How oilseed rape (Brassica napus) genotype influences pollen beetle (Meligethes aeneus) oviposition

Oviposition of phytophagous insects is determined either by adaptive behaviours allowing evaluation and response to host plant quality and/or by nutritional constraints occurring during oogenesis. Besides differences found among host plant species, plant intraspecific diversity can also affect insect oviposition. However, to date few studies have extensively investigated the factors accounting for the effect of this intraspecific variation. We addressed this question using oilseed rape (Brassica napus) and the pollen beetle (Meligethes aeneus), a phytophagous insect that uses the same plants and plant organs both for feeding and laying eggs. Our objectives were to test for a genotypic effect of oilseed rape on pollen beetle oviposition and identify the origin of the possible intergenotypic differences. We tested three hypotheses: oviposition is directly linked to (1) the amount of food eaten; (2) the nutritional quality of the food eaten; (3) a preference of females for certain plant genotypes. Results showed intergenotypic differences in both the number and the size of eggs laid. The factor that best accounted for most of these differences was the amount of food eaten. Nutritional quality of the pollen was of minor importance and females exhibited no preference among genotypes. These results reveal the importance of adult feeding on subsequent oviposition in phytophagous insects, an often neglected factor which partly determines the amount of energy available for oogenesis. Taking into account this factor may be of crucial importance in studies conducted on synovogenic insect species feeding on the same plant on which they lay eggs.     

The structure of feeding behavior in a phytophagous insect (Hylobius abietis)

Analysis of the feeding behavior of animals using such a high temporal resolution that meals can be defined may improve our understanding of the mechanisms regulating feeding. Meals can be distinguished in an ethologically meaningful manner by using the ‘meal criterion’, the shortest non‐feeding interval between feeding bouts recognized as meals. However, such a criterion has only been determined for a few insect species. Applying a recent method developed for assessing meal criteria for vertebrates, we determined the meal criterion for Hylobius abietis (L.) (Coleoptera: Curculionidae) based on data from video recordings of single individuals feeding on seedlings of Norway spruce, Picea abies (L.) Karst. (Pinaceae). The pine weevil is an economically important pest insect, because it feeds on the stem bark of planted conifer seedlings. Weevils had 4–5 meals per day. Each meal lasted about 24 min during which about 13 mm² of bark per meal were removed. Females had longer total meal durations and longer non‐feeding intervals within meals than males. Girdling seedlings did not affect the weevils' feeding properties. The size of meals was significantly correlated with the duration of non‐feeding intervals before and after them. This study is one of few describing the feeding behavior of an insect at a temporal resolution that allows individual meals to be distinguished. With more meal‐related data from insects available, differences in meal properties may be interpreted based on phylogeny, ecology, and physiology. Our results may also assist in the setup and interpretation of studies of plant‐insect interactions, and facilitate the evaluation and development of methods to protect plants against herbivores.     

Perception of insect feeding by plants

The recognition of phytophagous insects by plants induces a set of very specific responses aimed at deterring tissue consumption and reprogramming metabolism and development of the plant to tolerate the herbivore. The recognition of insects by plants requires the plant’s ability to perceive chemical cues generated by the insects and to distinguish a particular pattern of tissue disruption. Relatively little is known about the molecular basis of insect perception by plants and the signalling mechanisms directly associated with this perception. Importantly, the insect feeding behaviour (piercing‐sucking versus chewing) is a decisive determinant of the plant’s defence response, and the mechanisms used to perceive insects from different feeding guilds may be distinct. During insect feeding, components of the saliva of chewing or piercing‐sucking insects come into contact with plant cells, and elicitors or effectors present in this insect‐derived fluid are perceived by plant cells to initiate the activation of specific signalling cascades. Although receptor–ligand interactions controlling insect perception have yet not been molecularly described, a significant number of regulatory components acting downstream of receptors and involved in the activation of defence responses against insects has been reported. Some of these regulators mediate changes in the phytohormone network, while others directly control gene expression or the redox state of the cell. These processes are central in the orchestration of plant defence responses against insects.     

Plant genotype affects the quality of oilseed rape (Brassica napus) for adults and larvae of the pollen beetle (Meligethes aeneus)

Plant quality is one of the main factors influencing the fitness of phytophagous insects. Plant quality can vary not only among genotypes of the same host plant species, but also relative to the insect sex or its life stage. In the present study, the performance of larvae and adults of the pollen beetle (Meligethes aeneus F., Coleoptera: Nitidulidae), a major insect pest of oilseed rape crops, is compared on six genotypes of oilseed rape (Brassica napus). All of the traits that are measured vary among genotypes, and comprise larval developmental duration, life span of unfed emerging adults and survival time of field‐sampled adults fed with pollen from the different genotypes. No correlation is found between insect performance and quantity of food available, showing that the quality of the food (i.e. pollen) is the fitness determinant for this insect species. Additionally, the performance of larvae and adults is also not correlated despite use of the same plant genotypes, suggesting that the determinants of pollen quality differ at least partially between both life stages. It is hypothesized that this may be a result of extensive differences in diet breadth between the life stages: larvae are specialists of brassicaceous plants, whereas adults are generalists. Finally, it is suggested that the manipulation of plant quality to increase pollen beetle development time may comprise a valuable strategy for favouring biological control by natural enemies of this pest; for example, as a result of extending the vulnerability window of larvae to attack by parasitoids.     

Solar ultraviolet-B radiation alters the attractiveness of Arabidopsis plants to diamondback moths (Plutella xylostella L.): impacts on oviposition and involvement of the jasmonic acid pathway

Solar ultraviolet-B radiation (UV-B) can have large impacts on the interactions between plants and herbivorous insects. Several studies have documented effects of UV-B-induced changes in plant tissue quality on the feeding performance of insect larvae. In contrast, the effects of UV-B-induced plant responses on the behavior of adult insects have received little attention. We carried out a series of field and glasshouse experiments using the model plant Arabidopsis thaliana L. and the crucifer-specialist insect Plutella xylostella L. (diamondback moth) to investigate the effects of UV-B on natural herbivory and plant–insect interactions. Natural herbivory under field conditions was less severe on plants exposed to ambient UV-B than on plants grown under filters that attenuated the UV-B component of solar radiation. This reduced herbivory could not be accounted for by effects of UV-B on larval feeding preference and performance, as P. xylostella caterpillars did not respond to changes in plant quality induced by UV-B. In contrast, at the adult stage, the insects presented clear behavioral responses: P. xylostella moths deposited significantly more eggs on plants grown under attenuated UV-B levels than on plants exposed to ambient UV-B. The deterring effect of UV-B exposure on insect oviposition was absent in jar1-1, a mutant with impaired jasmonic acid (JA) sensitivity, but it was conserved in mutants with altered ethylene signaling. The jar1-1 mutant also presented reduced levels of UV-absorbing phenolic compounds than the other genotypes that we tested. Our results suggest that variations in UV-B exposure under natural conditions can have significant effects on insect herbivory by altering plant traits that female adults use as sources of information during the process of host selection for oviposition. These effects of natural UV-B on plant quality appear to be mediated by activation of signaling circuits in which the defense-related hormone JA plays a functional role.     

Ecological and Evolutionary Interactions between Wild Crucifers and Their Herbivorous Insects

Abstract Insects feeding on ten species of wild crucifer were investigated. Differences in host plant range and insect community structure were examined with regard to anti-herbivore defense mechanisms. Most of the crucifer species deterred insect herbivory by disappearing in the summer or by lowering their intrinsic quality as food for insects. Species with these defense mechanisms were exploited by only a few specialized herbivorous insects that seemed to have counter defenses. The plants without these defense mechanisms were used by many herbivorous insect species. Rorippa indica lacked direct defenses, but supported a low total density of herbivore individuals. This crucifer has an indirect defense mechanism: ants attracted to floral nectar defended the plant from deleterious herbivores. Crucifers that disappeared seasonally lacked other anti-herbivore defense mechanisms. This suggests that the phonological response is an alternative other responses to herbivore attack.     

Leaf shape variation and herbivore consumption and performance: a case study with Ipomoea hederacea and three generalists

The effect of leaf shape variation on plant-herbivore interactions has primarily been studied from the perspective of host seeking behavior. Yet for leaf shape to affect plant-herbivore coevolution, there must be reciprocal effects of leaf shape variation on herbivore consumption and performance. We investigated whether alternative leaf morphs affected the performance of three generalist insect herbivores by taking advantage of a genetic polymorphism and developmental plasticity in leaf shape in the Ivyleaf morning glory, Ipomoea hederacea. Across four experiments, we found variable support for an effect of leaf shape genotype on insects. For cabbage loopers (Trichoplusia ni) and corn earworms (Helicoverpa zea) we found opposing, non-significant trends: T. ni gained more biomass on lobed genotypes, while H. zea gained more biomass on heart-shaped genotypes. For army beetworms (Spodoptera exigua), the effects of leaf shape genotype differed depending on the age of the plants and photoperiod of growing conditions. Caterpillars feeding on tissue from older plants (95 days) grown under long day photoperiods had significantly greater consumption, dry biomass, and digestive efficiency on lobed genotypes. In contrast, there were no significant differences between heart-shaped and lobed genotypes for caterpillars feeding on tissue from younger plants (50 days) grown under short day photoperiods. For plants grown under short days, we found that S. exigua consumed significantly less leaf area when feeding on mature leaves than juvenile leaves, regardless of leaf shape genotype. Taken together, our results suggest that the effects of leaf shape variation on insect performance are likely to vary between insect species, growth conditions of the plant, and the developmental stage and age of leaves sampled. Handling editor: May Berenbaum.     

Genotypic variation in growth and resistance to insect herbivory in silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis>) seedlings

If herbivory is unevenly distributed among different types of plants, or if individual plants differ in their response to herbivory, herbivores may affect seedling growth and survival, and consequently plant population structure. In this study we examined variation in resistance to insect herbivory and in growth responses to feeding among 20 silver birch (Betula pendula Roth) genotypes representing variation within a natural population. Birch seedlings were grown in dense stands in random arrangement so that seedlings of different genotypes competed with each other. On insect exposure plots natural colonization of insects was allowed, and insect removal plots were sprayed with insecticide. Resistance to insect herbivory was measured as the inverse of leaf damage, and growth responses of seedlings to feeding were determined as the change in seedling height relative to the amount of damage. Resistance varied significantly among genotypes, but growth responses to feeding did not. In fertilized seedlings, resistance correlated negatively with height, indicating a trade-off between resistance and growth. The absence of such a correlation in non-fertilized seedlings is a sign of environmental effects on the cost of resistance. Growth responses to feeding did not correlate with either resistance or growth. Nevertheless, different effects of the actual damage on height increase changed the positions of the genotypes in the size hierarchy of the experimental populations. Thus, even moderate levels of insect herbivory can change the outcome of competitive interactions between birch genotypes.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Effects of Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) growing conditions and nutrient content on the performance of a leaf-mining fly,Hydrellia purcelli Deeming (Diptera: Ephydridae)

Host plant quality for insects used in weed biological control influences their performance and hence their ability to suppress target host populations. Determining the specific response of these insects to the quality of their host is important because phytophagous insects have variable tolerances of the different constituents of host plant quality, most notably dietary nitrogen (N), but also other physical and chemical components. The invasive aquatic weed Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) was cultivated under varying nutrient conditions to determine the influence of plant quality on immature survival, development, larval mining, reproductive output and adult longevity of a leaf-mining fly Hydrellia purcelli Deeming (Diptera: Ephydridae). Additionally, field-collected H. verticillata was included in the investigations to assess the potential performance of H. purcelli in the field. Variation in plant tissue N and phosphorus (P) concentrations had no effects on larval survival, female fecundity, or adult longevity, but high levels of N and P were associated with reduced immature development times and higher body mass of females. Overall, plant quality factors not measured in this study appeared to have a greater impact on the performance of the fly, rather than dietary N and P. The results provided insights into optimal mass-rearing conditions for H. purcelli and the potential performance of the fly in the field in South Africa. Furthermore, the results demonstrate the importance of considering other aspects of plant quality for insect agents, in addition to dietary N and P, when developing mass-rearing protocols or predicting their potential impact in the field.     

How do herbivorous insects respond to drought stress in trees?

Increased frequency and severity of drought, as a result of climate change, is expected to drive critical changes in plant–insect interactions that may elevate rates of tree mortality. The mechanisms that link water stress in plants to insect performance are not well understood. Here, we build on previous reviews and develop a framework that incorporates the severity and longevity of drought and captures the plant physiological adjustments that follow moderate and severe drought. Using this framework, we investigate in greater depth how insect performance responds to increasing drought severity for: (i) different feeding guilds; (ii) flush feeders and senescence feeders; (iii) specialist and generalist insect herbivores; and (iv) temperate versus tropical forest communities. We outline how intermittent and moderate drought can result in increases of carbon‐based and nitrogen‐based chemical defences, whereas long and severe drought events can result in decreases in plant secondary defence compounds. We predict that different herbivore feeding guilds will show different but predictable responses to drought events, with most feeding guilds being negatively affected by water stress, with the exception of wood borers and bark beetles during severe drought and sap‐sucking insects and leaf miners during moderate and intermittent drought. Time of feeding and host specificity are important considerations. Some insects, regardless of feeding guild, prefer to feed on younger tissues from leaf flush, whereas others are adapted to feed on senescing tissues of severely stressed trees. We argue that moderate water stress could benefit specialist insect herbivores, while generalists might prefer severe drought conditions. Current evidence suggests that insect outbreaks are shorter and more spatially restricted in tropical than in temperate forests. We suggest that future research on the impact of drought on insect communities should include (i) assessing how drought‐induced changes in various plant traits, such as secondary compound concentrations and leaf water potential, affect herbivores; (ii) food web implications for other insects and those that feed on them; and (iii) interactions between the effects on insects of increasing drought and other forms of environmental change including rising temperatures and CO₂ levels. There is a need for larger, temperate and tropical forest‐scale drought experiments to look at herbivorous insect responses and their role in tree death.     

Aphid and host‐plant genotype × genotype interactions under elevated CO2

1. Elevated CO₂ can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO₂ and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype‐specific responses to elevated CO₂. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype‐specific effects and possible host plant‐by‐insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO₂ (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO₂ concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO₂ on aphid density was dependent on host plant genotype; the density of aphids in high CO₂ decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO₂ was found, nor did we find significant genotype‐by‐genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO₂ for some plant genotypes. The likely impact of genotype‐specific responses on future changes in the genetic structure of plant and insect populations is discussed.     

General esterases of Bemisia tabaci (Hemiptera: Aleyrodidae) change in response to feed on cotton varieties

The esterase enzymes are a major component of insect detoxification systems and play a crucial role in hydrolyzing lots of xenobiotic compounds. Among insect, generalist herbivores can exhibit developed biochemical defences as a result of exposing to a wide range of plant chemical compounds. To overcome this ability, host plants may affect the level of hydrolases in herbivore insects feeding on. To examine this hypothesis, in the present study total esterase activity was investigated in a highly polyphagous whitefly, Bemisia tabaci, reared on six different varieties of cotton, Gossypium hirsutum. Results showed significant differences in esterase activity of B. tabaci feeding on the host plant varieties. The highest esterase activities were detected in whiteflies feeding on Sk-Tb and Siokra varieties, whereas those whiteflies that feed on Hopicala variety exhibited the least esterase activities. Our findings highlight the important role of host plants in detoxification ability of herbivore insects. The importance of these findings in biology of insect pests and their applications in integrated pest management programmes of B. tabaci have been discussed in detail.     

Jasmonic Acid-Mediated-Induced Resistance in Groundnut (Arachis hypogaea L.) Against Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

Jasmonic acid (JA) acts as a signal molecule to induce resistance in plants against herbivores and its levels are elevated in plants after wounding or insect damage. Groundnut is an important crop in many tropical and subtropical regions worldwide, but there is surprisingly little knowledge on its induced defenses against herbivores. The effect of JA as a spray on induced resistance in three groundnut genotypes, namely, ICGV 86699 (resistant), NCAc 343 (resistant), and TMV 2 (susceptible), against Helicoverpa armigera was studied. The activity of oxidative enzymes [peroxidase (POD) and polyphenol oxidase (PPO)] and the amounts of other host plant defense components [total phenols, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and protein content] were recorded at 24, 48, 72, and 96 h after pretreatment (1 day) with JA followed by infestation with H. armigera (PJA + HIN) and H. armigera infestation with simultaneous JA application (HIN + JA) to understand the consequences of induced resistance in groundnut. The plant damage, larval survival, and larval weights were also recorded. There was a significant increase in POD and PPO activities and in the amounts of total phenols, H₂O₂, MDA, and proteins in PJA + HIN- and JA + HIN-treated plants as compared to the plants treated with JA and infested with H. armigera individually and to untreated control plants. Among all the genotypes, the strongest induction of defense was observed in the ICGV 86699 genotype. It is concluded that pretreatment with JA and its application during low levels of insect infestation can increase the levels of host plant resistance against herbivorous insects and reduce the pest-associated losses in groundnut.     

Plant‐mediated interactions between two herbivores differentially affect a subsequently arriving third herbivore in populations of wild cabbage

• Plants are part of biodiverse communities and frequently suffer from attack by multiple herbivorous insects. Plant responses to these herbivores are specific for insect feeding guilds: aphids and caterpillars induce different plant phenotypes. Moreover, plants respond differentially to single or dual herbivory, which may cascade into a chain of interactions in terms of resistance to other community members. Whether differential responses to single or dual herbivory have consequences for plant resistance to yet a third herbivore is unknown.
• We assessed the effects of single or dual herbivory by Brevicoryne brassicae aphids and/or Plutella xylostella caterpillars on resistance of plants from three natural populations of wild cabbage to feeding by caterpillars of Mamestra brassicae. We measured plant gene expression and phytohormone concentrations to illustrate mechanisms involved in induced responses.
• Performance of both B. brassicae and P. xylostella was reduced when feeding simultaneously with the other herbivore, compared to feeding alone. Gene expression and phytohormone concentrations in plants exposed to dual herbivory were different from those found in plants exposed to herbivory by either insect alone. Plants previously induced by both P. xylostella and B. brassicae negatively affected growth of the subsequently arriving M. brassicae. Furthermore, induced responses varied between wild cabbage populations.
• Feeding by multiple herbivores differentially activates plant defences, which has plant‐mediated negative consequences for a subsequently arriving herbivore. Plant population‐specific responses suggest that plant populations adapt to the specific communities of insect herbivores. Our study contributes to the understanding of plant defence plasticity in response to multiple insect attacks.

     

Kairomonal Responses of Natural Enemies and Associates of the Southern Ips (Coleoptera: Curculionidae: Scolytinae) to Ipsdienol, Ipsenol and Cis-Verbenol

Bark beetle infested pines are an ephemeral habitat utilized by a diverse assemblage of insects. Although many bark beetle insect associates have little or no measurable impact on bark beetle brood production, some reduce brood production by either competing with brood for the limited phloem tissue or by feeding on brood. Several studies have observed synchrony between the colonization of hosts by bark beetles and the arrival of insect associates. Some insect associates mediate synchrony with bark beetle mass attacks with kairomonal responses to bark beetle aggregation pheromones. The objectives of this study were to document the community of Coleoptera associated with the southern Ips (Ips avulsus, Ips calligraphus and Ips grandicollis) and to test the hypothesis that synchrony of insect associates with the southern Ips is mediated by kairomonal responses to aggregation pheromones. A large community of Coleoptera (109 species) was recorded from traps baited with southern Ips pheromones. A significant treatment effect was observed for the guilds of meristem feeders, natural enemies and woodborers. The southern Ips pheromone ipsenol was broadly attractive to meristem feeders, natural enemies and woodborers and in general blends were more attractive than individual compounds. These results demonstrate that a diverse community of Coleoptera is associated with the southern Ips and that several members of this community facilitate synchrony with kairomonal responses to southern Ips aggregation pheromones.     

Host‐associated genetic differentiation in a seed parasitic weevil Rhinusa antirrhini (Coleptera: Curculionidae) revealed by mitochondrial and nuclear sequence data

Plant feeding insects and the plants they feed upon represent an ecological association that is thought to be a key factor for the diversification of many plant feeding insects, through differential adaptation to different plant selective pressures. While a number of studies have investigated diversification of plant feeding insects above the species level, relatively less attention has been given to patterns of diversification within species, particularly those that also require plants for oviposition and subsequent larval development. In the case of plant feeding insects that also require plant tissues for the completion of their reproductive cycle through larval development, the divergent selective pressure not only acts on adults, but on the full life history of the insect. Here we focus attention on Rhinusa antirrhini (Curculionidae), a species of weevil broadly distributed across Europe that both feeds on, and oviposits and develops within, species of the plant genus Linaria (Plantaginaceae). Using a combination of mtDNA (COII) and nuclear DNA (EF1‐α) sequencing and copulation experiments we assess evidence for host associated genetic differentiation within R. antirrhini. We find substantial genetic variation within this species that is best explained by ecological specialisation on different host plant taxa. This genetic differentiation is most pronounced in the mtDNA marker, with patterns of genetic variation at the nuclear marker suggesting incomplete lineage sorting and/or gene flow between different host plant forms of R. antirrhini, whose origin is estimated to date to the mid‐Pliocene (3.77 Mya; 2.91–4.80 Mya).     

Resistance to 16 diverse species of herbivorous insects within a population of goldenrod,Solidago altissima: genetic variation and heritability

Summary Genetic variation in resistance to 16 species of herbivorous insects was studied in 18 clones of Solidago altissima growing in an old field near Ithaca, New York, USA. Resistance to each insect, defined as the abundance of a species attacking a particular host genotype relative to other genotypes, was measured in both the natural stand and in two experimental gardens. The heritability of resistance was estimated by parent-offspring regression and sibcorrelation. The primary result was that clones differed in resistance to 15 of 16 insect species. The resistance of genotypes to these insect species remained relatively constant over the four years of the study. However, for only 10 of these resistances were the heritability estimates significantly different from zero. Thus the common assumption of plant-insect studies — that phenotypic variation in insect abundance is closely correlated with underlying genetic variation — is only conditionally true. There is heritable variation in resistance to many insects, but not all. The insects for which we observed heritable variation in plant resistance represent five different orders and several functional groups, including leaf chewers, phloem and xylem feeders, and gall formers. There was no apparent pattern between the degree of heritability of plant resistance and the destructiveness, feeding method, breadth of host range, or taxonomic group of the insects. The lack of marked heritable variation in resistance to some insects may be the result of (a) reduced variation caused by strong selection during prolonged or repeated insect outbreaks, and (b) genotype-environment interactions that obscure differences among genotypes.     

Influence of presence and spatial arrangement of belowground insects on host‐plant selection of aboveground insects: a field study

Abstract 1. Several studies have shown that above‐ and belowground insects can interact by influencing each others growth, development, and survival when they feed on the same host‐plant. In natural systems, however, insects can make choices on which plants to oviposit and feed. A field experiment was carried out to determine if root‐feeding insects can influence feeding and oviposition preferences and decisions of naturally colonising foliar‐feeding insects. 2. Using the wild cruciferous plant Brassica nigra and larvae of the cabbage root fly Delia radicum as the belowground root‐feeding insect, naturally colonising populations of foliar‐feeding insects were monitored over the course of a summer season. 3. Groups of root‐infested and root‐uninfested B. nigra plants were placed in a meadow during June, July, and August of 2006 for periods of 3 days. The root‐infested and the root‐uninfested plants were either dispersed evenly or placed in clusters. Once daily, all leaves of each plant were carefully inspected and insects were removed and collected for identification. 4. The flea beetles Phyllotreta spp. and the aphid Brevicoryne brassicae were significantly more abundant on root‐uninfested (control) than on root‐infested plants. However, for B. brassicae this was only apparent when the plants were placed in clusters. Host‐plant selection by the generalist aphid M. persicae and oviposition preference by the specialist butterfly P. rapae, however, were not significantly influenced by root herbivory. 5. The results of this study show that the presence of root‐feeding insects can affect feeding and oviposition preferences of foliar‐feeding insects, even under natural conditions where many other interactions occur simultaneously. The results suggest that root‐feeding insects play a role in the structuring of aboveground communities of insects, but these effects depend on the insect species as well as on the spatial distribution of the root‐feeding insects.