Possible coexistence of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae) in the biological control of Lipaphis erysimi (Homoptera: Aphididae)

To study the interactions between the aphidophagous predator Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and the specialist aphid parasitoid Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae) in the biological control of mustard aphid, Lipaphis erysimi (Homoptera: Aphididae), the prey discrimination by H. axyridis among unparasitized, non-mummified parasitized and mummified aphids was examined under laboratory conditions. Prey/host selections were also tested by offering L. erysimi at various developmental stages to assess the possibility of coexistence between the two species, so the prey preference of H. axyridis when D. rapae parasitize aphids, and the host preference of D. rapae when H. axyridis interfered with the parasitization were detected. We found that H. axyridis could discriminate against mummies rather than non-mummified parasitized aphids. The ladybug showed a significantly positive preference for adult prey when D. rapae turned aphids into mummies, while D. rapae tended to parasitize younger nymphal aphids when H. axyridis was introduced. The present study suggests the prey discrimination against mummies by H. axyridis, and indicates that H. axyridis and D. rapae can avoid resource competition by attacking different and non-overlapping developmental stages of aphid. Thus, H. axyridis and D. rapae can potentially coexist and establish a stable ecosystem in the biological control of L. erysimi.     

The effect of mermithid parasitism on predation of nymphal Baetis bicaudatus (Ephemeroptera) by invertebrates

We investigated how infection by the mermithid nematode Gasteromermis sp. affected predation on its nymphal mayfly host, Baetisbicaudatus, by two invertebrate predators – the stonefly nymphs of Kogotusmodestus and the caddisfly larvae of Rhyacophilahyalinata. Predation trials and behavioral observations were conducted in stream-side, flow-through experimental chambers. When parasitized and unparasitized prey were offered in equal numbers, K. modestus consumed significantly more parasitized than unparasitized nymphs. R. hyalinata consumed equal numbers of both prey types. Behavioral observations of foraging K.␣modestus on parasitized and unparasitized prey suggested that the increased consumption of parasitized nymphs was due to differences in the behavior of infected mayflies in response to the predator. Specifically, parasitized nymphs drifted less often to escape an approaching predator (non-contact encounters) compared to unparasitized nymphs, which increased the number of contact encounters and attacks that occurred between K.␣modestus and parasitized prey. Because all hosts are castrated, these behavioral alterations affect only the fitness of the parasite, which is killed along with its host by invertebrate predation. We present a number of hypotheses to explain why the parasite causes increased predation on its host. These include the large size of the parasite affecting the sensory abilities of the host, the larger energetic costs of escape behavior for parasitized individuals, and natural selection from fish predation against drifting behavior by parasitized individuals. Received: 27 May 1996 / Accepted: 30 September 1996     

Oviposition avoidance of parasitized aphid colonies by the syrphid predator Episyrphus balteatus mediated by different cues

Oviposition decisions made by members of a guild of natural enemies can have evolved to avoid intraguild predation, potentially avoiding the disruption of the extraguild prey control. We have studied the oviposition preference of the aphidophagous predator Episyrphus balteatus De Geer (Diptera: Syrphidae) within colonies of Myzus persicae Sulzer (Hemiptera: Aphididae) in the presence of two developmental stages of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae). Results from a greenhouse choice experiment showed that E. balteatus females lay significantly fewer eggs in colonies with mummified aphids than in unparasitized colonies. Colonies of parasitized, but not yet mummified did not contain significantly fewer eggs than colonies with unparasitized aphids. In three no-choice experiments, we assessed stimuli coming from aphid honeydew, from the aphids themselves and also from extracts of the aphid bodies, and all of these stimuli mediate the discrimination of mummified aphids from healthy aphids. To a lesser extent these stimuli also contribute to the discrimination against aphids that are parasitized but not yet mummified. These results suggest that the effects of these two species could be complementary for the control of M. persicae, since the species that acts as an intraguild predator, E. balteatus, avoids ovipositing on aphid colonies parasitized by the intraguild prey, A. colemani.     

Community structure and stability analysis for intraguild interactions among host, parasitoid, and predator

Intraguild predation (IGP) occurs when one species preys on a competitor species that shares a common resource. Modifying a prey–predator model with prey infection, we propose a model of IG interactions among host, parasitoid, and predator, in which the predator eats parasitized and unparasitized hosts, and the adult parasitoid density is explicitly expressed. Parameter dependences of community structure, including stability of the system, were analytically obtained. Depending on interaction strength (parasitization and predation on unparasitized and parasitized hosts), the model provides six types of community structure: (1) only the host exists, (2) the host and predator coexist stably, (3) the host and parasitoid coexist stably, (4) the host–parasitoid population dynamics are unstable, (5) the three species coexist stably, and (6) the population dynamics of the three species are unstable. In contrast to a traditional prey–predator model with prey infection, which predicts that population dynamics are always locally stable, our model predicts that they are unstable when the parasitization rate is high.     

Inter- and intra-specific host discrimination in gregarious and solitary endoparasitoid wasps

In nature, most species of Lepidoptera are attacked by parasitoids, and some species may be hosts for several parasitoid species. When hosts are parasitized by more than one female of the same species (=superparasitism) or females of different species (=multiparasitism), then intrinsic competition occurs for control of host resources. To reduce competition, some parasitoids are able to recognize the difference between parasitized and unparasitized hosts. Inter- and intra-specific host discrimination were investigated in the two sympatric species, the gregarious Cotesia kariyai (Watanabe) and solitary Meteorus pulchricornis (Wesmael), endoparasitoids of the Oriental armyworm Mythimna separata (Walker). To measure host discrimination, choice experiments were conducted in which females of both species foraged and chose between healthy host larvae and hosts initially parasitized by either C. kariyai or M. pulchricornis. An olfactory test was also performed to examine the discrimination behavior of the two parasitoids. Our results showed that, in oviposition choice tests, both braconid female wasps were able to discriminate between unparasitized hosts and from four to seven day-old hosts previously attacked by conspecific and heterospecific wasps. On the other hand, superparasitism and multiparasitism occurred even in host larvae that were parasitized two days earlier. However, once the immature parasitoids hosts are at larval stage (1st and 2nd instar), super- and multiparasitism were avoided in the two-choice test, but the latter often occurred in the multiple-choice experiment. Host discrimination abilities may have been based on plant volatile signals incurred from damaged plants and internal mechanisms from four to seven post-parasitized hosts.     

Prey Habitat Location by the Cassava Mealybug Predator Exochomus flaviventris: Olfactory Responses to Odor of Plant, Mealybug, Plant–Mealybug Complex, and Plant–Mealybug–Natural Enemy Complex

Exochomus flaviventris Mader is considered to be the most active predator of the cassava mealybug Phenacoccus manihoti Matile–Ferrero in Central Africa. The response of experienced gravid female coccinellids to the odor of cassava plant (var. Zanaga), unparasitized mealybugs, plant–mealybug complex with or without feeding prey (parasitized or not), and plant–mealybug complex with or without conspecific coccinellids was investigated in a Y-tube olfactometer. The odor of uninfested cassava plants was not more attractive than clean air. Dual-choice tests revealed that mealybug-infested plants were preferred to mealybugs alone and mealybug-damaged plants and were the major sources of volatiles that attract females coccinellids to the microhabitat of its prey. The emission of volatile chemicals did not appear to be limited to the infested parts of the plant but did occur systemically throughout the plant. The presence of conspecific coccinellid larvae or adult males did not modify the attractiveness of the mealybug-infested plants. However, when an infested plant with conspecific predator females (alone or with conspecific males) was compared to an infested plant or infested plant with conspecific males, E. flaviventris females showed a preference for the last two sources of odor. The uninfested plant with conspecific males was also preferred to the uninfested plant with conspecific females. In addition, the odor of conspecific males was preferred over that of conspecific females. Female predators preferred the plant infested with unparasitized mealybugs over the plant infested with mealybugs previously parasitized. These results showed that E. flaviventris females use herbivore-induced plant volatiles during foraging and can detect via olfaction the presence of conspecific gravid females and parasitized prey, thus assessing patch suitability from a distance.     

Nymphal performance correlated with adult preference for flowering host plants in a polyphagous mirid bug, Apolygus lucorum (Heteroptera: Miridae)

Apolygus lucorum (Heteroptera: Miridae), a polyphagous mirid bug, often shows a strong preference for flowering host plants. It is hypothesized that host plant selection by phytophagous insects results in a variety of behavioral trade-offs. In this study, the relationship between adult preference and nymphal performance was examined on host plants with their flowers left intact and with flowers removed to investigate potential trade-offs in A. lucorum’s preference for flowering plants. Field trials in 2010 and 2011 showed that adults and nymphs were significantly more abundant on plants with flowers left intact than on those with flowers removed, while oviposition choice trials in field cages revealed that female adults preferred to lay eggs on plants with flowers. Laboratory performance trials demonstrated that adult lifespan and fecundity and nymphal development rate and survival were all significantly higher on plants with flowers compared with plants without flowers. In contrast, sex ratio was not significantly different. Simple linear regression analysis showed positive correlations between (1) adult and nymphal abundances in the field, (2) nymphal development rates and survival with adult fecundity in the laboratory, and (3) adult lifespan with fecundity in the laboratory. Since a positive preference–performance correlation was found for A. lucorum, we conclude that there are no evident behavioral trade-offs for host plant selection by this polyphagous mirid bug.     

Plant response to touch affects the behaviour of aphids and ladybirds

Touching between leaves of the same plant and/or by neighbouring plants is one of the most common mechanical stimuli to which an individual plant has to respond on a daily basis. The possible ecological implications of a plant’s response to touch on plant–insect interactions have not been explicitly investigated. We examined whether plant response to 1 min daily touching over a period of 6 days affects host plant acceptance by the bird cherry-oat aphid Rhopalosiphum padi L. on maize and by the black bean aphid Aphis fabae Scop. on bean, as well as olfactory preference of an aphid predator, seven-spotted ladybird Coccinella septempunctata L. Maize plants responded to touch with significant reduction in plant height, total plant biomass, leaf weight, leaf surface, shoot/root ratio and specific leaf area (SLA), while bean plants responded with reduced stem height and reduced SLA. Both aphid species showed significantly reduced acceptance of touched plants compared with untouched plants. The two aphid species and male and female ladybirds preferred volatiles from untouched plants over those from touched plants. Volatiles in the headspace of touched and untouched plants were collected and identified. Stepwise discriminant analyses identified (E)-nerolidol and (E)-β-caryophyllene in maize and 6-methyl-5-hepten-2-one and an unidentified sesquiterpene in bean as the best discriminating compounds in the volatile profiles of touched plants. Our study suggests that touch-induced changes in plants can potentially affect host plant selection by aphids and habitat searching by ladybirds. Thus, touch-induced changes in plants may have significant effects at higher trophic levels.     

Histopathology of an aphid,Schoutedenia lutea,parasitized by a gall midge,Pseudendaphis sp

Pseudendaphis sp. (Barnes) [Diptera: Cecidomyiidae] is a larval endoparasitoid of the aphidSchoutedenia lutea (van der Goot) [Aphididae: Greenideinae]. A brief investigation of the biology ofPseudendaphis sp. revealed that parasitization by this species occurs only in viviparous instar III to adult life stages of the host aphid. Comparative histology of parasitized, unparasitized and starved aphids was used to evaluate proposed mechanisms of pathogenesis. Parasitization byPseudendaphis sp. was found to cause the destruction of host embryos and pathological changes in the host fat body, yet resulted in an increase in the number of host mycetocytes. There was no evidence of injury to host tissues through direct physical attack, a cytolytic enzyme or starvation-like factors. Remaining hypotheses for altered host histologies in parasitized aphids are selective nutrient depletion and production of a non-cytolytic bioactive substance by thePseudendaphis larvae.      

Interaction of a host plant and its holoparasite: effects of previous selection by the parasite

If parasites decrease the fitness of their hosts one could expect selection for host traits (e.g. resistance and tolerance) that decrease the negative effects of parasitic infection. To study selection caused by parasitism, we used a novel study system: we grew host plants (Urtica dioica) that originated from previously parasitized and unparasitized natural populations (four of each) with or without a holoparasitic plant (Cuscuta europaea). Infectivity of the parasite (i.e. qualitative resistance of the host) did not differ between the two host types. Parasites grown with hosts from parasitized populations had lower performance than parasites grown with hosts from unparasitized populations, indicating host resistance in terms of parasite’s performance (i.e. quantitative resistance). However, our results suggest that the tolerance of parasitic infection was lower in hosts from parasitized populations compared with hosts from unparasitized populations as indicated by the lower above‐ground vegetative biomass of the infected host plants from previously parasitized populations.     

Natural enemy composition rather than richness determines pest suppression

Natural enemy (NE) biodiversity is thought to play an important role in agricultural pest suppression. However, the relative importance of the number of NE species (species richness), versus the particular combinations of species (species composition), in determining aphid suppression and ultimately crop yields, remains poorly understood. We tested the effects of NE richness and composition on pea aphids Acyrthosiphon pisum (Harris) and broad bean plants Vicia faba (Linn.). We used the larvae of two predator species, the ladybird Adalia bipunctata (Linn.) and the green lacewing Chrysopa carnea (Stephens), and the parasitic wasp Aphidius ervi (Haliday) as enemies. NEs generally reduced aphid density but did not increase final plant biomass, despite a significant negative correlation between aphid density and plant biomass. Among NE treatments, species richness had an inconsistent effect on aphid density. The composition of NEs within richness levels also affected final aphid density: the ladybird was a key species among the treatments in controlling aphid density and was especially effective in combination with the parasitoid. This ladybird/parasitoid combination also appeared to drive the higher level of suppression observed at the two, relative to three, species richness levels. Although these three species of aphid NEs are commonly used in aphid control, this is the first study, to our knowledge, that simultaneously examined these three species and highlighted the composition effect between the A. bipunctata and A. ervi. In conclusion, increasing NE species richness had an inconsistent effect on aphid density. Meanwhile, the presence of a key species (the ladybird) and its combination with a parasitoid was an important determinant of aphid biological control.     

Intraguild predation and interference by the mealybug predator Cryptolaemus montrouzieri on the parasitoid Leptomastix dactylopii

The compatibility of the encyrtid parasitoid Leptomastix dactylopii with the coccinellid beetle Cryptolaemus montrouzieri against the citrus mealybug, Planococcus citri, is determined by the extent of intraguild predation and interference by the predator. We tested the preference of the adults and fourth-instar larvae of C. montrouzieri for healthy mealybugs and parasitized mealybugs harboring 1-, 4-, 7- and 14-day-old parasitoid larvae. The experiments were conducted in no-choice (only unparasitized mealybugs or parasitized mealybugs of one parasitoid age were offered at one time) and choice (unparasitized and parasitized mealybugs of a specific age were offered simultaneously) tests. Both the adults and larvae of C. montrouzieri fed on unparasitized and parasitized mealybugs but strongly discriminated against the hardened mummies (14 days old). We also investigated the influence of the presence of C. montrouzieri to the foraging effectiveness of L. dactylopii. The level of parasitism by L. dactylopii was reduced from about 13 to 6% when the number of the C. montrouzieri was increased from zero to four. We recommended that the releases of C. montrouzieri should be conducted 14 days after the releases of L. dactylopii to reduce intraguild predation on the parasitized mealybugs and to avoid interference with the foraging parasitoids.     

Could hosts considered as low quality for egg-laying be considered as high quality for host-feeding?

When parasitoid females encounter a host, they can either lay an egg and thus invest in current reproduction or feed on the host and thus invest in future reproduction. However, hosts could have different values according to their parasitized status. Whereas already parasitized hosts represent poor quality for egg-laying, they could have a high nutritive value for feeding. Moreover, the optimal strategy adopted generally depends on the females’ physiological state. In this study, the impact of the females’ physiological state on their reproductive strategies was investigated in the solitary parasitoid Anisopteromalus calandrae. We analysed how their age and diet influenced (i) the use of hosts (feeding vs. oviposition) and (ii) host selection (previously parasitized vs. unparasitized). Our results show that both age and diet influence the reproductive strategy of A. calandrae females: old females fed with the poorer diet laid fewer eggs and made more host-feeding than others. Females also showed a preference for already parasitized hosts for feeding. This strategy cannot be explained by the nutritive value of haemolymph, as parasitized hosts carry fewer lipids. However, as parasitized hosts are also paralyzed, it could be less costly to feed on them than on unparasitized hosts.     

A parasite's modification of host behavior reduces predation on its host

Parasite modification of host behavior is common, and the literature is dominated by demonstrations of enhanced predation on parasitized prey resulting in transmission of parasites to their next host. We present a case in which predation on parasitized prey is reduced. Despite theoretical modeling suggesting that this phenomenon should be common, it has been reported in only a few host–parasite–predator systems. Using a system of gregarine endosymbionts in host mosquitoes, we designed experiments to compare the vulnerability of parasitized and unparasitized mosquito larvae to predation by obligate predatory mosquito larvae and then compared behavioral features known to change in the presence of predatory cues. We exposed Aedes triseriatus larvae to the parasite Ascogregarina barretti and the predator Toxohrynchites rutilus and assessed larval mortality rate under each treatment condition. Further, we assessed behavioral differences in larvae due to infection and predation stimuli by recording larvae and scoring behaviors and positions within microcosms. Infection with gregarines reduced cohort mortality in the presence of the predator, but the parasite did not affect mortality alone. Further, infection by parasites altered behavior such that infected hosts thrashed less frequently than uninfected hosts and were found more frequently on or in a refuge within the microcosm. By reducing predation on their host, gregarines may be acting as mutualists in the presence of predation on their hosts. These results illustrate a higher‐order interaction, in which a relationship between a species pair (host–endosymbiont or predator–prey) is altered by the presence of a third species.     

Superparasitism and host discrimination byEphedrus cerasicola [Hym.: Aphidiidae], an aphidiid parasitoid ofMyzus persicae [Hom.: Aphididae]

Myzus persicae (Sulzer) at different densities (1 to 120 aphids) on a paprika plant in a 1.8 dm³ cage were exposed at 21°C to single females of the parasitoidEphedrus cerasicola Stary. Three different exposure periods were used: 1 hr, 6 hrs, 24 hrs. The aphids were dissected 6 days after parasitization. Superparasitism was measured as number of hosts superparasitized and number of parasitoid larvae per aphid. It attained a maximum around host density=5 and decreased with increasing host density and decreasing exposure time. Almost no superparasitism occurred during the 1st hour. A non-random larval distribution indicated thatE. cerasicola discriminates between unparasitized and parasitized aphids, but probably not between aphids with different numbers of parasitoid eggs. Larvae in superparasitized aphids developed slower than single larvae. The supernumerary larvae died during the 1st instar, probably killed by chemical means since no physical attacks between larvae have been observed.     

Larvicidal activity of lectins onLucilia cuprina: mechanism of action

Foraging behaviour and host-instar preference of young and old females of the solitary aphid parasitoid,Lysiphlebus cardui Marshall (Hymenoptera: Aphidiidae), were studied in the laboratory. The analysis of interactions between parasitoids and different stages ofAphis fabae cirsiiacanthoidis Scop. (Homoptera: Aphididae) revealed that encounter rates between aphids and parasitoid females and defence reactions of the aphids influenced the degree to which a particular aphid age class is parasitized. Encounter rates between hosts and parasitoid females depended on the foraging pattern of the parasitoid, which varied with age. In mixed aphid colonies patch residence time increased with parasitoid age. Furthermore, younger parasitoids (≦1 day old) laid more eggs into second and third instars, while older parasitoids (≧4 days old) did not show distinct host instar preferences. It is suggested that the oviposition behaviour ofL. cardui is influenced by the physiological state, i.e. the age of the wasp.     

Role of terpenes from aphid-infested potato on searching and oviposition behavior of Episyrphus balteatus

To cope with pathogen and insect attacks, plants develop different mechanisms of defence, in both direct （physical and chemical） and indirect ways （attractive volatiles to entomophagous beneficials）. Plants are then able to express traits that facilitate ＂top-down＂ control of pests by attracting herbivore predators. Here we investigate the indirect defence mechanism of potato plants by analyzing the volatile patterns of both healthy and aphid- infested plants. Important changes in the emitted terpene pattern by the Myzus persicae infested host plant were observed. Using Solid Phase MicroExtraction （SPME） and GC-MS, the （E）-fl-farnesene （EBF） appeared to be emitted by aphid-infested potato and not by healthy plants. To assess the infochemical role of these volatile releases after aphid damage on the aphidophagous predators Episyrphus balteams, the hoverfly foraging behavior was assessed using the Observer 5.0 software （Noldus, Wageningen, The Netherlands）. Aphidfree potato plants were also used as a control volatile source in the predator behavioral study. While aphid-infested plants induced efficient searching and acceptation behaviors leading to egg-laying, no kairomonal effect of healthy potato plants was observed, leading to longer immobility durations and shorter searching periods in the net cage. High oviposition rate of E. balteatus was observed when aphid-infested potato was used （mean of 48.9 eggs per laying and per female）. On the other hand, no egg was produced by the hoverfly on healthy aphid-free plants. The E. balteatus foraging and reproductive behaviors according to the volatile emission from aphid-infested plants are discussed in relation to the potential use of active infochemical molecules in integrated aphid pest management.     

中红侧沟茧蜂寄生对寄主粘虫血淋巴糖类、脂类和蛋白质含量的影响

为揭示寄生蜂寄生对其寄主的生理调控机制, 室内对中红侧沟茧蜂Microplitis mediator寄生与未被寄生寄主粘虫Mythimna separata幼虫血淋巴中糖类、脂类和蛋白含量变化进行了测定。结果显示: 在滞育与非滞育条件下, 被寄生的粘虫血淋巴中糖原浓度均比未被寄生的粘虫高。滞育条件下寄生后12 d差异显著（P<0.05）, 被寄生粘虫糖原含量为7.93 μg/mL, 未被寄生粘虫糖原含量为4.70 μg/mL; 非滞育条件下寄生后6 d差异显著（P<0.05）, 被寄生粘虫糖原含量为14.35 μg/mL, 未被寄生粘虫糖原含量为5.47 μg/mL。海藻糖含量测定结果显示, 在滞育条件下寄生蜂对被寄生粘虫无明显影响, 而非滞育条件下影响效果差异显著（P<0.05）, 寄生后4 d被寄生粘虫海藻糖含量为46.82 μg/mL, 未被寄生粘虫含量为26.72 μg/mL。在滞育与非滞育两种条件下, 寄生与未被寄生寄主脂类和蛋白含量没有显著性差异。结果说明: 寄生蜂的存在使寄主血淋巴中的糖原含量增高; 非滞育条件是影响被寄生粘虫海藻糖含量变化主要因素; 粘虫对中红侧沟茧蜂的寄生表现相当强的适应性和忍受力。     

Parasitism by Cuscuta pentagona attenuates host plant defenses against insect herbivores

Considerable research has examined plant responses to concurrent attack by herbivores and pathogens, but the effects of attack by parasitic plants, another important class of plant-feeding organisms, on plant defenses against other enemies has not been explored. We investigated how attack by the parasitic plant Cuscuta pentagona impacted tomato (Solanum lycopersicum) defenses against the chewing insect beet armyworm (Spodoptera exigua; BAW). In response to insect feeding, C. pentagona-infested (parasitized) tomato plants produced only one-third of the antiherbivore phytohormone jasmonic acid (JA) produced by unparasitized plants. Similarly, parasitized tomato, in contrast to unparasitized plants, failed to emit herbivore-induced volatiles after 3 d of BAW feeding. Although parasitism impaired antiherbivore defenses, BAW growth was slower on parasitized tomato leaves. Vines of C. pentagona did not translocate JA from BAW-infested plants: amounts of JA in parasite vines grown on caterpillar-fed and control plants were similar. Parasitized plants generally contained more salicylic acid (SA), which can inhibit JA in some systems. Parasitized mutant (NahG) tomato plants deficient in SA produced more JA in response to insect feeding than parasitized wild-type plants, further suggesting cross talk between the SA and JA defense signaling pathways. However, JA induction by BAW was still reduced in parasitized compared to unparasitized NahG, implying that other factors must be involved. We found that parasitized plants were capable of producing induced volatiles when experimentally treated with JA, indicating that resource depletion by the parasite does not fully explain the observed attenuation of volatile response to herbivore feeding. Collectively, these findings show that parasitic plants can have important consequences for host plant defense against herbivores.     

Advanced phenology of intraguild predators shifts herbivore host plant preference and performance

1. The abundance of insect herbivores is mediated by interactions with higher and lower trophic levels. This research asks (i) how phenological change across trophic levels affects host plant quality and selection for aphids, and (ii) what higher trophic level mechanisms drive aphid abundance. 2. Ligusticum porteri is a perennial host for the sap-feeding aphid Aphis asclepiadis and intraguild mirid predators (chiefly Lygus hesperus) in Colorado. We used long-term observational data to discover that aphids and mirids respond differently to phenological cues. These unique responses can impact aphid abundance through changes to host plant selection and quality. 3. We used behavioural choice assays to assess how advanced mirid phenology influences aphid host plant selection. More alates landed and reproduced on mirid-free control plants relative to host plants with prior mirid feeding. However, this preference did not correlate with aphid performance when we compared aphid relative growth rates between treatments. This suggests that advanced mirid phenology would impact aphid populations more through host plant choice, rather than reductions in host quality. The addition of mirids to experimental aphid colonies also demonstrated reduced aphid colony growth via predation. 4. We measured plant cues involved in host selection and found differences in volatile composition between plants with prior mirid feeding compared to control plants, providing the potential for aphids to detect enemy-free space using volatile cues.