bluuebunny/crossref_metadata_2025_split huggingface dataset:
Change in foraging behaviour of the predatory mite Phytoseiulus persimilis after exposure to dead conspecifics and their products
Authors: Schütte Conny , van Baarlen Peter , Dijkman Herman , Dicke Marcel 
Published: October 2003

AbstractAdult females of the predatory mite Phytoseiulus persimilis Athias‐Henriot are strongly attracted to infochemicals released by plants infested with their prey, the two‐spotted spider mite (Tetranychus urticae Koch), thereby effectively locating their prey. However, we found a consistently lower degree of attraction to these infochemicals for a population of P. persimilis, which is called non‐responding population. Here we demonstrate that this low degree of attraction is a contagious phenomenon and that it cannot be explained by differences in abiotic conditions, physiological state and experience of predators or by genetic differences between predator populations. Female predators exposed to dead conspecifics of the non‐responding population and their products showed a lower degree of attraction to plant odours and a higher mortality than predators exposed to products of a living conspecific of the non‐responding population. This was true 6–7 days after contact with dead conspecifics and their products whereas 2 days after contact no effects were detected. The present results are discussed in view of our hypothesis that the change in foraging behaviour as well as the high mortality rate are symptoms of a contagious disease affecting the non‐responding population.
Behaviour of pink bollworm males near high‐dose, point sources of pheromone in field wind tunnels: insights into mechanisms of mating disruption
Authors: Cardé Ring T. , Staten Robert T. , Mafra‐Neto Agenor 
Published: October 2003

AbstractThe mechanisms by which the application of formulated pheromone interferes with mating in the pink bollworm moth (PBW), Pectinophora gossypiella were examined in 0.4 ha cotton fields using high‐dose (78 mg A.I.) sealed polyethylene dispensers. Walk‐in, field wind tunnels 6.2 m long were placed over two rows of cotton. Treatments consisted of a control, a tunnel in a field free of disruptant formulation; a 3‐rope treatment, in which the field was free of pheromone but one of the cotton rows in the wind tunnel was treated with 3 PBW ropes; and a rope‐grid treatment, in which the field was treated with PBW ropes at the standard density of 1000 ha−1 and one of the cotton rows inside the wind tunnel was treated with 3 PBW ropes. We released marked males into the tunnels near sunset or held them in field cages for 24 h prior to assay. Two pheromone traps at the tunnel's upwind end monitored the ability of males to locate point sources of pheromone. In the 3‐rope tunnel, traps placed upwind of the cotton row treated with disruptant pheromone captured far fewer males than those placed upwind of the untreated cotton row. In the tunnel situated in the centre of the rope‐gridded field, very few males were caught in traps in both rows, indicating a camouflage of the pheromone plumes from the traps by the background of airborne disruptant drawn into the tunnel from the field. Activity of moths near the synthetic pheromone sources was video‐recorded. Males oriented to, landed on or near, and walked on or near, PBW ropes, indicating competition between pheromone sources as a mechanism of mating disruption. Most males visiting PBW ropes became quiescent or disappeared from the field of view after a few minutes, suggesting a habituation/adaptation of response. The rhythm of attraction of males held in the field for 24 h before release was comprised of a small peak of activity near 2000 h, with the majority of attraction between 2300 and 0300 h. Much of the attraction before 0100 appears to be an advancement of the male's normal diel rhythm, caused by the presence of disruptant. Together these findings indicate that mating disruption of pink bollworm using the PBW ropes is achieved by a combination of mechanisms: a camouflage of natural plumes, competition between pheromone sources, habituation, and some advancement of the male's rhythm of response.
Rapid adaptation of squash bug, Anasa tristis, populations to a resistant cucurbit cultivar
Authors: Margolies David C. , Nechols James R. , Vogt Elizabeth A. 
Published: October 2003

AbstractWe conducted laboratory experiments on two field‐collected populations of the squash bug, [Anasa tristis (De Geer) (Hemiptera: Coreidae)], to compare their responses to five generations of selection on a resistant squash cultivar ‘Waltham Butternut’, a susceptible cultivar ‘Early Prolific Straightneck’, or alternating generations on the resistant and susceptible cultivars. Before testing, one population was maintained for 1 generation on susceptible squash plants, while the other was maintained on the same cultivar for 5 generations. In both populations, nymphal survival decreased markedly in the first generation on resistant squash, but then approximately doubled in the second generation reared on the resistant cultivar. By the end of the experiments, survival on the rearing host was the same for A. tristis maintained continuously on a single cultivar, regardless of which cultivar. Immediately following one or more generations on resistant plants, A. tristis nymphs had lower survival on the susceptible cultivar than did nymphs that had been maintained for consecutive generations on the susceptible cultivar. Results of reciprocal crosses between lines of A. tristis reared on either resistant or susceptible squash for five generations indicated a genetic basis for differences in nymphal survival on the two cultivars.In contrast with the changes in nymphal survival, the preoviposition period became progressively longer when A. tristis was reared for several generations on the resistant cultivar compared to the susceptible one. Prior rearing on resistant plants increased the preoviposition period of adults placed on susceptible plants. However, adult feeding on resistant plants following nymphal development on susceptible plants did not result in an increase in the preoviposition period on resistant plants. Our findings indicate that squash bugs can adapt to resistant plants within a relatively short period in the laboratory. However, ecological and agricultural factors should prevent squash bugs from overcoming resistance in the field.
Durability of brown planthopper, Nilaparvata lugens, resistance in rice variety IR64 in greenhouse selection studies
Authors: Alam Syed N. , Cohen Michael B. 
Published: October 2003

AbstractColonies of brown planthopper, Nilaparvata lugens (Stål), established from three locations on Luzon Island, Philippines, were selected for adaptation to four rice varieties: IR22 (no major resistance genes), IR26 (Bph1 gene), IR64 (Bph1 and additional moderate resistance from minor genes), and IR72 (Bph3). In each of the first eleven generations, and the fifteenth generation, the fitness of N. lugens from subcolonies reared on each of the varieties was measured with four tests: survival to adult, feeding rate, female weight, and developmental time. In three of the four tests, insects from all three locations showed slower adaptation to IR64 than to IR22, IR26, and IR72. In the fourth test, developmental time, the rate of adaptation on IR64 and IR72 was similar, and both varieties retained a significant level of resistance after 15 generations of selection. However, as measured by survival to adult, feeding rate, and female weight, after 15 generations the fitness on IR64 of N. lugens from two locations no longer differed from those on other varieties. In these two locations, Central Luzon and IRRI, IR64 has been widely grown for 10 years. After 15 generations of selection IR64 remained resistant to insects from Banaue, an isolated location where modern resistant varieties are not grown, as measured by all four tests. Our results demonstrate that the relatively greater durability of brown planthopper resistance in IR64, which has been suspected on the basis of its performance in the field, is also evident under greenhouse conditions in the absence of natural enemies and other mortality factors.
The relative performance of pheromone and light traps in monitoring the seasonal activity of both sexes of the eastern hemlock looper, Lambdina fiscellaria fiscellaria
Authors: Delisle Johanne , West Richard John , Bowers Wade Woodrow 
Published: October 2003

AbstractThe seasonal flight activity of both sexes of the eastern hemlock looper, Lambdina fiscellaria fiscellaria Guenée (Lepidoptera: Geometridae) was studied during two consecutive years in Quebec and Newfoundland, using light (L), pheromone (P) and combined light and pheromone (LP) traps. Moth density significantly affected the performance of the different traps, with P traps being more effective at low than high density. However, P trap catches decreased just prior to the onset of female captures, probably as a result of competition between traps and virgin calling females. Nearly all females caught in L and LP traps were already mated and even the first females caught had laid at least half of their egg complement. In Quebec under warm nights, the pattern of male activity occurred at different times, with peak P catches being later in the scotophase than those of L traps, but overall similar numbers of males were caught in both traps. In contrast, under cool nights, males were caught early in the night in both P and L traps, suggesting a strong competition effect between traps, although more males were caught in P than L traps overall. In Newfoundland, the pattern of male captures in L and P traps was similar at both high and low temperatures, so competition between trap types would always be high. Under these conditions P traps were more effective than L traps. Irrespective of the region, year or temperature, significantly more males were captured in LP, with the effect of L and P being additive. In both regions, females responded similarly to L and LP traps with peak activity occurring early in the night. Captures of females were lower than those of males under cool temperatures, suggesting that the temperature threshold for flight is higher for females. The use of L and P traps simultaneously and/or in combination is discussed in relation to integrated pest management programs and ecological considerations.
Reduction of insect cold‐hardiness using ice‐nucleating active fungi and surfactants
Authors: Lee Marcia R. , Lee Richard E. , Strong Janet M. , Minges Stacey R. , Mugnano John A. 
Published: October 2003

AbstractThe supercooling point (SCP) of an insect model, the lady beetle Hippodamia convergens Guérin‐Menéville (Coleoptera, Coccinellidae) was markedly elevated by treatment with aqueous suspensions of the filamentous, ice nucleation active (INA) fungi Fusarium avenaceum and slightly elevated by Fusarium acuminatum. Addition of the surfactant Tween 80 to the fungal suspensions further reduced the supercooling capacity of adult beetles. When used alone the surfactant Triton X‐100 produced a greater SCP elevation than Tween 20 or Tween 80. The emulsifier gum arabic was ineffective in elevating beetle SCPs when applied alone and when added to INA fungal preparations it decreased their efficacy. Aqueous suspensions of both viable sporulating and viable pleomorphic (a permanent, degenerative, nonsporulating cultural state) forms of both fungal species were more effective in elevating the SCP than killed preparations except for the pleomorphic F. acuminatum suspension in which the killed form was slightly more active. Application of INA fungi applied in combination with surfactants may be useful in the development of methods for the biological control of overwintering freeze‐susceptible insect pests by decreasing their capacity to avoid lethal freezing by supercooling.
Interaction of treatment of both adult and immature Coleoptera with a chitin synthesis inhibitor affects mortality and development time of their progeny
Authors: Elek Jane A. 
Published: October 2003

AbstractChitin synthesis inhibitors, like many other insect growth regulating insecticides, do not kill adult insects but cause mortality of the immature stages. Pre‐exposure of adult stored grain Coleoptera, Rhyzopertha dominica (F.) (Bostrichidae) and Sitophilus oryzae (L.) (Curculionidae) and development of their progeny in grain treated with the chitin synthesis inhibitor, chlorfluazuron, influenced the mortality and development rate of the progeny. Hatch rate of eggs from R. dominica adults that had both developed and laid on wheat treated with 0.75 mg kg−1 chlorfluazuron was reduced by almost 50% compared with untreated eggs, with an LC50 of 0.84 mg kg−1. Eggs laid on treated wheat by R. dominica adults that had been exposed only to treated wheat for 2 weeks before oviposition showed greater reduction in hatch: 75% reduction of normal hatch rate at 0.25 mg kg−1 and almost 100% reduction at 2 mg kg−1 chlorfluazuron, with an LC50 of 0.19 mg kg−1 chlorfluazuron. X‐rays were used to monitor the development and mortality of the immature stages of S. oryzae that developed within the wheat grains. Numbers of eggs laid were not affected by chlorfluazuron treatment. The combination of pre‐exposure of adults and chlorfluazuron concentration had an additive effect on mortality of immature S. oryzae. Pre‐exposure of adults caused most mortality in the first three weeks of development (eggs and larvae), whereas development in treated wheat caused mortality from weeks 3 to 8 (pupae and adults); higher concentrations of chlorfluazuron caused higher mortality. Development in wheat treated with 1 mg kg−1 chlorfluazuron caused 12% corrected overall mortality of progeny while pre‐exposure to the same concentration and development in untreated wheat caused 29% corrected mortality. Pre‐exposure combined with development in wheat treated with 1 mg kg−1 caused 30% corrected mortality. Thus, pre‐exposure of adults appears to have a greater effect on mortality of S. oryzae progeny than development of immature stages in treated grain. Development on treated grain had no effect on development rate. Pre‐exposure of adults did not appear to affect the rate of immature development, as assessed by X‐rays, but did slow the emergence of adults, lengthening development time by about 2 days. This significant, additive effect of pre‐exposure of adults on the mortality of their progeny will enhance the toxicity of chitin synthesis inhibitors such as chlorfluazuron, since most adults receive treatment when the immature stages are treated in crops either before they are harvested or in storage. Assessing the proportion of eggs that hatch from pre‐exposed adults would be a simpler bioassay for CSIs.
Intrinsic rate of population increase of the spider mite Tetranychus urticae on the ornamental crop gerbera: intraspecific variation in host plant and herbivore
Authors: Krips O.E. , Witul A. , Willems P.E.L. , Dicke M. 
Published: October 2003

AbstractEight cultivars of the ornamental crop Gerbera jamesonii Bolus (Asteraceae) were compared in host plant suitability for the two spotted spider mite Tetranychus urticae Koch (Acarina: Tetranychidae). This was done by determining the intrinsic rate of population increase, rm, of spider mites on leaf discs of plants from each of the cultivars. Large differences in rm values were found, ranging from 0.088/day on cultivar Bianca to 0.242/day on cultivar Sirtaki. This variation in rm was mainly caused by differences in developmental time of the spider mites.We assessed the performance of spider mites on young and old leaves of the two gerbera cultivars Bianca and Sirtaki. On Sirtaki the spider mites had a shorter developmental time and higher peak oviposition rate on young leaves than on old leaves. However, on Bianca such an effect was not found.We also determined the performance of two spider mite strains on the resistant gerbera cultivar Bianca. We compared the rm of a strain that had been reared on this cultivar for approximately half a year with the rm of a strain that was reared on bean. The rm of the strain that was reared on cultivar Bianca increased to 0.208/day, which is however still substantially lower than the rm on the susceptible cultivar Sirtaki.
An evaluation of (Z)‐9‐tricosene and food odours for attracting house flies, Musca domestica, to baited targets in deep‐pit poultry units
Authors: Chapman Jason W. , Knapp Jennifer J. , Howse Philip E. , Goulson Dave 
Published: October 2003

AbstractField trials investigating the effect of food baits on catches of Musca domestica at toxic targets impregnated with the female sex pheromone, (Z)‐9‐tricosene, were conducted in a caged‐layer deep‐pit poultry unit in southern England. Targets treated with an Alfacron‐sugar mixture and baited with 2.5 g of 40% (Z)‐9‐tricosene beads caught significantly greater numbers of both male and female M. domestica than control targets. Egg and milk‐baited targets were less attractive than controls, while brewers yeast slightly increased the numbers of M. domestica attracted. However, the inclusion of brewers yeast in (Z)‐9‐tricosene‐impregnated targets produced a significant reduction in the number of male M. domestica attracted. Increased female attraction was elicited by baiting the targets with 2‐phenylethanol, at the quantities of 1 mg and 10 mg. However, 2‐phenylethanol had no effect on female attraction when presented in conjunction with (Z)‐9‐tricosene. The implications of these results in relation to the control of M. domestica populations in poultry units are discussed.
Diapause survival and post‐diapause performance in bumblebee queens (Bombus terrestris)
Authors: Beekman M. , van Stratum P. , Lingeman R. 
Published: October 2003

AbstractDiapause survival and post‐diapause performance (i.e., if a queen starts to lay eggs) of in total 2210 bumblebee queens (Bombus terrestris) were measured under different diapause regimes: 5 temperatures (−5, 0, 5, 10 and 15 °C) in combination with 5 durations of exposure (1, 2, 4, 6 and 8 months).The results show that weight at the start of diapause determines to a large extent whether a queen will be able to survive diapause. Queens with a wet weight below 0.6 g prior to diapause did not survive, but for those queens exceeding this threshold a higher pre‐ diapause weight did not increase their post‐diapause performance.There was no effect of temperature on diapause survival; 76% of the variance in survival could be explained by the duration of the treatment. Neither temperature nor duration of exposure had an effect on post‐diapause performance. The preoviposition period of the queens that laid eggs was also determined. The preoviposition period was affected by both temperature and duration of exposure: the preoviposition period decreased with decreasing temperature but also with increasing duration of the treatment.
Settling behaviour and reproductive potential of the green peach aphid Myzus persicae on peach varieties and a related wild Prunus
Authors: Sauge Marie‐Hélène , Kervella Jocelyne , Pascal Thierry 
Published: October 2003

AbstractDiscovery in the late seventies of resistance to the green peach aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) in Prunus species was based on screening in the field or in greenhouses with natural aphid populations. Here, we assess the impact of these wild and domesticated peach trees on the behaviour, development, reproductive performance and demography of cloned aphids under controlled light and temperature. Four peach varieties, i.e., Rubira, Weeping Flower Peach, Summergrand and Malo konare and the clone P1908 of the related species Prunus davidiana were tested against the highly susceptible cultivar GF305. Besides a variability in the performance of aphids among experiments, our results showed that (i) distinct mechanisms were involved in the sources of resistance studied and (ii) the ranking of the genotypes on their resistance/susceptibility status remained roughly stable throughout the experiments. Observations on the settling behaviour of first instar nymphs demonstrated antixenosis components in the resistance conferred by Rubira and Weeping Flower Peach. Nymphs began to leave the plants after a short exposure (19–21 h) and no aphid was left after 4 days. Nymphal mortality remained rather low (16%) compared to the repellent effect on aphids of both genotypes. Nymphs disappeared from Weeping Flower Peach significantly earlier than from Rubira. Summergrand, Malo konare and P. davidiana clone P1908 were accepted as host plants by aphids. On P. davidiana, decreased fecundity and intrinsic rate of natural increase (rm= 0.20, averaged on all experiments) were clear expression of antibiosis. In addition, the mean length of the mature embryos within the gonads of the females on the day of adult moult was negatively correlated with the total number of embryos, providing evidence that aphids on this genotype lacked sufficient ressources to be directed both towards production and growth of embryos. Compared to the most susceptible cultivar GF305 (rm= 0.36), Summergrand (rm= 0.26) and Malo konare (rm= 0.28) had, to a lesser extent, a negative impact on nymph production and rate of increase.
Hyperparasitism by an exotic autoparasitoid: secondary host selection and the window of vulnerability of conspecific and native heterospecific hosts
Authors: Hunter Martha S. , Kelly Suzanne E. 
Published: October 2003

Abstract Encarsia transvena is an ‘autoparasitoid’ in the hymenopteran family Aphelinidae. In this species, female eggs are laid in whitefly nymphs. Male eggs are laid externally on immature parasitoids enclosed within the whitefly integument, either their own species, or other primary parasitoids. We explored parasitism by E. transvena of conspecific female immatures and those of a native primary parasitoid, Eretmocerus eremicus, in laboratory experiments. In the first experiment, female E. transvena were offered different combinations of two stages of E. transvena (late larvae – prepupae (ET2), and early pupae (ET3)), and one stage of E. eremicus (prepupae – early pupae (EE2)) in paired choice tests. The results indicated very little parasitism of ET3 relative to the host it was paired with, either EE2 or ET2. However, when EE2 was offered with ET2, there was no statistically significant difference in parasitism. In a no‐choice experiment in which oviposition patterns and male progeny development were examined in four stages of both species of wasp, clear differences were observed between the host species. Only one stage of E. transvena (ET2) was parasitized and supported development of male E. transvena to any significant degree. In contrast, in E. eremicus, EE2, EE3 (red‐eyed pupae), and EE4 (late pupae) were all parasitized, and male E. transvena emerged from all three stages, although fewer males emerged from EE4. In both species, wasp larvae that were still enclosed within the wet whitefly remains (ET1 and EE1) were parasitized at a very low rate. Lastly, an experiment that determined the length of the later developmental stages of E. transvena and E. eremicus suggested that the duration of the period in which E. transvena is susceptible to parasitism by conspecific females is less than half the period of susceptibility of E. eremicus. These results taken together suggest the potential for interference of E. eremicus by E. transvena, but other factors not examined here may also influence the outcome of interactions in the field.