bluuebunny/crossref_metadata_2025 huggingface dataset:
The making of a pest: recruitment of Meligethes aeneus onto oilseed Brassicas
Authors: Hokkanen Heikki M.T.
Published: October 2003

Populations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.
The spatio‐temporal distribution of adult Ceutorhynchus assimilis in a crop of winter oilseed rape in relation to the distribution of their larvae and that of the parasitoid Trichomalus perfectus
Authors: Ferguson A.W. , Klukowski Z. , Walczak B. , Perry J.N. , Mugglestone M.A. , Clark S.J. , Williams I.H.
Published: October 2003

The spatio‐temporal distribution of Ceutorhynchus assimilis Payk. (Coleoptera: Curculionidae) adults caught in a rectangular grid of flight traps in a crop of winter oilseed rape (Brassica napus L.) was mapped and was analysed using Spatial Analysis by Distance IndicEs (SADIE). Their distribution was compared to that of their larvae and that of their parasitoid Trichomalus perfectus (Walker) (Hymenoptera: Pteromalidae) in pods. The distribution of immigrating C. assimilis adults was consistent with their arrival at the crop boundaries and movement within the crop towards its centre. Adult C. assimilis were aggregated at all times, invasion being on two fronts, leading to the formation of two major clusters within the crop. Large areas of the crop remained relatively unpopulated. During the emigration phase, numbers declined simultaneously in all parts of the crop. The distributions of adult and larval C. assimilis and of larval T. perfectus were spatially associated. The distribution of the parasitoid did not show a density dependent relationship with that of its host. We discuss the movements of insects which underlie their population distributions, the value of integrating spatial information into improved management strategies for C. assimilis and the potential for the spatial targeting of insecticides to reduce the amount applied and to conserve T. perfectus.
Host recognition cues of the granary weevil parasitoid Lariophagus distinguendus
Authors: Steidle Johannes L.M.
Published: October 2003

Host recognition was examined in Lariophagus distinguendus (Förster), a parasitoid of larvae of the granary weevil Sitophilus granarius (L.) that live endophytically in wheat grains. On encountering a grain infested with S. granarius, females of L. distinguendus behave in a set sequence. First they show antennal drumming on the grain, second they tap with the tip of the abdomen on the grain surface, third they drill into the grain and then insert their ovipositor. Bioassays revealed that drumming and drilling was stimulated by non‐volatile chemicals present on the grain‐host complex. Host faeces and herbivore damaged grain material stimulated the most activity, followed by artificially damaged grain, and healthy grain. This is the first report on non‐volatile chemicals released from herbivore‐damaged seeds as signals for foraging parasitoids. Volatile chemicals from the faeces alone were not active. Experiments on the use of physical cues revealed that the presence of a three‐dimensional structure increased the response towards chemicals from the faeces. The shape (ovoid or rectangular solid) and colour (brown or white) of the structure had no impact. Thus, physical cues alone were insufficient to stimulate host recognition behaviour, but acted by increasing the response towards the chemical stimuli.
Behavioural observations of Pieris brassicae larvae indicate multiple mechanisms of action of analogous drimane antifeedants
Authors: Messchendorp L. , Gols G.J.Z. , van Loon J.J.A.
Published: October 2003

We tested 11 analogous synthetic drimane antifeedant compounds for their feeding inhibiting effects on larvae of the large white butterfly Pieris brassicae L. (Lepidoptera: Pieridae) in no‐choice tests on the host plant Brassica oleracea L. Furthermore, we observed larval feeding behaviour in no‐choice tests to analyze temporal effects of five drimanes. The results show that the five analogous antifeedants differentially influence feeding behaviour and locomotion activity. Warburganal and polygodial are most likely sensory mediated antifeedants. Habituation to these compounds occurs soon after the onset of the tests (i.e., within 0.5–1.5 h). Compound 5 and confertifolin are probably not direct, sensory mediated antifeedants. After 0.5–1.5 h of exposure, these compounds inhibit not only feeding, but also locomotion behaviour, indicating postingestive, toxic effects. Isodrimenin inhibits feeding from the onset of the test and is probably a sensory mediated antifeedant. No habituation occurs to this compound, indicating that isodrimenin is either a very strong antifeedant or that it additionally has postingestive, toxic effects. Topical application of the drimanes on the larval cuticle revealed feeding inhibiting effects, but these could not be related to the occurrence of postingestive feeding inhibiting effects, indicating that this method is inappropriate to show possible postingestive effects of drimanes in P. brassicae. In conclusion, the behavioural observations performed in this research indicate that analogous drimanes inhibit feeding by P. brassicae larvae through multiple mechanisms of action. The results show that, when developing a structure activity relationship (SAR) for a series of antifeedants, it is important to distinguish the mode of action which underlies inhibition of feeding.
Selection of hibernation sites by Anthonomus pomorum: preferences and ecological consequences
Authors: Toepfer St. , Gu H. , Dorn S.
Published: October 2003

The apple blossom weevil, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), has a long period of aestivo‐hibernation in the adult stage lasting from summer to early spring of the following year. Potential hibernation sites within an apple orchard consist of high‐stem rough‐bark trees or dwarf smooth‐bark trees. Field release‐recapture experiments in 2 consecutive years showed that 64 and 47% of the weevils remained in the vicinity of the release sites in an area of high‐stem trees and dwarf trees, respectively. The dispersing weevils moved over an average distance of 5.5 m in the dwarf tree area, as compared to 3.8 m in the high‐stem tree area. The prevalent direction of dispersal was along tree rows in both areas. Some weevils displayed, after release in mid‐July, a directional dispersal to the adjacent forests. Others, released in the dwarf tree area, dispersed towards the area of high‐stem rough‐bark apple trees. Experiments simulating various hibernation sites demonstrated that the litter of dry leaves was the most preferred overwintering shelter, yielding a relatively high survival rate. Branches with rough bark ranked second, while branches with smooth bark, grass and pure soil were not favourable for overwintering. Flight tendency in newly emerged weevils of summer generation was significantly higher in June/July than in August/September. This corresponds to the dispersal behaviour in the field. The timing of spring colonisation of apple trees was similar for weevils overwintering within the orchard and for those from outside. These results suggest that modern, dwarf apple orchards offer unfavourable conditions for overwintering, but that the relatively small proportion of weevils which manage to reach the adjacent forests find optimal hibernation sites there.
Genetic, biochemical, and behavioral uniformity among populations of Myzus nicotianae and Myzus persicae
Authors: Clements Kieran M. , Sorenson Clyde E. , Wiegmann Brian M. , Neese Paul A. , Roe R. Michael
Published: October 2003

Prior to designation as distinct species, an appellation presently in question, the tobacco aphid, Myzus nicotianae Blackman (Homoptera: Aphididae), was classified as a tobacco‐feeding form of the green peach aphid, Myzus persicae (Sulzer). In this study, RAPD polymorphisms distinguished members of the Myzus persicae complex (M. persicae and M. nicotianae) from three outgroup Myzus species (M. cerasi (F.), M. hemerocallis Takahashi, and M. varians Davidson). Polymorphisms within the complex did not separate populations on the basis of host association (tobacco versus other host plants) or geographic origin (collections from the United States, Europe, and Japan). Similarly, while GC‐MS analysis of cuticular hydrocarbon profiles revealed both developmental and inter‐populational differences within the M. persicae complex, it did not separate populations of tobacco feeding aphids from those collected off non‐tobacco hosts. Finally, with the exception of their responses to a choice between lettuce and collards, the host preference behavior of a green peach aphid population, a red tobacco aphid population, and a green tobacco aphid population was indistinguishable in host preference experiments. These results add to a growing body of evidence suggesting M. nicotianae and M. persicae are conspecific.
Flower preference behaviour of western flower thrips in the Similkameen Valley, British Columbia, Canada
Authors: Pearsall Isobel A.
Published: October 2003

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), occur on most wildflowers, weed and ground cover flowers in the southern interior of B.C., Canada. Preference by WFT for naturally occurring ground cover blooms was determined in a series of choice trials aimed to examine the potential of using such flowers as trap crops under nectarine trees. The effect of height of flowers above ground level within an orchard was also examined to determine whether this may affect flower attractiveness. Although WFT showed consistent preferences for various flower types, no ground cover grown presently in this region appeared to have potential as an effective trap crop. The density of WFT landing on less preferred flower types was not reduced when more attractive flowers also were present, and WFT were found to distribute evenly over all flowers available. Western flower thrips responded to the density of flowers only in response to highly scented flowers, and were attracted equally to mixtures of colours and single colours of flowers. There was a consistent preference by WFT in the spring for flowers located at ground level.
Fitness effects of two facultative endosymbiotic bacteria on the pea aphid, Acyrthosiphon pisum, and the blue alfalfa aphid, A. kondoi
Authors: Chen De‐Qiao , Montllor Clytia B. , Purcell Alexander H.
Published: October 2003

The effects of two bacterial endosymbionts, designated PASS and PAR, were evaluated on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera:Aphididae), in which they occur facultatively, and on the blue alfalfa aphid, A. kondoi Shinji, in which these bacteria have not been found in natural populations. Subclones of pea aphids and blue alfalfa aphids, derived from parent aphid clones that did not contain PASS or PAR, were infected with one or both bacteria, generating PASS‐ and/or PAR‐positive subclones with minimal genetic differences from the parent clones. Under laboratory conditions at 20 °C, PAR consistently reduced the fecundity (by between 19 and 60%) of subclones derived from three different parent pea aphid clones on bur clover, Medicago hispida Gaertn. PAR had intermediate effects on pea aphids reared on sweet pea, Lathyrus odoratus L., and had no significant effect on pea aphids on alfalfa, Medicago sativa L. The effect of PASS was either neutral or negative, depending on parent clone as well as host plant. Also at 20 °C, PASS reduced fecundity (70–77%) and longevity (40–48%), and increased the age of first reproduction (by up to 1.5 days) of blue alfalfa aphid reared on alfalfa and clover. PAR had a less dramatic effect (e.g., 30–39% reduction in fecundity) on these traits of blue alfalfa aphid. In contrast, PAR and PASS increased the fitness of pea aphid subclones of one parent clone reared for three generations at 25 °C on each of the three test plants. Without facultative bacteria, fecundity of the parent clone was reduced to a mean total of < 6 offspring per adult at this elevated temperature, but with PASS or PAR, mean total fecundity of its subclones was > 35. However, this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived subclones. Alate production in pea aphids was significantly increased in large populations of two PASS‐ and PAR‐positive subclones relative to their parent clones. Attempts to transmit PASS or PAR horizontally, i.e., from aphid to aphid via feeding on host plants (bur clover), were unsuccessful.
A natural flightless mutation in the ladybird, Harmonia axyridis
Authors: Tourniaire R. , Ferran A. , Giuge L. , Piotte C. , Gambier J.
Published: October 2003

A homozygous flightless strain, obtained by selection from a laboratory population of Harmonia axyridis Pallas (Coleoptera, Coccinellidae), has been reared under controlled conditions since 1982 after sampling in China. The adults of this flightless strain have normal elytra and wings but drop almost vertically when they attempt to fly. The origin of this mutation, whether laboratory or natural, is discussed. As the mutation does not affect the fitness of the beetles, this flightless strain can be used in biological control. Releasing flightless adults rather than larvae should provide the potential for more continuous control of aphids by both larvae and adults.
Specificity of constitutive and induced resistance: pigment glands influence mites and caterpillars on cotton plants
Authors: Agrawal Anurag A. , Karban Richard
Published: October 2003

Cotton plants contain suites of phytochemicals thought to be important in defense against herbivores, some of which are localized in pigment glands which contain gossypol and other terpenoid aldehydes. The simple genetic basis for the expression of these glands has led to the development of near‐isogenic glanded and glandless genotypes. Glands may also be phenotypically induced by herbivory. We determined the consequences of constitutive and induced gland expression on two types of herbivores, spider mites (cell content feeders) and noctuid caterpillars (leaf chewers).

Induction of glands was strongly dependent on the density of attackers. Spider mite herbivory on cotyledons (1) increased the density (but not total number) of glands on cotyledons linearly, (2) increased the density and total number of glands on the first true leaf linearly, and (3) affected the density and total number of glands on the second true leaf non‐linearly, compared to controls. Neither constitutive nor induced expression of glands affected mite population growth. An equal reduction of mite population size on induced glanded and glandless plants (50%) relative to uninduced controls indicated that factors other than glands were associated with induced resistance to mites. Constitutive gland expression had a strong negative impact on caterpillar performance, reducing growth by 45%. Induced resistance to caterpillars was three times stronger in glanded genotypes than in glandless genotypes, indicating that factors associated with induced resistance to caterpillars are strongly associated with glands. Three cotton varieties were highly variable in their constitutive and induced resistance to mites and caterpillars.

Thus, defense of cotton plants against herbivores can be roughly categorized as constitutive and inducible factors associated with terpenoid aldehyde containing pigment glands that are effective against caterpillars, and factors not associated with glands that are effective against mites.
Orientation behaviour of the predatory hemipteran Perillus bioculatus to plant and prey odours
Authors: van Loon Joop J.A. , de Vos Eline W. , Dicke Marcel
Published: October 2003

The pentatomid predator P. bioculatus responded by positive odour‐conditioned anemotaxis when exposed to airborne volatiles emitted by potato plants damaged by Colorado potato beetle larvae, whereas intact potato plants and non‐feeding larvae as odour sources failed to elicit anemotaxis. Walking tracks of adult predators had higher values of straightness and upwind fixation when odours emanating from mechanically damaged plants were encountered than tracks registered in response to air carrying volatiles from intact plants, but these parameters returned to control values within 1–2 h after damage was caused. In contrast, air led over plants damaged by beetle larvae elicited orientation responses at least 3 hours after feeding damage ceased. The combination of chemical data on headspace composition, olfactory sensitivity established in electro‐antennogram studies and behavioural data presented here imply a role of sesquiterpenoid plant volatiles as odorous cues eliciting attraction of this predator to damaged potato plants.
Physical features of grass leaves influence the placement of eggs within the plant by the Hessian fly
Authors: Kanno H. , Harris M.O.
Published: October 2003

Hessian fly eggs are more likely to be found on adaxial rather than abaxial surfaces of wheat leaves. These leaf surfaces differ in their physical features: the adaxial side of the leaf has parallel grooves and ridges while the abaxial side is relatively smooth. We used leaf models to investigate the relationship between Hessian fly egglaying and these physical features. When both sides of a green paper leaf model were treated with a wheat leaf extract, but only one side of the model was scored with parallel grooves, the grooved side received more eggs than the smooth side. As the number of grooves per surface increased from 0 to 10, eggs per model increased. When grooves and the wheat leaf extract were tested together and separately, the grooves significantly increased egg numbers in the presence, but not the absence, of wheat extract. In contrast, wheat extract increased egg numbers both in the absence and presence of grooves. Molding techniques were used to recreate the physical features of the adaxial and abaxial leaf surfaces of five grasses. For four of the grass genotypes (a triticale, two common wheats, and a durum wheat), patterns of egglaying on real leaves and molded models were similar, i.e., adaxial leaf surfaces and adaxial molded models were preferred over abaxial leaf surfaces and abaxial models. On the fifth grass, oat, preferences for the adaxial side of real leaves and for adaxial models were not as obvious. We conclude that the adult female Hessian fly obtains information about the leaf surface through her tactile and/or kinesthetic senses and uses this information when making egglaying decisions.
Host‐plant selection by insects – a theory based on ‘appropriate/inappropriate landings’ by pest insects of cruciferous plants
Authors: Finch S. , Collier R.H.
Published: October 2003

Seven hypotheses, including the ‘Resource Concentration Hypothesis’ and the ‘Enemies Hypothesis’, have been put forward to explain why fewer specialist insects are found on host plants growing in diverse backgrounds than on similar plants growing in bare soil. All seven hypotheses are discussed and discounted, primarily because no one has used any of them to produce a general theory of host plant selection, they still remain as hypotheses. However, we have developed a general theory based on detailed observations of insect behaviour. Our theory is based on the fact that during host plant finding the searching insects land indiscriminately on green objects such as the leaves of host plants (appropriate landings) and non‐host plants (inappropriate landings), but avoid landing on brown surfaces, such as soil. The complete system of host plant selection involves a three‐link chain of events in which the first link is governed by cues from volatile plant chemicals, the central link by visual stimuli, and the final link by cues from non‐volatile plant chemicals. The previously ‘missing’ central link, which is based on what we have described as ‘appropriate/inappropriate landings’, is governed by visual stimuli. Our theory explains why attempts to show that olfaction is the crucial component in the central link of host plant selection proved intractable. The ‘appropriate/inappropriate landings’ theory is discussed to indicate the type of work needed in future studies to improve our understanding of how intercropping, undersowing and companion planting can be used to optimum effect in crop protection. The new theory is used also to suggest how insect biotypes could develop and to describe why pest insects do not decimate wild host plants growing in ‘natural’ situations.
Genetic analysis of resistance to azinphosmethyl in the pear psylla Cacopsylla pyri
Authors: Buès R , Toubon J.F. , Boudinhon L.
Published: October 2003

Laboratory selection with azinphosmethyl had little effect on the chemical resistance in Cacopsylla pyri strains, in comparison to the original wild populations. The resistance ratio relative to a susceptible strain varied from 10‐ to 40‐fold depending on the generation studied. Crosses between two resistant strains and the susceptible strain show resistance to be autosomally inherited and semi‐dominant in expression. Backcrosses between F1 and the susceptible strain were unable to distinguish unabigously between monogenic and polygenic inheritance. In the majority of experiments, however, the overall dose‐response relationship for backcross progeny was consistent with a single gene hypothesis. Additional bioassays showed azinphosmethyl‐resistant strain to cross‐resistant monocrotophos and phosmet, but not carbamates, pyrethroids, amitraz or the organophosphates chlorpyrifos and mevinphos.
Life history comparison between two competitive Aleochara species in the cabbage root fly, Delia radicum: implications for their use in biological control
Authors: Fournet S. , Stapel J.O. , Kacem N. , Nenon J.P. , Brunel E.
Published: October 2003

This study evaluates the efficacy of Aleochara bilineata Gyll and Aleochara bipustulata L. (Coleoptera: Staphylinidae) as biological control agents against the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae). Biological and demographic characters are documented and comparisons made between the two species. The following results were obtained:

The reproductive potential and longevity of A. bipustulata females are significantly higher than those of A. bilineata. These differences are correlated with the biology and ecology of the hosts of both species.

Under laboratory conditions the rate of increase (rm) of both staphylinids species is significantly higher than that of the pest and their major competitor Trybliographa rapae West. (Hymenoptera:Figitidae). This may indicate that A. bilineata and A. bipustulata can be effective biological control agents.

Aleochara bilineata appears to be the most interesting biological control agent against D. radicum, because of its higher rate of increase, higher host specificity and host acceptance, and a development time which is well synchronised with that of its host. With its higher competitive ability, a population of A. bilineata may increase even if competition occurs. However, A. bipustulata presents interesting biocontrol characteristics, but the best strategy may be only to use the potential of its natural populations.
The role of chemical cues in host finding and acceptance by Callosobruchus chinensis
Authors: Ignacimuthu S. , Wäckers F.L. , Dorn S.
Published: October 2003

We studied the response of female Callosobruchus chinensis to chemical cues emitted by cowpea seeds at different stages of bruchid infestation (uninfested, egg carrying, L1‐, and L4‐infested). Olfactory attractiveness was determined in Y‐tube olfactometer assays by testing individual seed categories against either clean air or uninfested seeds. Oviposition preferences between uninfested and infested seeds were determined in petri‐dish choice‐experiments. The olfactometer assays revealed that weevils discriminate between seeds containing different stages of developing bruchids on the basis of olfactory cues. While odors from uninfested and egg‐carrying seeds acted as attractants, odors from L1‐ and L4‐infested seeds failed to induce a positive response by the bruchids. When given a choice between uninfested and infested seeds in the olfactometer, weevils preferred uninfested seeds over L1‐ and L4‐infested seeds, but failed to distinguish between uninfested and egg‐carrying seeds. In the oviposition experiment as well, bruchids showed a distinct preference for uninfested seeds when offered in combination with L1‐ and L4‐infested seeds. This experiment further showed a reduced acceptance of egg carrying seeds. Our results indicate that C. chinensis females use chemical information during both host searching and host acceptance. Volatiles from uninfested or egg carrying seeds act as attractants, while deterrence increases as development of bruchid immature stages progresses.
Effects of carbaryl exposure on the last larval instar of Xanthocnemis zealandica– fluctuating asymmetry and adult emergence
Authors: Hardersen Sönke
Published: October 2003

Fluctuating asymmetry (FA), a measure of developmental stability, has been suggested as a monitoring tool for environmental pollution. Aquatic pollution events are often transitional and the level of FA in populations exposed to such incidents has not yet been investigated. Research into the morphological effects of transitional pollution also provides a tool to elucidate the timing and duration of any ‘window of opportunity’ for the determination of FA in the developing organism. The present study was undertaken to investigate if exposure of the last instar of the damselfly Xanthocnemis zealandica (McLachlan) (Zygoptera: Coenagrionidae) to different levels of insecticidal stress resulted in different levels of FA in the wings of the adult insects and if adult emergence was altered by different concentrations of pesticide. Three concentrations of carbaryl (40 ppb, 2 ppb and 0.1 ppb) and a control were used. The emergence success of the damselflies was not affected by any treatment, but the insecticide had a stimulatory effect on the developing larvae. Exposure of the last instar of X. zealandica to carbaryl at 40 ppb had no consistent effect on FA in metric traits and increased FA in meristic traits compared with the control. Segregation of the emerged adults into two groups revealed more details about the ‘window of opportunity’ in the meristic traits. Larvae which had already completed more than half of their development when the experiment started did not show significant differences in the level of FA. In contrast, damselflies which were exposed for more than half of the final instar showed a clear difference in their levels of FA. The greater difference in the latter group was mainly caused by a decrease of FA in the controls rather than by an increase in the treatment. These data suggest that the ‘window of opportunity’ for the determination of the level of FA of the meristic traits in damselfly wings closes approximately halfway through the final larval instar.
Host‐stage selection by Trybliographa rapae, a parasitoid of the cabbage root fly Delia radicum
Authors: Neveu Nathalie , Krespi Liliane , Kacem Nabila , Nénon Jean‐Pierre
Published: October 2003

Host‐stage selection by Trybliographa rapae Westwood (Hymenoptera: Figitidae) was studied in choice and no‐choice experiments in the laboratory. The parasitoid was able to reproduce in first, second, and third instars of the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), but oviposition occurred more frequently in third instars when all three developmental stages were offered simultaneously. Oviposition in third instars increased the rate of development of offspring and their body size, but did not alter sex ratio. Results are discussed in the light of predictions made by the theory of optimal host acceptance.
Realized heritability of behavioral responsiveness to an oviposition deterring pheromone in the azuki bean weevil Callosobruchus chinensis
Authors: Tanaka Yoshinari
Published: October 2003

Artificial selection was conducted to reduce the behavioral responsiveness of female bruchid beetles, Callosobruchus chinensis, to the oviposition deterring pheromone excreted by conspecific females. Significant responses to selection were observed after two generations of selection. Realized heritability was estimated as 0.052 ± 0.017 from cumulative responses regressed on cumulative selection differentials. These results indicate that this pheromone communication system has significant additive genetic variance needed for its evolution.
Host regulation by the aphid parasitoid Aphidius ervi: the role of teratocytes
Authors: Falabella Patrizia , Tremblay Ermenegildo , Pennacchio Francesco
Published: October 2003

The biochemical profile and metabolism of Acyrthosiphon pisum (Harris) (Homoptera, Aphididae) are markedly altered and redirected in response to parasitization by the endophagous braconid Aphidius ervi Haliday (Hymenoptera, Braconidae). In the present study, the role played in the host regulation process by teratocytes, cells deriving from the dissociation of the embryonic membrane of the parasitoid, is taken into consideration. The protein synthesis activity of these cells of embryonic origin is analysed in vitro and an essential characterization of those proteins de novo synthesized and released in the incubation medium is provided. Teratocytes, obtained by dissecting parasitized host aphids, 3, 4 and 5 days after parasitoid oviposition, were incubated in vitro and, at the end of the incubation period, were separated from the medium for SDS‐PAGE analysis of both cellular and secreted proteins. Various cellular proteins were more abundant as the time between parasitization and teratocyte collection increased. Furthermore, two proteins, showing an approximate molecular mass of 15 kD (p15) and 45 kD (p45) respectively, were abundantly secreted in the incubation medium by 5 day‐old teratocytes. Incubations in presence of 35S radiolabelled amino acids indicated that p15 and p45 are both synthesized by A. ervi teratocytes. The amino acid composition of these two proteins was similar to that reported for other insect proteins with a demonstrated nutritional function. The p45 protein was found to be glycosylated. A tentative physiological model describing the host regulation role played by different parasitoid‐derived factors is proposed.
The role of plant chemical cues in determining host preference in the generalist aphid parasitoid Aphidius colemani
Authors: Storeck A. , Poppy G.M. , van Emden H.F. , Powell W.
Published: October 2003

The host preference behaviour of the generalist aphid parasitoid Aphidius colemani was investigated using a Y‐tube olfactometer. Female A. colemani showed a preference for the host‐plant complex on which they had been reared, even though the same aphid host was involved, demonstrating a host plant preference. This preference was not evident when the parasitoids were dissected from their mummies prior to adult emergence. Host plant preference exhibited during host selection appeared to be induced by chemical cues encountered on the mummy case at the time of emergence, but preferences could be changed by subsequent foraging experiences. It is concluded that plant chemical cues play a major role in determining initial preferences through a process of emergence conditioning but that learning processes, involving cues encountered during oviposition in or contact with the host, can modify these initial preferences.
Influence of host distribution on foraging behaviour in the hyperparasitoid wasp, Dendrocerus carpenteri
Authors: Chow Andrew
Published: October 2003

The foraging behaviour of Dendrocerus carpenteri Curtis (Hymenoptera: Megaspilidae), an ectophagous hyperparasitoid of aphidiine wasps inside mummified aphids, was examined in the laboratory with an experimental system consisting of broad bean, Vicia faba L, the pea aphid, Acyrthosiphon pisum Harris, and a primary parasitoid, Ephedrus californicus Baker. Pea aphids parasitised by E. californicus often disperse from their feeding sites (or off host plants) before dying and mummifying. Response of female hyperparasitoids to host distribution was evaluated at two spatial scales. At the first scale, behaviour of hyperparasitoids was examined on individual plants with different densities of hosts. At the second scale, habitat complexity and host location were manipulated in large foraging cages containing several plants. I show that patterns of density‐dependent hyperparasitism can result from the foraging behaviour of D. carpenteri. However, dispersal of parasitised aphids may not reduce the incidence of hyperparasitism if hyperparasitoids systematically search the habitat.
Effects of wax bloom variation in Brassica oleracea on foraging by a vespid wasp
Authors: Eigenbrode Sanford D. , Rayor Linda , Chow Jennifer , Latty Paul
Published: October 2003

Foraging by individual Polistes dominulus (Christ) (Hymenoptera: Vespidae) was observed and compared on Brassica oleracea L. plants that differed in surface wax bloom. Twenty‐six wasps, previously trained to forage on plants for 4th instar Trichoplusia ni (Walker), were presented in the greenhouse with mixtures of plants with normal wax bloom or genetically reduced wax bloom, and on which T. ni caterpillars had been placed. During foraging, the wasps were observed to slip significantly more frequently from the leaf surfaces of normal‐wax bloom plants than from reduced‐wax bloom plants (129 vs 63 occurrences) and to retrieve significantly fewer pieces of caterpillar after attack on normal‐wax bloom plants (151 vs 223 pieces). Altogether the wasps retrieved 333 caterpillar pieces from reduced‐wax bloom plants and 248 pieces from normal‐wax bloom plants. Despite these differences, the number of caterpillars attacked and killed did not differ between the two wax bloom types (116 vs 121), nor did handling time for individual attacks (time from contact with prey until prey piece was carried to the nest) (170±12.5 s vs 180±10.5 s). Thus, in contrast with previous reports for smaller predators, wax bloom variation in B. oleracea did not influence the effectiveness of P. dominulus as a predator of T. ni.
Performance of leaf beetle larvae on sympatric host and non‐host plants
Authors: Ballabeni Pierluigi , Rahier Martine
Published: October 2003

Studies asking the ability of insects to utilize novel host plants often use novel hosts that are allopatric with the insect population under investigation. However, since the outcomes of species interactions are often site‐specific, such studies cannot tell us whether a plant would actually be used by a given insect population if the plant grew sympatrically with it. We therefore performed a quantitative genetics experiment to analyse the performance of larvae of the leaf beetle Oreina elongata Suffrian (Coleoptera: Chrysomelidae, Chrysomelinae) on two host and three non‐host plants, collected from a site where insects and plants co‐occur in the Western Alps. When raised on the non‐host Petasites albus (L.), larvae were able to survive equally well as on the two hosts, Adenostyles alliariae (Gouan) and Cirsium spinosissimum (L.), whereas they did not survive on the two other non‐hosts, Peucedanum ostruthium (L.) and Rumex alpinus L. On P. albus, growth rate was slightly lower and development time slightly longer than on the two hosts. We found a genotype by environment interaction only for growth rate but not for development time and survival. However, the shape of the reaction norms of growth rates suggests that it is unlikely that selection could favour the inclusion of P. albus into the host range of the study population.
Attracticidal spheres for controlling apple maggot flies: commercial‐orchard trials
Authors: Prokopy Ronald J. , Wright Starker E. , Black Jonathan L. , Hu Xing Ping , McGuire Michael R.
Published: October 2003

Wooden pesticide‐treated red spheres and biodegradable sugar/flour pesticide‐treated red spheres were compared with wooden sticky‐coated red spheres and insecticide sprays for controlling apple maggot flies, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), in small blocks of apple trees in Massachusetts commercial orchards in 1997, 1998 and 1999. Pesticide‐treated spheres received a coating of 70% latex paint, 20% feeding stimulant (sucrose), and 10% formulated insecticide (containing 20% imidacloprid). To replenish sucrose lost during rainfall, wooden spheres were capped with a disc comprised of hardened sucrose that seeped onto the sphere surface, whereas the surface of sugar/flour spheres received sucrose that seeped from the interior. Each year, each of the 24 perimeter trees of each non‐sprayed block received a sphere baited with butyl hexanoate (an attractive component of host fruit odor), with the intent of intercepting immigrating flies. Based on captures of flies on unbaited sticky‐coated red spheres placed near the center of each block and on periodic samples of fruit for injury, there was a consistent pattern of treatment performance. Each year, sticky‐coated spheres were only slightly less effective than two or three sprays of organophosphate insecticide, sugar/flour pesticide‐treated spheres were only slightly less effective than sticky spheres, and wooden pesticide‐treated spheres were least effective. Versions of pesticide‐treated spheres used in 1999 were more durable than those used in previous years, but further improvement is needed before either wooden or sugar/flour pesticide‐treated spheres can be recommended for grower use.
Oviposition behaviour, influence of experience on host size selection, and niche overlap of the solitary Leptomastix epona and the gregarious Pseudaphycus flavidulus, two endoparasitoids of the mealybug Pseudococcus viburni
Authors: Karamaouna Filitsa , Copland Michael J.W.
Published: October 2003

Oviposition behaviour and host size selection of the solitary parasitoid Leptomastix epona (Walker) and the gregarious Pseudaphycus flavidulus (Brèthes) [both Hymenoptera: Encyrtidae] were examined on five size classes of the mealybug Pseudococcus viburni (Signoret) [Hemiptera: Pseudococcidae]. The host size classes mostly consisted of one stage (first, second, third instar nymph, young adult and preovipositing adult) and were presented together to wasps of either parasitoid species. Both parasitoid species locate the host by drumming the surface of the patch with the antennae. Leptomastix epona seems to use mainly the antennae to examine the host but P. flavidulus may accept or reject a host for oviposition after antennation or insertion of the ovipositor. Leptomastix epona attempts oviposition in all the host stages from second instar nymphs but P. flavidulus includes first instar. Both parasitoid species select mainly larger hosts (>1 mm, third instar nymphs) to oviposit but P. flavidulus is able to parasitize more second instar nymphs compared to L. epona. Female wasps of L. epona may host feed on small mealybugs (second and third instar nymphs) that they do not use for oviposition. Oviposition experience of either parasitoid species for 24 hours does not influence host size selection on patches with hosts of similar mixed sizes. Oviposition decisions are independent of the host sizes of the preceding ovipositions. Implications about stability of a single parasitoid – host system and the success of biological control of the mealybug were discussed in respect of the developmental refugia of the two parasitoid species. Niche overlap of the two parasitoid species was discussed with a view to giving an insight into a single or multiple introduction.
Vacuuming tarnished plant bug on strawberry: a bench study of operational parameters versus insect behavior
Authors: Vincent Charles , Chagnon Roger
Published: October 2003

A vacuum apparatus was used in a test bench environment to determine the effects of two operational parameters on vacuuming efficacy for an insect pest. Nymphs and adults of tarnished plant bug, Lygus lineolaris P. de. B. (Hemiptera: Miridae), marked with fluorescent powder, were positioned on strawberry plants according to three height classes. Three speeds of inlet passage (i.e., 2, 4 and 6 km h−1) and two heights (passage at 2/3 and 3/3 of the canopy) of inlet relative to the top canopy of the plants were investigated. After vacuuming the marked insects remaining on the plants were then found using a UV light and the class height of their position on the plant and the substrate (i.e., soil, leaf, stem or fruit/flower) were noted. The efficacy of the vacuum was optimal when the inlet was passed at 4 km h−1 with the inlet at a height of 2/3 of the strawberry canopy. Nymphs were usually vacuumed more efficiently than adults. Most (64.5%) individuals that were not vacuumed did not change position after inlet passage. Most (85.9%) individuals that changed position after inlet passage experienced vertical, mostly downward, movements.
The influence of host plant species on parasitism of pollen beetles (Meligethes spp.) by Phradis morionellus
Authors: Billqvist Andreas , Ekbom Barbara
Published: October 2003

Field experiments were conducted at Ultuna in central Sweden in order to determine if parasitism of pollen beetle larvae (Meligethes aeneus Fabr. and Meligethes viridescens Fabr. (Coleoptera: Nitidulidae)), by Phradis morionellus Holmgr. (Hymenoptera: Ichneumonidae) differed between the host plants spring rape, Brassica napus L., and white mustard, Sinapis alba L. Parasitism by P. morionellus varied between 25% and 53%. There was no consistent difference between proportion parasitism on the two host plant species among the four studied fields. There was a significantly higher risk of parasitization on S. alba than on B. napus in two fields. The opposite occurred in a third field and in a fourth field no difference between parasitism on plant species was found. Density of host larvae affected parasitization by P. morionellus on B. napus, with lower parasitism at higher pollen beetle densities. The next most common parasitoid species, after P. morionellus, encountered on pollen beetle larvae was Diospilus capito Nees (Hymenoptera: Braconidae). The level of total parasitism by these two species was between 31% and 66%. Interspecific competition of P. morionellus with D. capito through multiparasitism was independent of both field location and plant species. The level of multiparasitism was, in all cases, less than 6.3%.
Detection of stored‐wheat beetle species and estimation of population density using unbaited probe traps and grain trier samples
Authors: Athanassiou C.G. , Buchelos C.T.
Published: October 2003

Field studies were conducted in order to compare the effectiveness of unbaited probe traps and grain trier samples in the detection of several beetle species. On June 15, 1997, fourteen probe traps were placed in three steel bins containing wheat in Central Greece. Two of them were inserted in the central zone of the bulk, five in the half of the bin radius (median zone) and seven near the bin wall (distal zone). From June 30 up to and including January 1998, the traps were checked for adult beetles every fifteen days (15 sampling dates in total). On each date, samples were also taken from spots adjacent to trap locations, using a grain trier. The mean temperatures recorded near the bulk surface decreased by an average of 1.16 °C per sampling date. Twenty‐four species, belonging to 14 families of Coleoptera were found. The most abundant species in the traps were Cryptolestes ferrugineus and Tribolium castaneum, while Sitophilus oryzae was the most abundant in the samples. Significantly greater numbers of adults were found in traps than in samples, during the whole sampling period; traps also detected adults in most locations while in the corresponding samples no adults were found. Significantly higher numbers of adults were found in the central sampling zone, using both devices. Taylor's power law parameters showed that in both sampling methods the most abundant species showed aggregated spatial patterns. Although the correlation coefficient values between trap catches and number of adults per trier sample differ significantly from zero (P < 0.01) in a high number of sampling dates, it can be concluded that traps are poor indicators of population density. The accuracy provided as a percentage of the mean, decreases exponentially with the increase of the mean value. Based on traps, the desired accuracy level (35%) is not achievable even in higher mean values or even with high numbers of traps. On the contrary, with trier samples it is possible to estimate population density with a relatively low number of sampling units. Significant differences in the required number of sampling units (sample size) were noted among species.
Developmental polymorphism: a major factor for understanding sublethal effects of Bacillus thuringiensis
Authors: Moreau Gaétan , Bauce Éric
Published: October 2003

Developmental polymorphism in Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) was induced by Bacillus thuringiensis (Berliner) in the laboratory. The B.t. formulation concentration induced a quadratic response on the incidence of developmental polymorphism. A double application of Bacillus thuringiensis at fourth and fifth instar respectively resulted in a higher occurrence of developmental polymorphism than a single application at fifth instar. Smaller larval weight prior to B.t. exposure resulted in higher incidence of developmental polymorphism. However, larvae exhibiting developmental polymorphism exhibited larger pupae and an extended larval period. Thus, developmental polymorphism and Bacillus thuringiensis ingestion together prolonged the development time but induced opposite effects on pupal weight. These findings suggest that the calculation of sublethal effects on pupal weight and development time that include developmental polymorphism as an uncontrolled source of variation could lead to an inadequate understanding of insect response in any stress‐induced experiments.