is a major insect pest. We tested the efficiency of sex pheromones (mixture of hexyl butyrate (HB), (E)-2-hexenyl butyrate (E2HB) and (E)-4-oxo-2-hexenal (KA)) and sunflower (Helianthus annuus) volatiles (pinene, sabinene and phenylacetaldehyde) as sticky trap baits for the tarnished plant bug in strawberry fields of the Laurentians in Southern Québec, Canada. The pheromones decreased the number of tarnished plant bug caught in the traps compared to a control. The sunflower volatile did not have any effect on the number of individuals caught in the traps. Different Lygus species use HB, E2HB and KA in different ratios for sexual signals and alarm signals and for species recognition. GC-MS analysis of the sex pheromone bait revealed that the ratios between the three main compounds did not match the intended ratio for the L. lineolaris species. This mismatch probably explains our results. Individuals were not attracted to sunflower volatiles. Our results point to the difficulty of manufacturing and using sex pheromones as baits. Future work should assess the effect of several pheromone ratios.     

蚜虫性信息素

蚜虫属同翅目蚜总科,是重要的农作物害虫。蚜虫长年行孤雌生殖,在中、高纬度深秋时,产生性蚜,以卵越冬。雌性蚜分泌性信息素荆芥内酯(nepetalactone)和荆芥醇(nepetalactol)。该文综述了蚜虫性信息素的结构与组分、性腺的形态结构、性信息素释放及影响因素;性信息素对雌性母和天敌的引诱作用;性信息素在蚜虫种间隔离中的地位和作用以及蚜虫性信息素在蚜虫防治中的应用前景。     

Unexpected problem in aphid DNA barcoding by universal primers

DNA barcode (mitochondrial COI) sequences have allowed for species identification of aphids. In this study, we newly found a DNA barcoding problem in a part of the DNA sequences for Sitobion avenae. Five S. avenae individuals showed differences of, on average, 32.60% in the DNA sequences from other conspecific individuals, and a BLAST search revealed that the five sequences are similar to those of aphid parasitoids such as Aphidius, Ephedrus and Praon spp. (Hymenoptera: Braconidae). Based on these results, we concluded that the universal primers used in aphid DNA barcodes can amplify barcode sequences from parasitoid species within host aphids.     

Monitoring oriental fruit moth and codling moth (Lepidoptera: Tortricidae) with combinations of pheromones and kairomones

Experiments were conducted in North and South America during 2012–2013 to evaluate the use of lure combinations of sex pheromones (PH), host plant volatiles (HPVs) and food baits in traps to capture the oriental fruit moth, Grapholita molesta (Busck), and codling moth, Cydia pomonella (L.), in pome and stone fruit orchards treated with sex pheromones. The combination of the sex pheromone of both species (PH combo lure) significantly increased G. molesta and marginally decreased C. pomonella captures as compared with captures of each species with either of their sex pheromones alone. The addition of a HPV combination lure [(E,Z)‐2,4‐ethyl decadienoate plus (E)‐β‐ocimene] or acetic acid used alone or together did not significantly increase the catch of either species in traps with the PH combo lure. The Ajar trap baited with terpinyl acetate and brown sugar (TAS bait) caught significantly more G. molesta than the delta trap baited with PH combo plus acetic acid in California during 2012. The addition of a PH combo lure to an Ajar trap significantly increased catches of G. molesta compared to the use of the TAS bait or PH combo lure alone in 2013. Female G. molesta were caught in TAS‐baited Ajar traps at similar levels with or without the use of additional lures. Ajar traps baited with the TAS bait alone or with (E)‐β‐ocimene and/or PH combo lures caught significantly fewer C. pomonella than delta traps with sex pheromone alone. Ajar traps with 6.4‐mm screened flaps caught similar numbers of total and female G. molesta as similarly baited open Ajar traps, and with a significant reduction in the catch of non‐targets. Broader testing of HPV and PH combo lures for G. molesta in either delta or screened or open Ajar traps is warranted.     

Effects of honeydew and insecticide residues on the distribution of foraging aphid parasitoids under glasshouse and field conditions

The opposing effects of attraction to host-derived kairomones and repellency from the pyrethroid insecticide deltamethrin were investigated with aphid parasitoids from the genus Aphidius (Hymenoptera: Aphidiinae). The spatial distribution of female parasitoids was recorded in a series of experiments conducted in a small glasshouse containing wheat plants either infested with cereal aphids, Sitobion avenae (F.) (Homoptera: Aphididae), uninfested or treated with the recommended field concentration of deltamethrin. The number of parasitoids per plant were counted at 0.5 h, 1 h and then at one hourly intervals up to 8 h after release. Parasitoids showed a strong aggregation response to aphid-infested plants compared to adjacent uninfested plants. With the introduction of insecticidetreated plants around the aphid-infested plants, parasitoids showed a greater tendency to disperse away, resulting in fewer parasitoids on plants and significantly lower rates of aphid parasitism. The degree of aphid fall-off from plants was a good indicator of parasitoid foraging activity. In field studies, using sticky traps to measure the activity of parasitoids in plots sprayed with water, deltamethrin and/or an artificial honeydew solution, repellent properties were evident for up to 2 days after application. The attraction/arrestment stimuli associated with the honeydew solution were sufficient for parasitoids to continue searching insecticide-treated areas. The implications of these findings for parasitoids searching crops contaminated with aphid-derived kairomones and insecticides are discussed.     

Long-distance dispersal by a parasitoid (Anagrus delicatus,Mymaridae) and its host

Summary We demonstrate that an egg parasitoid, Anagrus delicatus (Mymaridae, Hymenoptera) and its host, Prokelesia marginata (Delphacidae, Homoptera) regularly disperse 1 km or more in a north Florida saltmarsh. Anagrus delicatus were caught on yellow sticky traps on offshore islets and oyster bars throughout the spring, summer, and fall, whereas P. marginata were caught during one pulse in the spring. Parasitism rates were higher on offshore islets than at mainland sites, even though egg densities were higher at the mainland sites. The majority of parasitoids caught offshore were females. Long-distance dispersal by A. delicatus may be a cause of inverse density-dependent or density-independent spatial patterns of parasitism and may represent a risk-spreading strategy.     

蚜虫性信息素对桃园蚜虫的引诱作用

将从荆芥Nepeta cataria L.中提取的纯度为96%的荆芥内酯和通过二异丁基铝还原提取的荆芥内酯得到的纯度为67%荆芥醇,配成浓度为5%的不同比例的己烷溶液,于1995年10月19～28日在北京大兴县南郊农场的桃园进行了引诱蚜虫的试验。各种比例的性信息素诱捕器均能引诱到桃蚜Myzus persicae (Sulzer)雄蚜、桃粉大尾蚜Hyaloptera amygdali Blanchard雄蚜以及少量的桃蚜产雌性母;荆芥醇和荆芥内酯的比例为1∶1时引诱桃蚜雄蚜的效果最好;单一组分的荆芥醇引诱桃粉大尾蚜雄蚜的效果最好。     

Attraction range of a sex pheromone trap for the damson‐hop aphid Phorodon humuli (Hemiptera: Aphididae)

The attraction range of olfactory response by winged female gynoparae (autumn migrants that give birth to oviparae, the sexual females) and male damson–hop aphids Phorodon humuli (Schrank) is investigated in field experiments over 2 years by analyzing the spatial patterns of catches in concentric circles of yellow‐painted traps (60 in total) around a central trap releasing the species' sex pheromone, (1RS,7S,7aS)‐nepetalactol. Males are more likely than females to be found in the central trap, with 65.6% of the 1824 males caught there compared with 11.2% of 1346 females. Both morphs are more numerous in traps axial with the mean wind direction and centred on the pheromone‐release trap than at other angles. Males are approximately five‐fold more numerous in traps downwind than at similar distances upwind of the pheromone, showing that its presence stimulates landing. For males, the estimated active space of the lure extends 6 m downwind. Catches of females are equally numerous up and downwind of the pheromone lure because females orienting on the axis of the pheromone source continue to respond to visual cues in their flight path if they overshoot the olfactory one. For females, the active space of a pheromone lure is less than 2 m downwind. It is unimportant for either morph whether the pheromone‐release trap is yellow or transparent. In these experiments, both morphs orient with, track and probably arrive in the pheromone source trap from at least 26 m, the distance to the nearest aphid‐infested hops.     

Application of synthetic sex pheromone for management of diamondback moth, Plutella xylostella, in cabbage

Over a 2-year period field trials were conducted to assess the potential to disrupt mating ofPlutella xylostella (L.) using a commercial rope formulation of a 70:30 mixture of (Z)-11-hexadecenal and (Z)-11-hexadecenyl acetate, two components of the sex pheromone of the female. Screened field cages were placed into blocks of cabbage which were either treated with the pheromone or left untreated. Different densities of P. xylostella pupae were placed into each cage and then larval and pupal counts were made of the subsequent generation. In addition, sentinel females at mating stations were placed in each cage to assess the influence of the pheromone on the ability of males to locate and mate with females. Likewise, we used pheromone traps to assess whether the pheromone treatment influenced the ability of males to locate a pheromone source. In both years larval and pupal populations, produced as a result of the original inoculation, did not differ between pheromone-treated and untreated fields. The effect of pheromone treatment on larval and pupal numbers did not change with changes in inoculated P. xylostella density, however, the density of P. xylostella released caused significant differences in the density of the subsequent generation. No significant differences were detected between the number of sentinel female adult P. xylostella that successfully mated in pheromone-treated fields compared with untreated fields. Significant differences in the numbers of male P. xylostella caught in pheromone-baited traps occurred between pheromone-treated and untreated fields in the first trial of 1993, and in the first trial in 1994 but not in the second trial. Such differences are often thought of as indications of mating disruption, although our other data presented in this study and reports from other studies indicate this is not always the case. Previous studies on mating disruption of P. xylostella in larger scale field tests have been performed but the results have been variable and often ambiguous. Overall, our results indicate that mating disruption of P. xylostella with the present technology does not appear to work even under the very controlled situations which we utilized to eliminate insect movement between plots.     

Influence of Host Pheromone on Egg Parasitism by Scelionid Wasps: Comparison of Phoretic and Nonphoretic Parasitoids

The kairomonal activity of the attractant pheromone for the spined soldier bug, Podisus maculiventris (Hemiptera: Pentatomidae), was investigated by exposing fresh pentatomid egg masses in field traps with or without synthetic pheromone. Predominantly two parasitoids were recovered from exposed eggs of P. maculiventris and Euschistus obscurus: Telenomus podisi Ashmead (a generalist pentatomid egg parasitoid) and Telenomus calvus Johnson (a phoretic specialist on Podisus eggs) (Hymenoptera: Scelionidae). The incidences of T. podisi from P. maculiventris and E. obscurus eggs placed in pheromone-baited and nonbaited traps were not significantly different, suggesting that this oophagous wasp does not use the spined soldier bug attractant pheromone as a kairomone. However, T. calvus was reared almost exclusively from egg masses of P. maculiventris placed inside pheromone-baited traps. These results suggest that T. calvus females orient to volatile chemicals emitted by spined soldier bug males as a searching strategy to find areas likely to contain host eggs, in addition to the previously discovered strategy of using the pheromone to guide their phoretic behavior. The data also indicate that T. calvus can distinguish between the egg masses of these pentatomid hosts at close range.     

Geographic variation in prey preference in bark beetle predators

Abstract 1. Bark beetles and their predators are useful systems for addressing questions concerning diet breadth and prey preference in arthropod natural enemies. These predators use bark beetle pheromones to locate their prey, and the response to different pheromones is a measure of prey preference. 2. Trapping experiments were conducted to examine geographic variation in the response to prey pheromones by two bark beetle predators, Thanasimus dubius and Temnochila virescens. The experiments used pheromones for several Dendroctonus and Ips prey species (frontalin, ipsdienol, and ipsenol) and manipulated visual cues involved in prey location (black vs. white traps). The study sites included regions where the frontalin‐emitter Dendroctonus frontalis was in outbreak vs. endemic or absent. 3. There was significant geographic variation in pheromone preference for T. dubius. This predator strongly preferred a pheromone (frontalin) associated with D. frontalis at outbreak sites, while preference was more even at endemic and absent sites. No geographic variation was found in the response by T. virescens. White traps caught fewer insects than black traps for both predators, suggesting that visual cues are also important in prey location. 4. The overall pattern for T. dubius is consistent with switching or optimal foraging theory, assuming D. frontalis is a higher quality prey than Ips. The two predator species partition the prey pheromones in areas where D. frontalis is abundant, possibly to minimise competition and intraguild predation.     

Prevalences of fungal pathogens and othernatural enemies of cereal aphids (Homoptera:Aphididae) in wheat under dryland and irrigatedconditions in South Africa

Surveys were conducted in the summer andwinter rainfall wheat producing regions of SouthAfrica in a first attempt to investigate theidentity and impact of entomopathogenic fungi withinthe cereal aphid complex. Wheat produced underdryland and irrigated conditions was surveyed duringthe 1996 and 1997 seasons. Six cereal aphid specieswere recorded of which the Russian wheat aphid, Diuraphis noxia, was the most abundantunder dryland conditions in the summer rainfallregion as opposed to the oat aphid, Rhopalosiphum padi, in the winter rainfallregion. Rose grain aphid, Metopolophiumdirhodum, was most prevalent underirrigated conditions in the summer rainfall region.Five species of entomopathogenic fungi were recordedincluding four entomophthorales and the hyphomycete,Beauveria bassiana. TheEntomophthorales included Pandora neoaphidis, Conidiobolus obscurus, C.thromboides, and Entomophthoraplanchoniana. Pandora neoaphidis wasthe most important etiological agent recorded fromD. noxia, with up to 50% mycosis recordedunder dryland conditions in the Bethlehem summerrainfall region. Similarly, P. neoaphidis wasthe most prevalent species within populations ofM. dirhodum. under irrigated conditions in theBergville/Winterton summer rainfall region (up to77% mycosis). However, mycoses of R. padi didnot exceed 1.7% in samples from these areas,suggesting that R. padi may be lesssusceptible to P. neoaphidis than M.dirhodum. Epizootics in populations of D.noxia under dryland conditions in both the winterand summer rainfall regions indicated a high levelof susceptibility to P. neoaphidis.Occurrences of hymenopterous parasitoids andpredators in populations of D. noxia were low,although a parasitism level of 25% was recorded inone small sample of R. padi collected from anirrigated field in the summer rainfall region.     

Effect of trap height and within-planting location on captures of cranberry fruitworm (Lepidoptera: Pyralidae) in highbush blueberries

Abstract 1 Winged traps baited with synthetic sex pheromone lures [(E,Z)‐8,10‐pentadecadien‐1‐ol and (E)‐9‐pentadecen‐1‐ol acetate] were evaluated for their effectiveness in monitoring cranberry fruitworm, Acrobasis vaccinii Riley, in highbush blueberry, Vaccinium corymbosum L., plantings. Trap effectiveness was compared at different heights within the bush canopy and different locations within plantings. 2 In our trap height study, three positions were evaluated: (i) at the top of bush canopy (15 cm below the uppermost branch); (ii) centrally within bush canopy (60 cm below the uppermost branch); and (iii) at the bottom of the bush, 20 cm above ground level. Traps placed 15 and 60 cm below the uppermost branch captured significantly more male moths compared with traps placed 20 cm above ground level at two organic sites. 3 In our trap location study, four treatments were evaluated based on trap location relative to adjacent woodlands: (i) in trees within 1 m of the woodland boundary; (ii) in blueberry bushes adjacent to woodlands, 15 m from the woodland boundary; (iii) in blueberry bushes in the centre of the planting, 75 m from the woodland boundary; and (iv) in blueberry bushes furthest away from woodlands, 150 m from the woodland boundary. Traps located within 1 m of woodland boundary captured significantly more male moths compared with traps located centrally (15 and 75 m) within plantings.