bluuebunny/crossref_metadata_2025 huggingface dataset:
Herbivore‐induced emissions of maize volatiles repel the corn leaf aphid, Rhopalosiphum maidis
Authors: Bernasconi Marco L. , Turlings Ted C. J. , Ambrosetti Lara , Bassetti Paolo , Dorn Silvia
Published: October 2003

When maize plants, Zea mays L., are mechanically damaged and the damaged sites are treated with caterpillar regurgitant, the plants will release a specific blend of volatiles. It is known that these volatiles can be attractive to natural enemies of herbivores. We hypothesise that the plant volatiles constitute part of the induced plant defence and that herbivores will be affected by the odours as well. In laboratory and semi‐field studies this hypothesis was tested for the aphid Rhopalosiphum maidis (Fitch) (Rhynchota, Sternorrhyncha, Aphididae).

In a Y‐tube olfactometer significantly more aphids chose the odour of healthy, undamaged maize seedlings when tested against clean air or plants treated with regurgitant. Clean air was chosen more often when tested next to the odour of treated plants. This apparently repellent effect of the odour of treated plants was significant for winged aphids, but not for the wingless aphids.

In field experiments aphids were released in the centre of circles of eight potted maize plants. Four plants in each circle were damaged and treated with caterpillar regurgitant while the other plants were left unharmed. At different intervals after aphid release, the number of aphids was counted on each plant. Significantly fewer winged and wingless aphids were found back on treated plants than on healthy plants.

We suggest that herbivores may be repelled by the odours because they could indicate that: 1) the plant has initiated the production of toxic compounds; 2) potential competitors are present on the plant; 3) the plant is attractive to parasitoids and predators. Aphids may be particularly sensitive to induced maize volatiles because one of the major compounds emitted by the plant is (E)‐β‐farnesene, which is a common alarm pheromone for aphids. Collections and analyses of the odours emitted by crushed R. maidis confirmed that it too emits (E)‐β‐farnesene when stressed. The results are discussed in context of plant defence strategies and their possible exploitation for the control of pest insects.
Development, survival and fecundity of the urine fly, Scatella (Teichomyza) fusca and predation by the black dumpfly, Hydrotaea aenescens
Authors: Vibe‐Petersen Solveig
Published: October 2003

Development, survival and fecundity for Scatella (Teichomyza) fusca Maquart (Diptera: Ephydridae) were studied at 20 ± 1 °C and 85 ± 10% r.h. Mean (± S.E.) developmental times of eggs, larvae and pupae were 4.0 ± 0.06, 14.9 ± 0.19 and 14.6 ± 0.11 days, respectively, the mean (± S.E.) survival of the original egg cohort to the start of larval, pupal and adult stage being 77.2 ± 3.2%, 54.5 ± 2.6% and 47.9 ± 3.5%, respectively. Females and males displayed approximately straight survivorship curves during adult life, implying constant mortality rates. Mean (± S.E.) adult longevity was 41.6 ± 2.98 days for females and 51.2 ± 3.91 days for males. Assuming a stable age distribution the population consisted of 56% eggs, 31% larvae, 6% pupae and 7% adults. Oviposition peaked when females were 25 days old, and the highest reproductive values (RVx) (mean ± S.E.) ranged from 129.1 ± 7.57 to 138.5 ± 6.83 for individuals 17–27 days old. A female deposited a mean (± S.E.) of 614.7 ± 35.9 female eggs over a maximum life span of 93 days. The basic reproductive rate (R0) (mean ± S.E.) was 173.0 ± 14.2 female offspring per female and the intrinsic rate of natural increase of female individuals (r) (mean ± S.E.) was 0.088 ± 0.001 day−1. The mean (± S.E.) generation time (T) was 57.8 ± 0.78 days. In cultures with equal numbers of first instar S. fusca larvae and predacious third instar larvae of Hydrotaea aenescens (synonymous Ophyra aenescens) Wiedemann, mean (± S.E.) survival to the adult stage of S. fusca (16.7 ± 8.8%) was significantly lower than in controls with S. fusca alone (58.3 ± 7.4%). The potential significance of predation by H. aenescens on S. fusca in pig farms is discussed.
Genetic differentiation of groundnut seed‐beetle populations in Senegal
Authors: Sembène Mbacké , Delobel Alex
Published: October 2003

Caryedon serratus, the groundnut seed‐beetle, is a major pest of groundnut (Arachis hypogaea), an introduced legume in the subfamily Papilionoideae. Native hosts of C. serratus in Senegal include Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica, all of which belong to the legume subfamily Caesalpinioideae.

The biology and natural history of C. serratus suggest that it is a candidate for population differentiation via host‐race formation. Evidence for host‐tree associated differentiation in C. serratus would be important for the design of rational pest management practices.

To test this possibility, we analyzed the genetic structure of 20 adult collections of C. serratus from six sites in Western Senegal, on its five hosts. Results show a strong differentiation of insects from different host trees, with specimens from C. sieberiana possibly representing a sibling species and insects from B. rufescens a distinct host‐race.
Combined effects of allelochemicals, prey availability, and supplemental plant material on growth of a generalist insect predator
Authors: Weiser L. A , Stamp N. E.
Published: October 2003

We examined the effects of the presence of plant allelochemicals in prey diet, prey availability and supplemental plant material on the growth of the generalist predator Podisus maculiventris (Hemiptera: Pentatomidae). We tested two different nymphal stages of this predator. Third to fourth instar nymphs and fifth instar nymphs were fed a diet of prey (Manduca sexta larvae, Lepidoptera: Sphingidae) without allelochemicals in their diet or prey fed maximal levels of allelochemicals (tomatine, rutin and chlorogenic acid) found in their host plant (Lycopersicon esculentum). The nymphs were fed prey ad libitum, once every three days, or once every five days. They were given either no supplemental plant material or a 2 cm slice of green bean pod (Phaseolus vulgaris). We also conducted another experiment with fifth instar nymphs using the same conditions, except that mean levels of allelochemicals found in the host plant were fed to prey instead of maximal levels and the prey were provided either once a day or once every five days. For all experiments, prey scarcity depressed developmental rate, weight gain and relative growth rate. Overall, there was no negative effect of allelochemicals in the diet of the prey on these variables when predators were supplied with an excess of prey, but allelochemicals in the prey diet negatively affected these predators when prey were scarce. The addition of plant material to the diet of third to fourth instar nymphs did not have any effect on developmental rate, final dry weight, or relative growth rate. However, for fifth instar nymphs, the addition of plant material negatively affected these variables. Thus, the addition of plant material to the diet of the nymphs did not alleviate the negative effects of prey scarcity or allelochemicals in prey diet.
The effect of parasitism by Aphelinus abdominalis and drought on the walking movement of aphids
Authors: Honěk Alois , Jarošik Vojtěch , Lapchin Laurent , Rabasse Jean‐Michel
Published: October 2003

The effect of simulated plant stress and parasitism by Aphelinus abdominalis (Dalman) on the mobility of four species of aphids was investigated. The aphids were placed on water stressed potted plants or on excised leaf segments on dry or moist filter‐paper in Petri dishes. Winter wheat (Triticum aestivum) was infested with Metopolophium dirhodum (Walker), Sitobion avenae (F.) and Rhopalosiphum padi (L.) (segments only), aubergine (Solanum melongena) leaf segments with Macrosiphum euphorbiae (Thomas). The aphids that moved off the plants were removed and their development stage determined at 24‐h (drought‐stressed plants) or 3‐h (leaf segments) intervals. On intact plants, aphid larvae were reluctant to move, and only moved after moulting into adults. On cut leaves, young 1st and 2nd instar larvae were more reluctant to move than 3rd and 4th instar larvae and adults. The numbers moving were initially positively correlated with aphid population density, and in M. euphorbiae occurred mainly during the night. Depending on aphid species and parasitoid age, parasitism by A. abdominalis retarded or accelerated movement, but the differences between young and old larvae and adults persisted after parasitism. A. abdominalis lays male eggs in small hosts and female eggs in large hosts. Consequently, its sex ratio was affected by differential movement of the host aphids of the male and female parasitoids. Old larvae and adult aphids readily moved and carried off female parasitoids, while the small aphids were more likely to remain and give rise to male‐biased sex ratios.
Restricted host range of the weevil Aubeonymus mariaefranciscae, a new sugar‐beet pest
Authors: Marco V. , López‐Olguín J.F. , Ortego F. , Castañera P.
Published: October 2003

The extent of feeding, fecundity and fertility of a new sugar beet pest, Aubeonymus mariaefranciscae Roudier (Coleoptera: Curculionidae), on a range of plants from different families was determined. We have found that the adult weevils were only able to feed and oviposit on two closely related cultivated plants, beet and sugar beet, both subspecies of Beta vulgaris L., suggesting a restricted host range for this curculionid. None of 16 secondary metabolites (widely distributed among plants, and representative of different chemical groups), nor any of 19 non‐host extracts from 13 different families, deterred the adults of this curculionid from feeding on sugar beet. We found a phagostimulatory effect when beet and sugar beet homogenates from various plant tissues were supplied to adult weevils on weeds that they do not feed on. Conversely, no effect was observed when sucrose was provided. These findings suggest that host selection by A. mariaefranciscae adults is due to the presence of an undetermined phagostimulant compound(s) in beet and sugar beet, instead of the recognition of deterrent substances among the non‐host plants.
A portable electroantennogram sensor for routine measurements of pheromone concentrations in greenhouses
Authors: van der Pers J. N. C. , Minks A. K.
Published: October 2003

Mating disruption using pheromone dispensers is an emerging insect control method in greenhouses in the Netherlands. For routine measurements of the pheromone level in greenhouses a portable and compact device based on electroantennography (EAG) was developed. The instrument was tested in different greenhouses under varying conditions using antennae of males of the noctuid moth Chrysodeixis chalcites. Relative differences in pheromone concentration between greenhouses loaded with pheromone dispensers and control greenhouses could be measured in a reliable way. Changes in pheromone concentration were clearly demonstrated by measurements during the growing season. The advantages of the instrument presented over previously described devices are its true portableness, ease of use and uncomplicated measuring principle. The device can be operated routinely by non‐experts, and many measurements can be made in a short period of time. Preliminary outdoor measurements using antennae of male Cydia pomonella as sensor showed the potential of the instrument for use in the open field. The portable EAG sensor described here may provide a practical means for monitoring pheromone concentration and dispersal from dispensers applied for mating disruption.
Prey finding by larvae and adult females of Episyrphus balteatus
Authors: Bargen Holger , Saudhof Kathrin , Poehling Hans‐Michael
Published: October 2003

The prey‐location behaviour of larvae of Episyrphus balteatus DeG. (Dipt.: Syrphidae) was investigated in two different experimental set‐ups. First instar larvae exhibited directed search over short distances, guided by olfactory cues from aphids, but not from honeydew. However, second and third instars did not respond to aphid‐plant‐complex odours in a 4‐arm‐olfactometer. Aphid extracts, honeydew and sucrose were found to be feeding stimulants for the larvae. The oviposition behaviour of female syrphids was investigated in a series of two‐choice experiments: females were able to evaluate aphid numbers and adjust oviposition rates accordingly, with higher prey numbers eliciting increased oviposition, even when the aphids were removed at the start of the experiment. The presence of conspecific syrphid larvae did not inhibit oviposition when the females were deprived of suitable oviposition sides before the experiments were conducted.
Patterns of mating between two closely related ground crickets are not influenced by sympatry
Authors: Gregory Pamela G. , Remmenga Marta D. , Howard Daniel J.
Published: October 2003

Allonemobius fasciatus (De Geer) and A. socius (Scudder) (Orthoptera: Gryllidae) are small ground‐dwelling crickets that meet and hybridize, to a limited extent, in a mosaic contact zone stretching from New Jersey to at least as far west as Illinois. To determine whether short‐range signals such as visual cues, tactile stimulation, or pheromones are important in limiting gene flow between A. fasciatus and A. socius we carried out a study in the laboratory. A male or a female was placed in a cage with an A. fasciatus and A. socius individual of the opposite sex and the outcome, a conspecific or a heterospecific mating, was recorded. Overall, conspecific matings occurred more frequently than heterospecific matings. However, individuals from areas of sympatry were no more likely to mate with a conspecific than were individuals from areas of allopatry. Thus, the challenge posed by a related species has not resulted in a strengthening of positive assortative mating in these crickets.
Physical and chemical plant characters inhibiting the searching behaviour of Trichogramma chilonis
Authors: Romeis J. , Shanower T.G. , Zebitz C.P.W.
Published: October 2003

Several plant characters are known to affect the searching behaviour and parasitization efficiency of Trichogramma spp. (Hymenoptera: Trichogrammatidae). In this study, plant characters contributing to the low Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) egg parasitism levels on pigeonpea (Cajanus cajan (L.) Millspaugh) were investigated. The efficiency of T. chilonis on pigeonpea was dependent on the plant structure on which the host eggs were found. In a cage experiment, more than 55% of eggs placed on leaves were parasitized, while 1% of eggs on calyxes and no eggs on pods were parasitized. In a filter paper bioassay, parasitoids were deterred by acetone and hexane surface extracts from pigeonpea pods but showed no response to water extract. The searching behaviour of the parasitoids was not affected by different solvent extracts from the surface of pigeonpea leaves. In a four‐armed airflow olfactometer, T. chilonis was repelled by volatiles from pigeonpea pods but showed no response to volatiles derived from hexane extract of pod surfaces. Volatile infochemicals and hexane surface extracts from pods of two wild Cajanus species, C. scarabaeoides (L.) Thours and C. platycarpus (Bentham) van der Maesen, were similarly deterrent to T. chilonis. The movement of the parasitoids on pigeonpea pods and calyxes was inhibited by long trichomes and wasps were trapped by sticky trichome exudates. Parasitoids walked significantly faster on leaves than on pods. The walking speed on both pods and leaves increased significantly after washing with hexane. The results presented in this paper show that the plant growth stage and the plant structures preferred by H. armigera for oviposition are the least suitable for T. chilonis, contributing to the low parasitoid efficiency on pigeonpea.
Fecundity and juvenile survival of Bembidion lampros and Tachyporus hypnorum
Authors: Petersen Mette K.
Published: October 2003

Fecundity and development from first instar larvae to adult beetles were studied for Bembidion lampros Herbst (Coleoptera; Carabidae) and Tachyporus hypnorum F. (Coleoptera; Staphylinidae). Both species reproduce in arable fields, where they are known to contribute to the natural control of cereal aphids. They are univoltine and have similar life cycles and development times. T. hypnorum females laid approximately 3 times more eggs than B. lampros females. Relative lifetime fecundity of B. lampros was very low with an average of 10 eggs per female. Based on the time where half of the populations had dispersed from the overwintering sites into an arable field B. lampros started egg‐lay 100°D (°C>9) and T. hypnorum 200°D (°C>3) after dispersal. Mortality in the juvenile stages was found to be an important factor in the population dynamics of both B. lampros and T. hypnorum. The survival from first instar larvae to adults was on average 34% for B. lampros independent of soil type, 21% for T. hypnorum developed in sandy soil and 49% when developed in clayey soil under semi‐field conditions. Enlargement of B. lampros and T. hypnorum populations to increase the natural control of aphids during their establishment in cereal fields may be possible if the conditions for juvenile development are improved.
Potential application of the entomopathogenic fungus, Nomuraea rileyi, for control of the corn earworm, Helicoverpa armigera
Authors: Tang Li‐chang , Hou Roger F.
Published: October 2003

The entomopathogenic fungus, Nomuraea rileyi, caused 90.5–100% mortality in fourth‐instar larvae of the corn earworm, Helicoverpa armigera, when applied at 107 conidia/ml to corn silks, and leaves of soybean, tomato and chrysanthemum. The LT50 was 5.9–6.7 days. The fifth‐instar larvae showed a mortality of 94.6% on soil with 20% water content, and 41.7% on 10% water content when the soil surface was sprayed with 108 conidia/ml suspension. Five fungicides, eight insecticides and nine herbicides, which are commonly used in corn fields, were evaluated for inhibition to conidial germination by a paper disk test. Among them, only two fungicides, viz., maneb and propineb, were highly inhibitory, while insecticides and herbicides examined were not inhibitory to the fungus. Field applications of N. rileyi conidial suspension to neonate larvae were found to be as effective as 40.46% carbofuran (EC) at 800‐fold dilution in controlling corn earworm based on marketable ears. It is thus suggested that N. rileyi has potential to be a microbial control agent for this insect.
Treatment of adult Coleoptera with a chitin synthesis inhibitor affects mortality and development time of their progeny
Authors: Elek Jane A.
Published: October 2003

A group of insect growth regulators, the chitin synthesis inhibitors (CSIs), are being more widely used as many insects have become resistant to broad‐spectrum insecticides. This study investigated the mode of action of one CSI, particularly looking at the delayed effect of treating adult insects on the survival and development of their progeny. The study describes the responses of adult stored grain beetles Sitophilus oryzae (L.) (Curculionidae) and Rhyzopertha dominica (F.) (Bostrichidae) to wheat treated with chlorfluazuron. For both species, wheat treated with chlorfluazuron reduced progeny survival at a constant rate from 1 day to 8 weeks after it had been treated. There was a direct, negative concentration‐time relationship between the treatment of the adults with chlorfluazuron‐treated wheat and the survival and developmental rate of their progeny. Adults that were pre‐exposed for one or more weeks before oviposition to wheat treated with chlorfluazuron had significantly lower progeny survival than adults that were not pre‐exposed. The EC95 values were 16‐fold higher for R. dominica and 40‐fold higher for S. oryzae from assays without pre‐exposure, than with pre‐exposure. Pre‐exposure of R. dominica with 0.1 mg kg−1 and of S. oryzae with 0.4 mg kg−1 of chlorfluazuron reduced progeny survival by 95%. Higher concentrations of chlorfluazuron produced a reduction in mean population developmental time of several days. These findings have important implications for bioassays of CSIs, since pre‐exposure of the adults can significantly reduce the numbers of F1 progeny. Therefore standard bioassays may seriously underestimate the efficacy of the CSI being assayed.
Instar‐dependent hemocyte changes in Pieris brassicae after parasitization by Cotesia glomerata
Authors: Bauer Evelyne , Trenczek Tina , Dorn Silvia
Published: October 2003

Cotesia glomerata L. (Hymenoptera: Braconidae) is a parasitoid of early instar larvae of Pieris brassicae L. (Lepidoptera: Pieridae). Late instars of P. brassicae can more often overcome parasitization by hemocytic encapsulation of C. glomerata eggs. Short‐term hemocyte responses to parasitization were examined in third and fourth instar larvae of P. brassicae. Total and differential hemocyte counts did not differ between parasitized and unparasitized host larvae. A rapid, but temporary decrease of total hemocyte as well as plasmatocyte numbers was observed immediately after oviposition. Numbers of hemocytes adhering to tissues were shown to be the same in untreated, wounded and parasitized P. brassicae larvae by tracing hemocytes with monoclonal antibodies as markers. The in vitro spreading ability of hemocytes from unparasitized third and fourth instar larvae was lower than that of the last instar's; parasitization, however, had no influence on hemocyte spreading. We therefore suggest that the higher parasitization success of C. glomerata in earlier instars of P. brassicae is mainly due to the low spreading ability of the hemocytes. Abbreviations: ACS – anticoagulant saline; BSA – bovine serum albumin; DABCO – 1,4‐diazabicyclo‐[2,2,2]‐octane; DHC – differential hemocyte count; FITC – fluorescein isothiocyanate; GR – granular cells; LPS – lipopolysaccharide; mAb – monoclonal antibody; OE – oenocytoids; PL – plasmatocytes; PRO – prohemocytes; PS – Pieris saline; PVP – polyvinylpyrrolidone; TBS – tris‐buffered saline; THC – total hemocyte count.
Studies of the growth, development and reproductive performance of the aphid Myzus persicae on artificial diets containing potato glycoalkaloids
Authors: Fragoyiannis D. A. , McKinlay R. G. , D'Mello J. P. F.
Published: October 2003

Peach potato aphids Myzus persicae (Sulzer) (Homoptera: Aphididae) were reared on artificial diets containing the steroidal glycoalkaloids (GAs) α‐solanine and α‐chaconine in concentrations lower or similar to those observed in potato leaves. The adults proved to be susceptible to high concentrations (80–160 mg GA /100 ml of diet) showing reduced fecundity, diet uptake and increased mortality in comparison to controls. Ingestion of these artificial diets by nymphs delayed maturity and decreased the intrinsic rate of natural increase. GAs in low concentrations marginally stimulated the reproductive performance and diet acceptability of this aphid. The possibility of GAs exerting a defensive role in potato plants against aphids is discussed.
Nematode parasitism in a Danish drosophilid community: further evaluation of the disproportionate parasitism hypothesis
Authors: Hardy Ian C. W. , Gillis Jaklien E. M.
Published: October 2003

The nematodes Parasitylenchus diplogenus and Howardula aoronymphium (Allantonematidae) are parasites of drosophilids (Diptera). Nematodes were found in 3/14 drosophilid species sampled in Danish woodlands: Drosophila phalerata Meigen (3.5% parasitism) was parasitized by H. aoronymphium and D. obscura Fallén (0.5%) and D. subobscura Collin (2.1%) by P. diplogenus. Parasitism was generally rare, and few drosophilid species parasitized, compared to elsewhere in Europe. Parasitism was positively correlated with relative host abundance both within Denmark and across communities, suggesting that species diversity is promoted by a disproportionately high parasitism of more common host species. The prevalence of H. aoronymphium, but not P. diplogenus, parasitism is positively related to temperature across communities.
Development of pheromone‐based mating disruption for control of the eye‐spotted bud moth, Spilonota ocellana
Authors: McBrien H. L. , Judd G. J. R. , Borden J. H.
Published: October 2003

The potential for pheromone‐based mating disruption of eye‐spotted bud moth (ESBM), Spilonota ocellana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), in apple orchards in the Okanagan Valley of British Columbia was examined in small‐plot trials. In a preliminary experiment, treatment of the orchard atmosphere with a 99:1 blend of Z8‐tetradecenyl acetate (Z8‐14:OAc) and Z8‐tetradecenyl alcohol (Z8‐14:OH) completely inhibited captures of male ESBM in pheromone‐baited traps, but treatment with Z8‐14:OAc alone did not. Therefore, all subsequent trials used the two‐component blend as a disruptant. Mean catches of male ESBM in traps baited with 0.1, 1, 10, or 20 mg of 99:1 Z8‐14:OAc and Z8‐14:OH were significantly reduced (81–97%) in pheromone‐treated plots relative to similar traps placed in control plots. In both control and treated plots, there was a significant positive relationship between trap bait dose and trap catch. In pheromone‐treated plots, this suggests that high doses of trap baits over‐ride the camouflage effect of disruption or overcome the effect of sensory adaptation and habituation. The number of virgin‐female baited traps capturing at least one male ESBM was reduced by 96%, and mating of virgin females on mating tables was reduced by 95% in plots treated with the two‐component pheromone. The total amount of Z8‐14:OAc released from pheromone disruption dispensers during the latter field trials was estimated to average 6.4 g ha−1 over 11 days or 26.4 mg ha−1 h−1. The low levels of Z8‐14:OH released from disruption dispensers could not be estimated by GC analysis. Dispensers loaded with a 99:1 blend of Z8‐14:OAc and Z8‐14:OH were highly attractive to males in baited traps, indicating that they have the potential to induce false trail following.
Endogenous and exogenous factors affecting parasitism of gypsy moth egg masses by Ooencyrtus kuvanae
Authors: Hofstetter Richard W. , Raffa Kenneth F.
Published: October 2003

Factors affecting the orientation, reproduction, and sex ratio of the egg parasitoid Ooencyrtus kuvanae Howard were examined. Adult females were attracted to airborne volatiles from the egg mass and accessory gland of the primary host, the gypsy moth Lymantria dispar L. Visual cues also affected host selection. Background colors against which egg masses were placed affected oviposition preference. In the absence of egg masses, color variation did not affect wasp behavior. Light is required for parasitism by O. kuvanae. The age and density of both the host and parasitoid affected wasp reproduction and sex ratios. Older egg masses issued relatively fewer wasps and higher proportions of males than did young egg masses. Likewise, wasp reproduction and the proportion of females declined with wasp age. Larger egg masses produced more wasps and lower proportions of males than did smaller egg masses. The number of offspring per female, and the proportion of female offspring, were inversely related to wasp density. Implications to biological control of the gypsy moth and parasitoid ecology are discussed.
Inter‐ and intra‐ species differences in plants as hosts to Tyria jacobaeae
Authors: Tinney G. W. , Hatcher P. E. , Ayres P. G. , Paul N. D. , Whittaker J. B.
Published: October 2003

The effect of three food plants, Senecio jacobaea L., Senecio vulgaris L. and Tussilago farfara L., and rust infection of two of them on the performance and host choice of Tyria jacobaeae L. was assessed. The nitrogen content of healthy and infected food plants was measured.

Larvae reared on S. vulgaris had a lower relative consumption index and higher efficiency of conversion of ingested food than those reared on the other two species. These differences were correlated with the higher nitrogen content of S. vulgaris compared to T. farfara and S. jacobaea. Larvae reared on T. farfara were significantly smaller at pupation than those reared on the other species. In both larval and adult choice tests between healthy plants of the three species, S. jacobaea was always the preferred host plant. Adults completely avoided T. farfara in oviposition choice tests.

Infection of S. vulgaris with Coleosporium tussilaginis (Pers) Lev. had no effect on larval performance. Infection of S. vulgaris with Puccinia lagenophorae Cooke. caused differences in larval performance. Infection of T. farfara with C. tussilaginis had a detrimental effect on larval performance: larvae were smaller, fed for longer and had lower growth rates than those reared on healthy T. farfara. Healthy T. farfara had a higher leaf nitrogen content than the infected T. farfara. In choice tests against healthy leaves, larvae avoided leaves of both S. vulgaris and T. farfara infected with C. tussilaginis. Larvae and adults showed no preference between S. vulgaris leaves infected with P. lagenophorae or healthy leaves.

In the field, factors such as plant size may be important in dictating adult and larval preference for a particular host plant species. Rust infection of some species influenced larval performance and host choice, demonstrating the importance of studying multitrophic aspects of plant – insect interactions.
Onset of a decline in the quality of sugar beet as a host for the aphid Myzus persicae
Authors: Kift N.B. , Dewar A. M. , Dixon A. F. G.
Published: October 2003

The results presented in this paper suggest that sugar beet became less suitable as a host for aphids after late June and early July, when the plants were at the 10–12 leaf stage. This was indicated by a faster rate of aphid mortality and greater incidence of dark stomach deposits after this time. Increased aphid mortality coincided with a change in physiology of sugar beet leaves from being net sinks to sources of assimilate. Aphids which fed on older leaves, irrespective of plant age, suffered greater mortality than those feeding on young heart leaves. The incidence of dark deposits in aphid stomachs associated with this mortality was greater on outer than on inner leaves of old, mature and young plants. It is suggested that the incidence of the dark deposit is an indicator of declining plant quality. The consequences of this for the spread of beet yellowing viruses are discussed.
Partitioning two‐ and three‐trophic‐level effects of resistant plants on the predator, Nabis roseipennis
Authors: Pfannenstiel R.S. , Yeargan K.V.
Published: October 2003

Two‐ and three‐trophic‐level effects of resistant soybean plants on the development and fecundity of the predator Nabis roseipennis Reuter (Hemiptera: Nabidae) were determined. The nabids, like many hemipteran predators, feed on plants as well as arthropod prey. The life history traits of N. roseipennis when feeding on Pseudoplusia includens (Hübner) (Lepidoptera: Noctuidae) fed the resistant soybean cultivar PI 229358 or the susceptible Cobb' and while exposed to these resistant and susceptible soybean cultivars or a no‐plant control were determined. Nymphal survival of N. roseipennis was unaffected by either prey or plant treatment. Development time was extended and fecundity of N. roseipennis was reduced by feeding on prey fed the resistant plant but not by exposure to resistant soybean plants. Thus, three‐trophic‐level effects of the resistant cultivar PI 229358 on prey quality were more important than two‐trophic‐level effects of direct plant feeding on development and fecundity of N. roseipennis. Consistency of these results with those of other predatory hemipterans and the potential impact of diet composition on the effects of resistant plants are discussed.
Copulation behaviour of Lygocoris pabulinus under laboratory conditions
Authors: Groot Astrid T. , van, der Wal Erna , Schuurman Antje , Visser J. Hans , Blommers Leo H.M. , van Beek Teris A.
Published: October 2003

As a prerequisite to the elucidation of the sex pheromone of the green capsid bug Lygocoris pabulinus (L.), we studied the bug's reproductive development and behaviour. When kept under long‐day conditions (L18:D6) at 25 °C, both males and females start to copulate 4 days after the final moult. Second matings occur in some females, even on consecutive days. The premating period is 10 min on average and copulation lasts 1 to 2 min. At long range, when males are attracted to traps baited with live females, we did not observe a specific calling position of the females. At short range, a characteristic courtship behaviour of the females was not observed either. Males showed a characteristic vibration of the abdomen, which was repeated several times before copulation. This behaviour can be used as a bioassay to test potential sex pheromone compounds.
The circadian rhythm of sperm release in the codling moth, Cydia pomonella
Authors: Giebultowicz Jadwiga M. , Brooks Nicole L.
Published: October 2003

The release of sperm bundles from testes to the vas deferens is controlled by a circadian clock in several moth species. We investigated the pattern of sperm release in the codling moth, Cydia pomonnella L. (Lepidoptera: Tortricidae). Sperm release in the codling moth follows a two‐step rhythm in light‐dark cycles: sperm is released from the testis before lights‐off, remains in the vas deferens during the dark phase and is transferred to the seminal vesicles after lights‐on. This rhythm continues in constant darkness indicating that it has a circadian nature. The release of sperm is asynchronous in moths held in constant light. In contrast to previously investigated moths, constant light has no adverse effects on the male reproductive capacity in the codling moth.
Volatile cues used by the parasitoid, Aphytis melinus, for host location: California red scale revisited
Authors: Morgan David J.W. , Hare J. Daniel
Published: October 2003

Aphytis melinus DeBach (Hymenoptera: Aphelinidae) is a biological control agent of diaspidid scale insects. The parasitoid has a narrow host range but its hosts are polyphagous. We determined the source of volatile cues the wasp uses to locate its few host species when those hosts occur on more than one host plant species. We addressed four questions in regard to the use of volatile cues in host location of California red scale, Aonidiella aurantii (Maskell) (Homoptera: Diaspididae): (1) Does A. melinus use volatile cues to assist in host location? (2) Are these cues innately recognized or learned? (3) Are cues produced by female California red scale, or from other sources? (4) Are the cues specific to the host or host plant? These questions were tested through the use of a Y‐tube olfactometer. Female A. melinus used volatile cues to orient toward both infested and uninfested host plant material. Wasps learned these cues by associating odors from the host plant with host presence. They had no innate preferences for scale insect or host plant volatile stimuli. Contrary to previous studies, we found no evidence of orientation toward the female‐produced sex pheromone of California red scale, nor to volatile cues from the attacked host stage. Wasps given experience with scale insects growing on lemon fruit subsequently oriented toward lemon and orange fruit and leaves. The scale species with which the wasp was given experience did not affect this preference. Wasps given experience with California red scale growing on squash did not orient toward infested lemon fruit. The host ranges of the parasitoid and its hosts are used to explain the adaptive value for the evolution of learned rather than fixed responses to cues used in foraging behavior.
Differential ovicidal and larvicidal resistance to benzoylureas in the codling moth, Cydia pomonella
Authors: Sauphanor Benôit , Brosse Veronique , Monier Catherine , Bouvier Jean C.
Published: October 2003

French populations of the codling moth Cydia pomonella (L.) (Lepidoptera, Tortricidae), a major pest in apple and pear orchards, have developed resistance to different classes of insecticides including the benzoylurea diflubenzuron, a chitin synthesis inhibitor. Ovicidal tests performed on two susceptible strains and one strain selected for its resistance to diflubenzuron revealed the same order of magnitude in resistance ratios to this compound (30‐fold) and two other benzoylureas teflubenzuron and flufenoxuron (22‐ and 11‐fold, respectively). Field rates of these three compounds induced a 45–55% decrease in hatching in the resistant strain, compared to over 90% in the susceptible insects. Despite a 52‐fold ovicidal resistance ratio to the juvenile hormone analog fenoxycarb, this compound induced a 85% decrease in hatching in the resistant strain. Conversely the newly hatched larvae of the resistant strain exhibited a 45 000‐, 33‐ and 2.1‐fold resistance ratio to diflubenzuron, teflubenzuron and flufenoxuron, respectively. The latter value was not significant, and the field rate of flufenoxuron killed over 97% of the resistant larvae while diflubenzuron had no effect. This lack of relationship between ovicidal and larvicidal resistance may be due to different transport properties together with differential enzymatic metabolization. Our results may limit the validity of substitution instars, which approach is frequently used for resistance monitoring. More importantly for resistance management, the resistance of different target instars to each compound has to be considered when establishing control strategies.
Population growth and persistence when prey is diminishing in single‐species and two‐species systems of the predatory mites Euseius finlandicus, Typhlodromus pyri and Kampimodromus aberrans
Authors: Schausberger Peter
Published: October 2003

Population growth and persistence of Euseius finlandicus (Oudemans), Typhlodromus pyri Scheuten and Kampimodromus aberrans (Oudemans) (Acari: Phytoseiidae) were studied in single‐species and two‐species systems on apple seedlings primarily infested by Panonychus ulmi Koch (Acari: Tetranychidae) in an environmentally controlled greenhouse. During the experiment, the seedlings developed natural infestations by Tetranychus urticae Koch (Acari: Tetranychidae), Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), and powdery mildew. Several weeks after the start of the experiment a condition of diminishing prey availability was created by use of hexythiazox treatments. Without heterospecific competitors, T. pyri attained a higher population level than E. finlandicus or K. aberrans when similar amounts of food (spider mites) were available to each. Population growth of T. pyri was decisively favoured by the presence of T. urticae. In the single‐species systems each predatory species persisted to the end of the experiment in spite of diminishing prey. In two‐species systems with T. pyri/E. finlandicus and T. pyri/K. aberrans that were started with the same number of individuals of each species, only T. pyri was left at the end of the experiment. Typhlodromus pyri became more numerous than the other species when prey was abundant (which was in accordance with the results of the single‐species groups) and finally displaced E. finlandicus and K. aberrans towards the end of the experiment. The following factors may have contributed to the dominance of T. pyri: (1) the ability of adult females to survive longer without food than those of E. finlandicus and K. aberrans, (2) the ability to complete juvenile development and to sustain reproduction with phytoseiid prey and (3) an advantage in foraging behaviour over K. aberrans and E. finlandicus at low spider mite levels. Euseius finlandicus predominated in the two‐species system E. finlandicus/K. aberrans, but both species persisted to the end of the experiment.
Species and habitat races in the chrysomelid Galerucella nymphaeae species complex in northern Europe
Authors: Nokkala Christina , Nokkala Seppo
Published: October 2003

The taxonomically controversial Galerucella nymphaeae species complex (Coleoptera, Chrysomelidae) contains at least two distinct species in northern Europe, G. nymphaeae (L.) consuming Nuphar luteum, and G. sagittariae (Gyll.), living mainly on Comarum palustre in southern Finland and on Rubus chamaemorus in northern Finland. By analyzing chromosomal polymorphisms in sympatric populations of G. nymphaeae and G. sagittariae, it was shown that the two species do not hybridize in nature. Chorion polypeptide analysis revealed fixed genetic differences between the two species. However, differences between species must be small, since hybridization is easily induced in the laboratory and F1 hybrids are fertile. Larvae of G. sagittariae cannot survive on Nuphar, and those of G. nymphaeae survive very poorly on Comarum and Rubus. Adults of G. sagittariae from Comarum or Rubus do not choose between these two food plants in laboratory conditions regarding dwelling, egg laying or feeding, but their avoidance of Nuphar is complete. Galerucella nymphaeae clearly prefers Nuphar, but may occasionally also sit, lay eggs or feed on terrestrial plants. It is suggested that G. nymphaeae and G. sagittariae represent sibling species and that the two forms of G. sagittariae, one feeding on Comarum and the other one on Rubus, are habitat races adapted to semiaquatic and terrestrial habitats, respectively. Adaptation to different habitats has created an effective premating barrier to gene flow, supporting the possibility that a sympatric mode of divergence has been involved in habitat race formation and speciation in the species complex.
The effects of physiological factors and host plant experience on the ovipositional activity of the sweet potato whitefly, Bemisia tabaci
Authors: Veenstra Klaas H. , Byrne David N.
Published: October 2003

Both egg load and levels of vitellogenin and vitellin increased when Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), were deprived of host plants. These increases resulted in significant increases in rates of oviposition. There was no difference in total fecundity between whiteflies temporarily deprived of hosts and a control treatment that had continuous access to hosts. The results of previous exposure to a preferred host, melon (Cucumis melo), and a non‐preferred host, cotton (Gossypium hirsutum), were also examined. B. tabaci deposited significantly more eggs during a 6‐h period on melon than on cotton, regardless of host species they were previously confined to. In addition, whiteflies previously exposed to cotton, deposited more eggs than females previously exposed to melon. This higher rate of oviposition resulted in a low egg load as well as lower levels of vitellogenin and vitellin. Conversely, a low rate of oviposition led to high egg load and high levels of vitellogenin and vitellin. Individuals from the same treatment exhibited variation in egg load, which was negatively and significantly correlated with previous oviposition activity. We conclude that the effects of previous host plant exposure on oviposition were, in part, due to behavioral differences that are not related to the reproductive physiology.
The influence of size and duration of aphid infestation on host plant quality, and its effect on sugar beet yellowing virus epidemiology
Authors: Williams Iain S. , Dewar Alan M. , Dixon Anthony F.G.
Published: October 2003

This paper studies the influence of previous infestation on the host quality of sugar beet (Beta vulgaris L.) for aphids and the influence of previous infestation on sugar beet yellowing virus epidemiology. Sugar beet previously infested with Myzus persicae (Sulzer) or Aphis fabae Scopoli (Homoptera: Aphididae) had an improved host quality for subsequently infesting aphids of the same species. There was a significant negative relationship between the number of M. persicae infesting a plant and the proportion of those that died with a dark deposit in their stomachs, and a significant positive relationship between the number that settled on a plant and the number that infested it previously. Nymphs feeding on previously infested plants grew more rapidly than those on control plants. The beneficial effect of previous infestation persisted for at least 2 weeks and prolongation of the infestation beyond 2 weeks was of no further benefit to the aphids. Field grown sugar beet, previously colonised by M. persicae, was more susceptible to natural infestation by M. persicae up to 5 days after exposure. Previously infested plants were also more susceptible to infection with beet mild yellowing virus (BMYV) but not beet yellows virus (BYV), suggesting that the aphids on the previously infested sugar beet settled more readily and were more inclined to feed (and thus transmit BMYV) than aphids on the previously uninfested plants. The consequences for the control of sugar beet yellowing virus vectors are discussed.
Potential for intraguild predation and competition among predatory Coccinellidae and Chrysopidae
Authors: Phoofolo Mpho W. , Obrycki John J.
Published: October 2003

In a laboratory study two coccinellid species, Coleomegilla maculata (DeGeer) and Harmonia axyridis Pallas, completed preimaginal development on lacewing eggs, Chrysoperla carnea Stephens or pea aphids, Acyrthosiphon pisum (Harris) in similar times. Preimaginal survival on C. carnea eggs was similar to survival on A. pisum for all stages of C. maculata and H. axyridis. Coccinellid adults that developed on C. carnea eggs were smaller than adults reared on A. pisum. Coccinella septempunctata L. did not complete preimaginal development on C. carnea eggs. Chrysoperla carnea preimaginal developmental time was approximately 20 days when fed either C. maculata eggs or A. pisum. Chrysoperla carnea fed C. maculata eggs developed into smaller adults, compared to adults reared as larvae on A. pisum, Ostrinia nubilalis (Hübner) eggs, or A. pisum alternated daily with O. nubilalis eggs. C. carnea did not complete preimaginal development on H. axyridis eggs. Cannibalism occurred more frequently between C. carnea third instars than between C. maculata fourth instars. When a C. carnea third instar was paired with a C. maculata fourth instar, more C. maculata were preyed upon by C. carnea, regardless of the herbivorous prey density. In the field these two predator species may negatively affect each other and reduce their suppression of pest densities.
Host plant selection and development in Spodoptera exigua: do mother and offspring know best?
Authors: Berdegué Mariano , Reitz Stuart R. , Trumble John T.
Published: October 2003

We examined the ovipositional preference and larval development of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) on two common hosts in southern California, Chenopodium murale L. (Chenopodiaceae) and Apium graveolens L. (Umbelliferae) to determine if female oviposition preference is correlated with offspring performance. Greenhouse oviposition choice tests indicated that S. exigua oviposit more frequently on C. murale than on A. graveolens. However under laboratory conditions, larvae reared on C. murale had longer development times, lower relative growth rate, and lower survivorship than larvae reared on A. graveolens. larval and pupal masses were significantly greater on A. graveolens than on C. murale. Furthermore, pupal masses were significantly greater for individuals reared on A. graveolens than on C. murale. Because pupal masses and adult fecundity are positively correlated for Spodoptera spp., the fitness of S. exigua on A. graveolens is likely to be substantially higher than its fitness on C. murale. Despite better larval performance on A. graveolens, previous results from choice tests with whole plants and leaf discs indicate that the highly mobile S. exigua larvae strongly prefer C. murale over A. graveolens. Hypotheses attempting to explain this lack of correlation between larval and adult host preference versus development and survival in this system are discussed.