bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensity and spectral emission as factors affecting the efficacy of an insect electrocutor trap towards the house‐fly
Authors: Roberts A. E. , Syms P. R. , Goodman L. J.
Published: April 2011

Competitive tests were used to determine how the quantitative and spectral characteristics of an electrocutor trap light source affected the attraction of the house‐fly, Musca domestica L. It was found that an increase in the radiant flux (Fe) of the trap lamps due to an increase in radiant area (A), caused a much larger increase in catch than if radiant flux was increased through higher radiant emittance (Me). The results from electroretinograms recorded in response to different levels of Me were consistent with the idea that at a given wavelength the attractiveness of a lamp is attributable to the quantitative output perceived by the fly. Of nine fluorescent lamps, the most attractive had peak emission at 340 nm. A blue lamp (peak emission 419 nm) attracted less than a third as many flies as the UV emitting lamps, and a white lamp (peak emission 585 nm) attracted fewer than a quarter as many. The corresponding photoreceptor responses were measured using the electroretinogram. At wavelengths above 400 nm the attractiveness of a lamp to a fly appears to be lower relatively than the photoreceptor response. Within the ultraviolet region (300 nm–400 nm) attractiveness is again attributable to the quantitative output perceived by the fly. It is concluded that there is a genuine behavioural preference for lamp emissions in the ultraviolet region.
Inducing the sexual forms and hatching the eggs of pea aphids
Authors: Via S.
Published: April 2011

In temperate climates, pea aphids (Acyrthosiphon pisum) produce a single sexual generation each year in response to declining photoperiod and temperature. Mating occurs in the fall and the eggs have an obligatory winter diapause. Genetic recombination during the sexual phase is thought to be an important source of genetic variability within cyclically parthenogenetic aphid populations. Methods for reliably producing sexual forms and hatching the eggs of aphids are therefore central not only to the study of evolutionary change in aphid populations, but also for a general understanding of the origin of agriculturally important variation in destructiveness within pest species.

Here, sexual forms of six pea aphid clones were induced in the laboratory and eggs were successfully hatched by creating conditions that closely mimicked those found in field situations. A declining photoperiod was produced by controlling artificial lighting using a timer with variable cycle length. Using these conditions, sexual forms were successfully produced for all six clones tested, which were then mated in all combinations. Eggs were exposed to a daily cycle of freezing and thawing in an incubator under a short‐day photoperiod. Egg hatch averaged 60%, but was as high as 89% for some crosses. These methods will permit testing of evolutionary hypotheses and execution of detailed genetic studies of sources of variability within pea aphid populations. They are thus important tools for both evolutionary and agricultural studies.
Diet, fecundity and egg size in some polyphagous predatory carabid beetles
Authors: Wallin H. , Chiverton P. A. , Ekbom B. S. , Borg A.
Published: April 2011

Egg size was measured at different rates of egg laying in three polyphagous carabid species, known to be useful predators of cereal aphids; the small Bembidion lampros Herbst and the medium‐sized Pterostichus cupreus L. and P. melanarius Illiger. Variations in fecundity, as well as the ability of the medium‐sized species to also build up fat reserves, were obtained when beetles were subjected to different dietary regimes consisting of aphids, or foods with a lower or higher protein content. Egg size was found to be dependent on the rate of egg laying within a species. A diet of cereal aphids appeared to be adequate for egg production in these polyphagous carabids, but female P. cupreus were unable to build up fat reserves when they ingested aphids contaminated with the aphicide pirimicarb. Beetles were able to devote resources to more and larger eggs (B. lampros), or to larger eggs and/or fat reserves (P. melanarius/P. cupreus) when given access to a carbohydrate‐rich food with low protein content. The highest rate of egg laying was obtained when female P. cupreus and P. melanarius were given a more varied diet at frequent intervals; including regular shifts between unsprayed aphids, carbohydrate‐rich food and protein‐rich maggots. Within the varied diet treatment a negative relationship was obtained between egg size and egg number among similar‐sized individuals of P. cupreus and P. melanarius; females producing the largest number also laid the smallest eggs. Egg size affected larval survival, since first instars hatching from large eggs were found to survive longer than those hatching from small eggs. The influence of differences in food intake on reproduction, maintenance metabolism, and survival of field‐inhabiting carabids is discussed.
Antiinsectan properties of a novel Fusarium‐derived sterol sulfate
Authors: Dowd P. F. , Burmeister H. R. , Vesonder R. F.
Published: April 2011

The antiinsectan properties of the Fusarium graminearum‐derived novel sterol sulfate, 4, 4, 24‐trimethylcholesta‐8, 14, 24(28)‐trien‐2α, 3β, 11α, 12β‐tetrol 12 acetate, 3‐sulfate were tested on the corn ear‐worm (Heliothis zea (Boddie), the fall armyworm (Spodoptera frugiperda (J. E. Smith), and the driedfruit beetle (Carpophilus hemipterus L.). The sterol sulfate could not be used as a sterol source by any of the insects. The sterol sulfate inhibited growth of S. frugiperda and C. hemipterus larvae at 2500 and 4000 ppm, respectively. Defensive implications of this compound are discussed.
Physical and chemical factors influencing landing and oviposition by the cabbage root fly on host‐plant models
Authors: Košťál V.
Published: April 2011

Various plant models were used in both choice and no‐choice tests in the laboratory to assess landing and oviposition preferences of the cabbage root fly, Delia radicum (L.). The main factor governing the site most suitable for landing was the conspicuousness of the object and not its shape. Oviposition was influenced considerably by the pre‐conditioning of the females. Deprived females laid eggs even when denied access to both host plant chemicals and host‐plant models. The dominant role of contact chemical stimuli in host acceptance was reconfirmed, but only a combination of physical and chemical stimuli appeared capable of eliciting normal oviposition. The combination of contact chemical stimuli and the presence of a stem on the test model had a synergistic effect on the numbers of eggs laid in both choice and no‐choice situations. In choice bioassays, female cabbage root flies distinguished between models of different shapes, heights and sizes. The size and shape of the models appeared to be perceived in part after the flies had landed.
The effect of pre‐acquisition starvation on aphid transmission of potyviruses during observed and electrically recorded stylet penetrations
Authors: Powell G.
Published: April 2011

The effect of pre‐acquisition starvation on stylet penetration behaviour by the aphid Myzus persicae (Sulz.) and the consequent non‐persistent transmission of the potyviruses beet mosaic virus (BMV) and potato virus Y (PVY) were investigated. Visual observations indicated that starved aphids initiated penetrations earlier and penetrated for shorter periods than non‐starved insects. Tethering with a fine gold wire did not affect these observations with either starved or non‐starved aphids, but starvation caused increased PVY and BMV acquisition efficiency, regardless of tethering. Tethered aphids were then made part of an electrical circuit and their stylet activities investigated in detail. Electrically recorded aphids also acquired and inoculated both potyviruses more efficiently when starved, and these acquisitions and inoculations were associated with stylet punctures of plant cell membranes. However, starvation did not affect the occurrence of electrically recorded membrane puncture, suggesting that non‐behavioural factors may contribute to the enhancement of virus transmission by pre‐acquisition starvation.
Electronically monitored feeding behaviour of the lettuce root aphid (Pemphigus bursarius) on resistant and susceptible lettuce varieties
Authors: Cole Rosemary A. , Riggall Wendy , Morgan Alan
Published: April 2011

Feeding behaviour of the lettuce root aphid Pemphigus bursarius was monitored electronically on six lettuce varieties. Aphids, monitored for a minimum of 5 h on lettuce roots, performed recognizable feeding behaviour on the susceptible varieties, Webbs Wonderful and Borough Wonder including non probing, pattern A start of new penetration, C (stylet pathway activities) sometimes including clear B‐waves (salivary sheath secretions), potential drops (intracellular penetrations), intracellular E (phloem ingestion) distinguishing E1 and E2 (Tjallingii, 1990) and occasionally xylem ingestion. Although aphid probing was recorded on the resistant varieties Lakeland and Grand Rapids continued penetration to the phloem elements was deterred and the time spent ingesting phloem was short. Aphids rarely probed the resistant varieties Avoncrisp and Avondefiance and all attempted penetrations quickly terminated.
Tissue localisation of lettuce resistance to the aphid Nasonovia ribisnigri using electrical penetration graphs
Authors: van Helden Maarten , Tjallingii W. F.
Published: April 2011

Electrical penetration graphs (EPG's) of Nasonovia ribisnigri (Mosley) (Homoptera, Aphididae) on resistant and susceptible lettuce (Lactuca sativa, Compositae) showed a large reduction in the duration of the food uptake pattern (E2) on the resistant line. No differences in EPG's were observed before the phloem was reached. Therefore, resistance is believed to be located in the phloem vessel. Both mechanical blocking of the sieve element after puncturing and a difference in composition of the phloem sap are possible resistance factors. However, a chemical factor seems more likely because of the specificity of the resistance against N. ribisnigri.
Carabid beetle assemblage under diversified agroecosystems
Authors: Athayde Tonhasca Jr.
Published: April 2011

Corn (Zea mays L.) and soybean (Glycine max Merrill) were planted in monoculture and strip‐intercropping plots (18.3 times 15.5 m each) under conventional tillage and no‐tillage to create differences in habitat structure. The effects of these agronomic practices on carabid beetle species composition were measured by pitfall‐trap collections during three years. Although neither the number of individuals or number of species were significantly affected by treatments, analyses of variance indicated that four of the six dominant species (75.7% of the total number of carabids captured in three years) responded to tillage treatments. Harpalus pensylvanicus DeGeer and Cyclotrachelus sodalis (LeConte) were more abundant in no‐tillage plots, whereas Pterostichus chalcites Say and Scarites substriatus Haldeman were more common in conventional tillage plots. Pterostichus chalcites was also significantly more abundant in soybean plots than in intercropping or corn plots. H. pensylvanicus, a primarily herbivorous carabid, was the most common species collected. However, P. chalcites, a predaceous carabid, was the dominant species in soybean/conventional tillage plots. The results suggest that characteristics of individual species should be carefully considered for studies of communities such as carabid beetles, which have few strongly dominant species and a wide range of resource utilization.
Host selection and survival of the parasitoid Encarsia formosa on greenhouse whitefly, Trialeurodes vaporariorum, in the presence of hosts infected with the fungus Aschersonia aleyrodis
Authors: Fransen Joanne J. , van Lenteren Joop C.
Published: April 2011

Successful control of greenhouse whitefly may be achieved by complementary activity of the parasitoid Encarsia formosa and the fungus Aschersonia aleyrodis. One way to obtain an additive mortality effect of both entomopathogen and parasitoid would be achieved by the selection of healthy hosts by the parasitoid and rejection of fungus‐infected hosts. Third and fourth instar larvae of Trialeurodes vaporariorum which had been treated with a spore suspension of A. aleyrodis 0, 4, 7, 10 or 14 days beforehand, were presented to female parasitoids. The parasitoids adopted the oviposition posture on untreated hosts as well as on treated hosts, irrespective of the different stages of infection in the hosts. However, significantly more hosts were parasitized by E. formosa in the control treatment than in the fungal treatment. The parasitoids offered treated hosts, showed rejection behaviour after probing on hosts showing detectable signs of infection (containing hyphal bodies or mycelium in the haemolymph). For instance, when hosts were offered seven days after spore treatment, the parasitoids showed an oviposition posture on a total of 83 (95.4%) out of 87 infected larvae, but laid only 4 eggs (4.6%). In contrast, on 48 (94.1%) out of 51 noninfected (or showing no detectable signs of infection) hosts an oviposition posture was adopted and 40 eggs (78.4%) were found after dissection. When infected hosts were encountered the oviposition posture lasted less than 1′40″ while rejection of non‐infected hosts occurred after more than 1′40″. Other experiments were carried out offering treated hosts for 24 h to the parasitoids. The hosts were dissected afterwards. Again, significantly more eggs were laid in the non‐infected hosts. When hosts were parasitized shortly after fungal spore treatment they were colonized by the fungus and the parasitoids did not develop. Transmission of the entomopathogen after probing infected hosts was observed to a limited extent. In conclusion, A. aleyrodis and E. formosa can be used together in a glasshouse situation. The parasitoid will be most effective when introduced more than seven days after application of A. aleyrodis, because from that time onwards it is able to detect and reject fungus‐infected hosts.
Further comments on analysis of covariance in insect dietary studies
Authors: Horton David R. , Redak Richard A.
Published: April 2011

Raubenheimer & Simpson (1992) recently discussed the advantages of using analysis of covariance in insect dietary studies as an alternative to the more conventional ratio‐based nutritional indices. We expand on some interpretations of Raubenheimer & Simpson and illustrate our points with examples from published and unpublished data sets. Specifically, we show that an ANCOVA on biomass gain incorporating initial biomass as a covariate provides information not immediately available using the analysis suggested by Raubenheimer & Simpson (ANCOVA on final biomass incorporating initial biomass as a covariate). Second, we show that dietary studies in which the covariate (food consumption) is affected by diet can provide information about the relative importance of preingestive effects (e.g., deterrence) and postingestive effects (e.g., antibiosis) on performance. Cautions about this latter use of ANCOVA are discussed.
Influence of background on host‐plant selection and subsequent oviposition by the cabbage root fly (Delia radicum)
Authors: Kostal V. , Finch S.
Published: April 2011

The behaviour of female cabbage root flies during host plant selection was studied in the laboratory using brassica plants growing in backgrounds of bare soil, clover, grass, peas and four non‐living materials. Gravid females landed about twice as often on brassica plants growing in bare soil than on comparable plants growing amongst non‐host plants. Once a receptive female landed on a brassica plant, the female made, on average, four ‘spiral flights’ and two jumps on and off the plant before laying alongside the plant. Surrounding a brassica plant with a diverse background altered the behaviour of the flies, so that the spiral flights around the host plant were replaced by short hops between nearby vertical objects. The loss of contact and recontact with the host plant then prevented the females from accumulating sufficient contacts with the host plant to be stimulated to lay. Spiral flights around host plants appear to determine whether or not flies will lay alongside host plants. Flies in mixed plantings have a reduced rate of settling on the host plant, and a higher rate of locomotion, because they land frequently on non‐host plants. Hence, visual stimuli appeared to have greater effects than chemical or mechanical barriers in deterring flies from laying alongside brassica plants in diverse backgrounds. In ‘choice’ situations, backgrounds of real plants reduced oviposition alongside brassica plants by at least 50%. In ‘no‐choice’ situations, flies laid similar numbers of eggs alongside all brassica plants irrespective of plant background or plant size. If numbers of fly eggs are to be reduced on commercial brassica crops by undersowing the crops with clover, plants growing in bare soil may also have to be included to provide the flies with sites preferred for oviposition.
Flight manoeuvers used by a parasitic wasp to locate host‐infested plant
Authors: Kaiser L. , Willis M. A. , Cardé R. T.
Published: April 2011

Cotesia rubeculaMarshall (Hymenoptera: Braconidae) is a specialist larval parasitoid of the butterflyPieris rapaeL. which itself feeds almost exclusively upon cruciferous plants. Female wasps are attracted to the odour of host‐infested plant (plant‐host complex: PHC) and the probability of flights in a wind tunnel depends on females' prior oviposition experience with the PHC and on the concentration of the PHC odour. This study considers the effect of both factors on characteristics of oriented flight upwind towards the PHC. The flight track parameters that we measured and calculated were not significantly affected by these factors.C. rubeculafemales exhibited high average flight velocity and relatively straight flight tracks. There was a considerable variability between individuals, however, in their odour‐modulated upwind flight tracks. Some females generated a zigzagging upwind flight track similar to those commonly observed from male moths responding to female sex pheromone. Other females flew along a straight track directly upwind. The flight tracks of most female wasps were intermediate between these extremes. The full range of these flight performances was observed to all experimental treatments.
Variation in selected life‐history parameters of the parasitoid wasp, Aphidius ervi: influence of host developmental stage
Authors: Sequeira R. , Mackauer M.
Published: April 2011

We determined the age‐specific fecundity and survival of the solitary parasitoid wasp, Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars of apterous pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): (age 24 h), L2 (48 h), L3 (72 h), and L4 (120 h). Age‐specific survival (lx) and fecundity (mx) differed between parasitoids developing in different aphid instars. The wasps' life‐time reproductive success, as indexed by the intrinsic rate of population increase (rm), varied non‐linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, in A. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade‐offs in resource allocation.
Effect of temperature on development rate and intrinsic rate of increase of Aphis gossypii reared on greenhouse cucumbers
Authors: Kocourek F. , Havelka J. , Beránková J. , Jaroŝik V.
Published: April 2011

Thermal requirements for development and life table statistics of Aphis gossypii Glover (Homoptera, Aphididae) were determined over a range of constant temperatures from 10 to 30 °C. The lower development threshold and the sum of effective temperatures were 6.9 °C and 90.1 °C, respectively, for preimaginal development, and 5.8 °C and 113.6 °C from birth to the onset of reproduction. Mean total fecundity ranged from 36 larvae per female at 10 °C to 76 larvae at 30 °C. On a time scale of days, net reproductive rate (R o) increased with increasing temperature while generation time (T) decreased causing the intrinsic rate of increase (rm) to increase linearly from 0.115 to 0.465. On a day‐degree scale r m only varied from 0.019 to 0.028 because the growth of R o was compensated by an increase in T with increase in temperature. The nearly constant r m in terms of day‐degrees, over a wide range of temperatures, greatly simplifies the prediction of future population numbers of A. gossypii.
Field evaluation of insect resistance in a wild tomato and its effects on insect parasitoids
Authors: Kennedy G. G. , Farrar R. R. , Barbour J. D. , Kennedy G. G.
Published: April 2011

Populations of Helicoverpa (= Heliothis) zea (Boddie), Heliothis virescens (F.), Manduca sexta (L.) and M. quinquemaculata (Haw.) and their egg and larval parasitoids were sampled in field plots of the: insect‐resistant wild tomato, Lycopersicon hirsutum f. glabratum C. H. Mull, accession PI 134417; susceptible commercial tomato cultivar ‘Better Boy’ F1 hybrid; and selected, moderately resistant backcross genotype. Densities of H. zea and H. virescens eggs and small larvae were higher on resistant genotypes than on susceptible genotypes, but densities of large larvae were similar on all genotypes. Densities of Manduca spp. larvae were too low to permit similar analyses of the effects of plant genotype. Rates of egg parasitism by Trichogramma spp. and Telenomus sphingis (Ashmead) were reduced on insect‐resistant genotypes. Rates of parasitism by the larval parasitoids Campoletis sonorensis (Cameron) and Cotesia congregata (Say) were reduced on resistant genotypes. No consistent effects on parasitism rates by Cotesia marginiventris (Cresson) were observed and parasitism rates by Cardiochiles nigriceps Viereck were unaffected.
Sub‐lethal effects of deltamethrin residues on the within‐crop behaviour and distribution of Coccinella septempunctata
Authors: Wiles John A. , Jepson Paul C.
Published: April 2011

The behaviour and distribution of adult Coccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns of C. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin to C. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub‐lethal uptake of insecticides.
Simultaneous effects of potassium, rutin and temperature on performance of Manduca sexta caterpillars
Authors: Stamp N. E.
Published: April 2011

The simultaneous effects on an insect herbivore (third instar tobacco hornworm Manduca sexta (L.): Sphingidae) of temperature (daytime temperatures of 20 °C, 25 °C and 30 °C), a mineral that may play a role in plant defense (potassium) and a common allelochemical (rutin) were examined in a factorial experiment. To manipulate potassium levels, a modified diet with limited plant material was used as the base and KCl and rutin added. Temperature affected efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), time to head‐capsule slippage, stadium duration, relative consumption rate (RCR) and relative growth rate (RGR) but not food consumed, biomass gained and approximate digestibility (AD). Potassium concentration influenced all of the variables except AD, time to head‐capsule slippage (HCS), duration of the stadium and percent of stadium time to HCS. Rutin impacted negatively on all of the variables except food consumed. Compared to larvae on the non‐rutin diets, fewer larvae fed rutin survived through molt initiation to ecdysis and fewer successfully completed ecdysis. Temperature and rutin had interactive effects for AD, ECD, RCR, RGR, time to HCS, and percent of stadium required to reach HCS. Rutin and potassium had interactive effects for biomass gained, RCR, ECI, time to HCS, duration of stadium, and percent of stadium required to reach HCS. Comparison of larval responses on an average potassium concentration (3.1%) versus high concentration (6.1%) showed that at the low daytime temperature increasing potassium concentration depressed biomass gained, but at the warmer temperatures potassium concentration had little effect unless rutin was present. In addition, potassium concentration had little impact on ECI unless rutin was present. These results indicate that significant interactive effects occur among temperature, potassium and rutin, and thus suggest that such interactive effects on larval performance may be common under field conditions, which are characterized by varying temperature and different concentrations of minerals and allelochemicals in hostplants.
Comparative headspace analysis of cabbage plants damaged by two species of Pieris caterpillars: consequences for in‐flight host location by Cotesia parasitoids
Authors: Blaakmeer A. , Geervliet J. B. F. , van Loon J. J. A. , Posthumus M. A. , van Beek T. A. , de Groot Ae.
Published: April 2011

Headspace composition, collected from intact cabbage plants and cabbage plants infested with either Pieris brassicae L. or P. rapae L. (Lepidoptera: Pieridae) first instar larvae, was determined by GC‐MS. Twenty‐one volatiles were identified in the headspace of intact plants. Twenty‐two volatiles were identified in the headspace of plants infested by P. brassicae larvae, 2 of which, Z‐3‐hexenyl butyrate and Z‐3‐hexenyl isovalerate, were not detected in the headspace of either intact or P. rapae damaged plants. In the headspace of the latter, 21 compounds were identified, all of which were also produced by intact plants. No significant quantitative differences were found between headspace composition of the plants damaged by one or the other caterpillar species. Major differences between intact and caterpillar‐damaged plants in contribution to the headspace profile were revealed for hexyl acetate, Z‐3‐hexenyl acetate, myrcene, sabinene and 1, 8‐cineole. The larval endoparasitoid Cotesia glomerata L. was attracted by the volatiles emanating from B. oleracea damaged by P. brassicae first instar larvae. C. rubecula L., a specialized larval endoparasitoids of P. rapae, was attracted by the volatiles released from the B. oleracea ‐ P. rapae plant‐host complex. This shows that cabbage plants kept under the conditions of headspace collection produce attractive volatiles for both parasitoids.
Adult response of the almond seed wasp, Eurytoma amygdali, to chemicals from its host and certain nonhosts
Authors: Kouloussis N. A. , Katsoyannos B. I.
Published: April 2011

Females of the almond seed wasp, Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), responded in an olfactometer positively to odours from almond flowers and unripe fruits, but not to almond leaf odours and odours from flowers and unripe fruits of certain other nonhost Prunus species. Males responded to none of these odours. Extracts of undamaged unripe almond fruits (using ethanol, methanol, acetone, hexane, dichloromethane, or petroleum ether) stimulated female aggregation on glass surfaces treated with these extracts; in addition, certain fruit extracts (ethanol, methanol, or acetone) stimulated oviposition. Extracts of undamaged almond leaves (ethanol, methanol, or acetone) and flowers (ethanol or methanol) also stimulated female aggregation and oviposition. Aggregation and oviposition in response to an ethanol extract of almond fruits was intense in females aged 5 to 14 days and from 12:00 to 18:00 h (photophase between 06:00 and 20:00). Certain almond fruit (ethanol, methanol, acetone or hexane) and flower extracts (ethanol or methanol) also provoked female response in the olfactometer. The results strongly suggest that certain chemical stimuli emanating from parts of the almond tree play a major role in host selection and oviposition. Some of the extracts tested may be a good source for the isolation, identification and synthesis of compounds stimulating attraction, aggregation and oviposition in nature.
Volatiles from damaged plants as major cues in long‐range host‐searching by the specialist parasitoid Cotesia rubecula
Authors: Geervliet Jacqueline B. F. , Vet Louise E. M. , Dicke Marcel
Published: April 2011

The role of volatile stimuli in the long‐range host‐searching behaviour of the specialist parasitoid Cotesia rubecula Marshall (Hymenoptera: Braconidae) was studied. Components from the plant‐host‐complex Brussels sprouts (Brassica oleracea L. var. gemmifera (DC.) Schulz. cv. ‘Titurel’)‐Pieris rapae L. (Lepidoptera: Pieridae) were compared for their attractiveness in dual choice tests in a windtunnel. Stimuli from cabbage plants that were mechanically damaged or damaged by P. rapae caterpillars were more attractive to this parasitoid species than stimuli emitted by the host larvae or their faeces. Parasitoids preferred leaves from the plant‐host‐complex over artificially damaged leaves. Undamaged cabbage plants were the least attractive to the foraging females. These results indicate that in‐flight searching behaviour of C. rubecula is guided by plant‐derived information and that for this specialist species more reliable and specific host‐derived cues play a minor role at longer distances.
Trapping and sex pheromone‐mediated flight and landing behaviour of male Ctenopseustis obliquana
Authors: Foster S. P. , Ayers R. H. , Muggleston S. J.
Published: April 2011

A sex pheromone‐baited delta trap was found to be inefficient at eliciting landing and entering of the trap by male Ctenopseustis obliquana. The inefficiency of the delta trap related to turbulence altering the pheromone plume and the concomitant effect on the flight manoeuvres of male moths. In the wind tunnel, high proportions of males flew upwind and landed on the sides, outside, of the trap, but only a relatively small proportion of these males entered the trap and contacted the sticky surface. When males approached the delta trap, they tended to fly in wide zigzags (i.e., large inter‐track reversal distances) and at an altitude near the top of the trap, where the trap was relatively narrow in width (compared to the bottom). Thus, these flight manoeuvres largely precluded males from entering the trap. Greater numbers of male moths entered the trap when: (i) the front barriers of the delta trap were removed, (ii) pheromone dosage was increased to 300μg, and (iii) the trap design was changed to a rectangular one. The first two changes appeared to influence the flight manoeuvres of males (who appeared to fly with narrower inter‐track reversal distances), while the third change apparently did not affect the flight manoeuvres of males, but rather allowed more males to enter the trap because of the greater area of the entrance. The low trap catches of male C. obliquana in the field are also a consequence of the glue which is currently used. After contact with this glue most males are able to escape, flying off the sticky surface and losing contact with the pheromone. A field trial found that delta traps with another glue caught more than three times the number of males of the related tortricid moth, Epiphyas postvittana, than delta traps with the currently used glue.
Variation in diapause and sex ratio in the parasitoid Asobara tabida
Authors: Kraaijeveld Alex R. , van Alphen Jacques J. M.
Published: April 2011

Asobara tabida Nees (Hymenoptera: Braconidae) is a widespread parasitoid, attacking larvae of Drosophila (Diptera: Drosophilidae) species in fermenting substrates. In this species, geographic variation is found in the percentage of parasitoids entering diapause and in the sex ratio of emerging parasitoids. Percentage diapause appears to be influenced by host species (more parasitoids enter diapause in D. melanogaster Meigen than in D. subobscura Collin) and temperature. It is not correlated with any of the abiotic factors investigated, but is correlated with survival probability in D. melanogaster larvae and with the time of year in which the experiment was conducted (even though none of the parasitoids experienced natural day light). Sex ratio was only found to correlate with percentage diapause, suggesting that males enter diapause more frequently than females. It is concluded that A. tabida uses diapause to survive both unfavourable abiotic and biotic circumstances.
Non‐freeze survival of spruce budworm larvae, Choristoneura fumiferana, at sub‐zero temperatures during diapause
Authors: Han Er‐Ning , Bauce Eric
Published: April 2011

Spruce budworm larvae, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), in early‐, mid‐ and late‐diapause (maintained at 2 °C), were exposed to various sub‐zero temperatures, above the supercooling point, for different periods to determine the insect's cold‐hardiness in terms of non‐freeze survival. Larvae which were in the middle of diapause showed the highest survival (percentage of larvae emerging from hibernacula after diapause), followed by larvae in late‐ and early‐diapause respectively. When exposed to −23 °C, larvae which were acclimatized to outside air temperatures had a much higher survival than the larvae maintained at 2 °C. This survival was correlated with a glycerol content that was ten times higher and a depressed supercooling point in acclimatized larvae compared to lab‐maintained larvae. Experiments also demonstrated that mortality of the larvae maintained in an extended supercooled state at −23 °C was due to cold injury rather than freezing. The present study supports the hypothesis that glycerol may have a cryoprotective role other than depressing the supercooling point in freeze‐intolerant insects and highlights the importance of investigating non‐freeze mortality during insect diapause.

Des larves de tordeuse des bourgeons de l'épinette, Choristoneura fumiferana (Clem.), en début, milieu et fin de diapause (maintenue à 2 °C) furent soumises à divers régimes de températures supérieures au point de congélation cellulaire, de façon à déterminer la capacité de l'insecte à survivre à ces températures. Les larves en milieu de diapause furent celles ayant le mieux survécu (proportion des larves émergeant de leur hibernacula après la diapause). Elles furent suivies respectivement par celles en fin et en début de diapause. La suivie larvaire, suite à une exposition à −23 °C, fut plus élevée dans le cas des larves préalablement acclimatées aux températures de terrain que dans le cas des larves maintenues à 2 °C. Comparativement aux larves non acclimatées sur le terrain, le point de congélation cellulaire des larves acclimatées était inférieur et leur contenu en glycérol était dix fois plus élevé. Cette étude a aussi montré que la mortalité des larves maintenues durant une longue période à −23 °C ne fut pas causée par un phénomène de congélation cellulaire mais plutôt par d'autres effets létaux du froid. Les résultats de cette étude sont en accord avec l'hypothèse selon laquelle le glycérol jouerait, en tant que cryoprotectant, un rôle autre que celui d'abaisser les points de congélation cellulaire des insectes du type intolérant au gel. De plus, ces résultats montrent l'importance détudier la mortalité induite par les températures situées au‐dessus du point de congélation cellulaire durant la diapause de l'insecte.
Design and use of a simulation model to evaluate germplasm for antibiotic resistance to the greenhouse whitefly (Trialeurodes vaporariorum) and the sweetpotato whitefly (Bemisia tabaci)
Authors: Van Giessen W. A. , Mollema C. , Elsey K. D.
Published: April 2011

SARAH (Software for the Assessment of antibiotic Resistance to Aleyrodidae in Host plants) is a deterministic simulation model of whitefly population growth based on whitefly life‐history components determined on individual plants. The life‐history components recorded were oviposition rate, adult survival, pre‐adult survival, developmental period, and sex ratio. The simulation model serves as a tool to combine these components and to obtain a single criterion for (antibiotic) resistance. The criterion used was the decrease in simulated intrinsic population growth rate, rs, relative the rs value determined on a susceptible control genotype. This model‐based evaluation method was tested using the greenhouse whitefly, Trialeurodes vaporariorum Westwood, on tomato and the sweetpotato whitefly, Bemisia tabaci Gennadius, on tomato, eggplant, collard, and pepper.

To study its consistency over time, the evaluation method was repeated six times for T. vaporariorum on a susceptible and a resistant tomato cultivar. Simulated intrinsic population growth rate was more consistent in indicating resistance than any of the individual life‐history components. Of ten L. hirsutum accessions tested for resistance to T. vaporariorum, three exhibited rs values that were significantly lower than those for the susceptible control. In addition, on these ten L. hirsutum accessions, a significant positive correlation was observed between rs and sex ratio (# females/# males).

Four host plant species (tomato, collard, eggplant, and pepper) were evaluated for resistance to B. tabaci. All life‐history components and rs values varied among host species, while a negative rs value was observed for B. tabaci on pepper.

A high correlation was found between results from a sensitivity analysis of SARAH and results from a sensitivity analysis of a validated whitefly population simulation model by Yano et al. (1989a). Significant correlations were found for the relationships between oviposition rate, adult survival, or pre‐adult survival and rs, indicating that none of these life‐history components can be omitted from the test procedure. This model‐based evaluation method offers a standardized way to quantify levels of antibiotic resistance to whiteflies and will enhance efficiency in breeding programs.
Mechanical and salivary aspects of potato leafhopper probing in alfalfa stems
Authors: Ecale Carol L. , Backus Elaine A.
Published: April 2011

Studies were conducted to separate the salivary and mechanical aspects of probing damage by the potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), to stem vascular tissue of alfalfa, Medicago sativa L. Implantation of salivary gland tissue or fed‐upon artificial diet under the stem epidermis yielded no evidence, three days later, of hopperburn‐associated, anatomical changes. Mechanical puncturing of stems with implements approximating the size and shape of leafhopper stylets caused some anatomical changes, three days later, similar to those underlying hopperburn, i.e. tracks of necrosis, chlorosis, cell enlargement, and cell division. These changes, however, were much less severe than those observed in tissues three days after potato leafhopper probing. In contrast, puncturing through salivary gland or Malpighian tubule tissues produced extreme hyperplasia and other symptoms of wounding in cells near the puncture. This was similar to but more severe than effects from leafhopper probing, and was probably caused by leafhopper structural tissues or larger amounts of saliva being conveyed into the plant than normally occurs during leafhopper probing. We conclude that both salivation and mechanical wounding by leafhopper stylets are probably necessary to cause hopperburn‐associated anatomical changes to vascular tissue in stems of alfalfa. This conclusion supports our hypothesis that hopperburn is a saliva‐enhanced wound response.
Life history and life table parameters of the predatory mite Typhlodromus talbii
Authors: Camporese Paolo , Duso Carlo
Published: April 2011

The predatory mite Typhlodromus talbii Athias‐Henriot occurs in European vineyards and is often associated with economically important species. Neither its role in vineyards nor the factors affecting its population dynamics and relationships with other phytoseiid species are well known. The development and the reproduction of T. talbii were studied in the laboratory by rearing the predator on different kinds of food (Panonychus ulmi, Eotetranychus carpini, Colomerus vitis, Tydeus caudatus, Mesembryanthemum criniflorum pollen). Overwintered females reared on tydeids survived for long periods and laid eggs, but they died after a few days when spider mites or pollen were provided. Development occurred on all mite species but not on pollen. Developmental times on tydeids were shorter than on the other prey. Oviposition was recorded on tydeids and, to a lesser extent, on eriophyids but not on spider mites or pollen. Experiments on tydeids, which resulted as being the best food, were conducted at two temperatures (20° and 27°C). The highest temperature affected the duration of development and oviposition rates positively, but total fecundity was similar. Predators reared at 27°C consumed more prey than those reared at 20°C. The life table parameters of the species were evaluated on T. caudatus (at 20° and 27°C) and on C. vitis. The highest rm of T. talbii was found for individuals reared on T. caudatus at 27°C (0.165). Lower values were obtained on the same prey at 20°C (0.089) or on C. vitis (0.030). The feeding habits of T. talbii may explain why the species coexists with the generalist Amblyseius aberrans or Typhlodromus pyri.
Decrease in tolerance to fenvalerate, in resistant Helicoverpa armigera after pupal diapause
Authors: Daly J. C. , Fisk J. H.
Published: April 2011

Pyrethroid resistant and susceptible adults of Helicoverpa armigera (Lepidoptera: Noctuidae) were screened for tolerance to pyrethroids after 6 wk or 12 wk pupal diapuse. Resistant larvae and F2 larvae from a cross between resistant and susceptible parents (two replicates), were reared under conditions to induce pupal diapause. After eclosion, adults were tested in glass vials coated with the pyrethroid fenvalerate, at a dose (DD) that is known to discriminate between susceptible and heterozygous resistant individuals. In all diapause experiments, the frequency of resistance was lower in the test groups that had experienced diapause compared with the non‐diapausing control group. The underlying cause of the decline is not certain but selective mortality of resistant versus susceptible individuals could not account for all the difference in two of the three experiments ‐ tolerance to the pyrethroid, fenvalerate, is most likely to have declined either as a consequence of diapause or from the extended time of development associated with diapause. These results indicate that monitoring programs could underestimate pyrethroid resistance frequencies when using H. armigera adults emerging from diapause.
Factors affecting entomopathogenic nematode infection of Plutella xylostella on a leaf surface
Authors: Baur M. E. , Kaya H. K. , Thurston G. S.
Published: April 2011

We investigated the ability of entomopathogenic nematodes to infect diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae) on a leaf surface. In a leaf disk assay, mortality of late stage DBM larvae ranged from <7% caused by Steinernema kushidai Mamiya to >95% caused by S. carpocapsae (Weiser) All strain. LC50 values for S. carpocapsae, S. riobravis Cabanillas, Poinar & Raulston, and Heterorhabditis bacteriophora Poinar NC1 strain were 14.6, 15.4, and 65.4 nematodes/larva, respectively. S. carpocapsae, S. riobravis, and H. bacteriophora caused 29%, 33%, and 14% mortality of DBM pupae, respectively. DBM mortality caused by S. carpocapsae on radish declined at low (<76%) to moderate (76–90%) RH, because nematode survival and infectivity declined at low (76%) to moderate (76–90%) RH. However, DBM mortality caused by S. riobravis did not decline with RH. S. riobravis survival declined with RH, but infectivity did not. Overall, nematode survival and infectivity to DBM larvae were lower for S. riobravis than for S. carpocapsae. In addition, DBM mortality was higher on radish plants (pubescent leaves) than on cabbage plants (glaborous leaves).
Antibiosis and antixenosis of chrysanthemum cultivars to the aphid Aphis gossypii
Authors: Storer J. R. , van Emden H. F.
Published: April 2011

An assessment was made of the antibiotic and antixenotic resistance of three cultivars of autumn flowering chrysanthemum (derived from Dendranthema morifolium (Ramat) Tzvelev and D. indicum (L.) Desmoulins) to the aphid Aphis gossypii Glover. Antibiosis was also assessed at the top, middle and lower leaves of the plant. The three cultivars showed a range of resistance with Hero being the most susceptible, Surfine the most resistant and Purple Anne intermediate. There was a trend for antibiosis to improve with position down the plant, however there were cultivar by position interactions. Antixenosis was assessed at two levels, the first being under conditions where the aphid had complete access to the plant in caged choice assays and the second being under conditions where the aphid only had host odour to assess under olfactometer choice conditions. Preferences under the caged choice conditions found Hero to be the most preferred cultivar while there was no preference shown between Purple Anne and Surfine. However, olfactometer assessments showed Hero to be the least preferred of the three cultivars and, again, no preferences could be found between Purple Anne and Surfine.
The effects of different components of an artificial food on adult green lacewing (Chrysoperla carnea) fecundity and longevity
Authors: McEwen P. K. , Kidd N. A. C.
Published: April 2011

Artificial foods comprising yeast products, sugar and water are often sprayed in the field to increase numbers of naturally occurring lacewing populations. The relative importance of the components of these foods for green lacewing (Chrysoperla carnea Stephens) fecundity and longevity is investigated in this paper. In laboratory experiments insects receiving only sugar solution lived significantly longer than those receiving diets containing both sugar and yeast (P<0.05). The inclusion of yeast is required for egg production, but few eggs are produced on yeast solution alone. For maximum egg production, food containing yeast and sugar must be offered on more than one occasion. Compared with insects given a diet comprising yeast autolysate, sugar, and water in the ratios 4:7:10, small but significant reductions in egg production rate were noted when the amount of either the yeast, or both the yeast and the sugar, was halved. The implication of these findings for the field is that viscous foods must be offered on a regular basis for maximum effectivity.