bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interspecific competition between two parasitoids of Helicoverpa zea: Eucelatoria bryani and E. rubentis
Authors: Reitz Stuart R. 
Published: March 2011

AbstractMultiple parasitism of Helicoverpa zea (Lepidoptera: Noctuidae) had differential effects on the gregarious endoparasitoids Eucelatoria bryani and E. rubentis (Diptera: Tachinidae). Both species were able to survive in multiparasitized hosts. However while the survival of E. bryani was not affected by the presence of E. rubentis, E. rubentis survival was reduced when competing with 24‐h older E. bryani. The presence of E. rubentis did not result in a decrease in the size of E. bryani except when E. rubentis was 24‐h older than E. bryani. The presence of E. bryani tended to result in smaller E. rubentis. The presence of similarly aged heterospecific competitors often resulted in prolonged development time for both species. Naïve females did not alter oviposition between unparasitized and heterospecifically parasitized fifth‐instar larvae of H. zea, either by ovipositing less frequently in parasitized hosts than unparasitized ones, or by reducing clutch size in parasitized hosts. These results indicate that in H. zea, E. bryani is a superior competitor compared with E. rubentis. These factors should be considered in evaluating the potential of E. bryani and E. rubentis as biological control agents of H. zea.
Identity, spatial distribution, and variability of induced chemical responses in tomato plants
Authors: Stout Michael J. , Workman Kathi V. , Duffey Sean S. 
Published: March 2011

AbstractUsing four‐leaf tomato plants (Lycopersicon esculentum Mill) as a model system, we examined the spatial distribution of damage‐induced changes in foliar protein activities. Terminal leaflets of third leaves of tomato plants were subjected to one of four types of damage, and the activities of four putative defenses – polyphenol oxidase, peroxidase, lipoxygenase, and proteinase inhibitors – were determined at four leaflet positions relative to the damaged leaflet. Multiple proteins were differentially induced by the different damage types. For a given damage type, the spatial pattern of induction was different for different proteins. More exhaustive spatial mapping of the polyphenol oxidase response to feeding by Helicoverpa zea Boddie revealed that damaged plants were more variable, both within and between plants, in the activity of this enzyme than undamaged plants. The spatial patterns of induction of these four putative defenses throughout the plant suggest that the induced plant is chemically heterogeneous and that different mechanisms of defense operate in different regions of the plant. These data are critical to an elucidation of cause‐effect relationships between induced chemicals and induced resistance in tomato foliage. In addition, these data suggest that induction functions, in part, to increase chemical variation in tomato plants; the potential role of phytochemical variation in plant defense is discussed.
Characterization of induced resistance in tomato plants
Authors: Stout Michael J. , Duffey Sean S. 
Published: March 2011

AbstractWe have characterized, using several types of bioassays, the resistance induced in young tomato plants by feeding of the corn earworm, Helicoverpa zea. Beet armyworm larvae, Spodoptera exigua, and leafminers, Liriomyza trifolii, were used to assay the induced resistance. In whole‐plant experiments, damage localized to a single leaflet of four‐leaf tomato plants induced a systemic increase in resistance such that beet armyworm larvae confined to previously damaged (induced) plants grew at a rate about half that of larvae raised on control plants and consumed less leaf tissue from induced plants than from control plants. In experiments using excised leaves, beet armyworm larvae suffered increased mortality when reared on leaves from induced plants. The strength of this induced resistance varied spatially relative to the damaged position; moreover, the spatial distribution of induced resistance changed over a three‐week period following damage. Other experiments demonstrated that the mechanism of induced resistance in tomato foliage involves both a decrease in larval preference for and a decrease in the nutritional value of induced foliage. Induction also retarded the oviposition and/or early development of leafminers. Thus, induced resistance has relatively severe effects on the biology of subsequent herbivores. These data should allow us to begin to elucidate cause‐effect relationships between induced resistance and induced chemistry in tomato plants.
Effects of temperature, multiple allelochemicals and larval age on the performance of a specialist caterpillar
Authors: Yang Yuelong , Stamp Nancy E. , Osier Tod L. 
Published: March 2011

AbstractTo understand the mechanisms underlying plant‐insect herbivore interactions, it is necessary to examine the simultaneous effects of temperature, food quality and larval age. We examined the simultaneous effects of three allelochemicals (tomatine, rutin and chlorogenic acid) on the performance of first and second instar Manduca sexta larvae under two representative thermal regimes 21: 10°C and 26: 15°C for spring and summer, respectively. Thermal regime and allelochemicals interacted to influence the time from egg hatch to ecdysis to the third instar. On average, it took about half as much time to reach the third instar at 26: 15°C as it did at 21: 10°C. Separately, tomatine and rutin had a negative effect on developmental time from egg hatch to the third instar, but their simultaneous effects were not additive. Chlorogenic acid significantly reduced the negative effect of tomatine. The magnitude of the allelochemical effect was larger at the cooler thermal regime compared to the warmer regime. For instance, chlorogenic acid by itself had no effect at the 26: 15°C regime, but at the 21: 10°C regime it significantly shortened total developmental time. The effect of chlorogenic acid on stadium duration was distinctly different for the two instars. Chlorogenic acid shortened stadium duration of first instar larvae. However, depending on thermal regime and the presence of tomatine, chlorogenic acid had a negative, positive or neutral effect on stadium duration of second instar larvae. Molting duration of second instar larvae was shortened by a half day at the warmer thermal regime but was not affected by the allelochemicals. Final larval weight was influenced by rutin and chlorogenic acid. Caterpillars fed diets containing 20 μmoles of rutin were on average 10% lighter than those fed plain diet, whereas those fed diets containing 20 μmoles of chlorogenic adic were on average 7% heavier. However, the effect of chlorogenic acid depended on thermal regime. Overall, our results indicated that: 1) temperature and food quality can interact to influence insect performance and 2) these effects are influenced by larval age.
Chemosensory basis of feeding and oviposition behaviour in herbivorous insects: a glance at the periphery
Authors: VAN Loon Joop J. A. 
Published: March 2011

AbstractRecent advances in our understanding of the relationship between chemosensory and behavioural responses to phytochemicals come from a number of studies on ovipositional and food selection behaviour of flies, butterflies, moths and beetles. Establishing input‐output relationships has provided insight into the way in which the activity of chemoreceptors is translated into host‐plant selection behaviour. This was achieved for both the qualitative contrast acceptance/rejection and for quantifiable preference hierarchies. By now it is clear that the subtlety of coding the complex phytochemical profiles offered by potential host plants relies on across‐fibre patterns or ensemble‐firing of taste neurons. Progress along these lines depends on unravelling processing pathways in the central nervous system, still a largely unexplored area in herbivorous insects. Increased interest can be noted for the mechanisms operating during the most peripheral events of chemoreception: the interaction of phytochemical and chemoreceptor, determining the specificity of recognition. Evidence for ‘peripheral integration’ has accumulated. Deterrent receptors have an especially puzzling nature. Although such cells respond to a wide array of structurally diverse secondary plant metabolites, their sensitivity profile differs between closely related species. To what extent membrane‐bound receptor molecules are involved and what degree of specificity is conferred by these, is largely unknown. Sensitivity to a certain group or class of compounds is determined by single genes in several cases. This allows for a scenario in which single gene mutations affect stimulus‐receptor interactions, which might concurrently affect host‐plant selection behaviour.
Trade‐offs in larval performance on normal and novel hosts
Authors: Thompson John N. 
Published: March 2011

AbstractThe evolution of host specialization in phytophagous insects is generally thought to involve genetic trade‐offs that prevent individuals from maximizing fitness simultaneously on two or more hosts. Several hypotheses, however, have suggested that trade‐offs may not be evident in experiments comparing larval performance on normal and novel hosts. Tests on survivorship, growth rate, and pupal mass among families of the swallowtail butterfly Papilio oregonius on its normal host and on a novel host provide support for these hypotheses, although they do not discriminate among them. Families differed in their relative performance on the hosts, but there was no evidence of a negative genetic correlation between hosts for any of the measures of performance. In addition, there were no correlations among the different measures, corroborating an earlier result suggesting that these different components of performance in the P. machaon species group are under at least partially separate genetic control. These results and similar results published for other insects have now produced a body of studies indicating that genetic trade‐offs in individual components of larval performance may not be a major factor preventing shifts onto novel host plants. Trade‐offs leading to the evolution of host specialization are more likely to involve coordination among the various components of performance together with ecological factors that allow higher fitness on one host than on others.
Diversity and variability of plant secondary metabolism: a mechanistic view
Authors: Hartmann Thomas 
Published: March 2011

AbstractBased upon a brief historical view, the typical features of plant secondary metabolism and its role in chemical interactions between plants and their environment are discussed. Facts and arguments are presented favouring the hypothesis that secondary metabolism evolved under the selection pressure of a competitive environment. The high ‘degree of chemical freedom’ of secondary metabolism which, in contrast to primary metabolism, allows structural modifications with almost no restrictions, is stressed as mechanistic basis for the generation of chemical diversity. Biochemical and physiological properties of secondary metabolism are in accordance with such a view. It is suggested that the great chemical diversity and intraspecific variability of secondary metabolism is the result of processes of natural selection which act upon highly variable chemical structures. This view is exemplified by the pyrrolizidine alkaloids, a typical class of secondary compounds.
Physiology and costs of resistance to herbivory and disease in Brassica
Authors: Mitchell‐Olds T. , Siemens D. , Pedersen D. 
Published: March 2011

AbstractWe used artificial selection experiments to study genetic allocation costs and physiological mechanisms of resistance to herbivory and fungal disease. Genetic costs to resistance were present in some instances and absent in others. Genetic resistance to the fungal pathogen, Leptosphaeria maculans was cost‐free, while resistance to Peronospora parasitica showed a negative genetic correlation between disease resistance and growth rate. Leptosphaeria resistant genotypes had 13% higher chitinase activity. Genetic increases in myrosinase activity were correlated with increased resistance to flea beetles (Phyllotreta cruciferae), but resulted in lower plant fecundity, presumably due to production costs of myrosinase. Genetic costs of resistance may maintain genetic variation in natural plant populations. These studies demonstrate the predictive and explanatory power of a functional approach to plant‐herbivore and plantpathogen interactions.
Electrical penetration graphs of the damson‐hop aphid, Phorodon humuli on resistant and susceptible hops (Humulus lupulus)
Authors: Paul Therasa A. , Darby Peter , Green Colin P. , Hodgson Chris J. , Rossiter John T. 
Published: March 2011

AbstractElectrical penetration graphs (EPG's) were used to locate resistance to Phorodon humuli (Schrank) (Homoptera, Aphididae) in hops (Humulus lupulus, Cannabinaceae). Aphids on those hops showing resistance had a much reduced E2 pattern (uptake of phloem). In addition, many aphids on the resistant plants spent time non‐probing within two minutes of withdrawing from the phloem. This was not observed with aphids on susceptible hops. The results suggest that resistance is located in the phloem. The involvement of a mechanical factor such as the blocking of aphid stylets, the presence of antinutritional factors, or simply an inadequate supply of nutrients, are discussed as possible resistance mechanisms.
Binomial sampling plans for estimating and classifying population density of adult Bemisia tabaci in cotton
Authors: Naranjo Steve E. , Flint Hollis M. , Henneberry Thomas J. 
Published: March 2011

AbstractWe used an empirical relationship to develop models for estimating and for classifying the population density of adult Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) in cotton based on the proportion of infested leaves. We examined models based on tally thresholds (the minimum number of insects present before a leaf is considered infested) of 1, 2, 3, 4, 5, and 6 adults per fifth mainstem node leaf from the terminal. For the estimation of density, sampling precision (SE/mean) increased with higher tally thresholds (T); however, there was negligible improvement in precision with T ≥ 3 adults per leaf. Using T = 3 as few as 30 samples were necessary to achieve a precision of 0.25 over a wide range of population densities. To evaluate these binomial models for the classification of population density for pest management application, we used simulation analyses to determine operating characteristic curves (error probabilities), and to estimate average sample size and cost functions. Error probabilities and average sample sizes declined with higher values of T, but there was negligible decline in error probabilities using T ≥ 3 adults per leaf, and the overall cost of sampling was lowest for T = 3. Wald's sequential probability ratio test was used to formulate sequential sampling stop lines for classifying population density relative to two nominal action thresholds, 5 or 10 adults per leaf. Simulation analysis indicated that by using T = 3, fewer than 30 samples, on average, were needed to classify populations relative to either action threshold. However, simulated error probabilities consistently exceeded the nominal error probabilities used to initially formulate sequential sampling stop lines regardless of the tally threshold. Comparing binomial models using T = 1 or T = 3 to independent data from four field sites, the model for T = 1 was generally biased towards overprediction of mean density, but the T = 3 model was a robust and relatively unbiased predictor of mean density. The binomial sampling plans presented here should permit the rapid estimation of population density and enhance the efficiency of pest management programs based on the prescriptive suppression of B. tabaci in cotton.
Insect‐crop interactions in a diversified cropping system: parasitism by Aleochara bilineata and Trybliographa rapae of the cabbage root fly, Delia radicum, on cabbage in the presence of white clover
Authors: Langer Vibeke 
Published: March 2011

AbstractParasitism of the cabbage root fly, Delia radicum (L.) by the staphylinid Aleochara bilineata Gyllenhal and the cynipid Trybliographa rapae Westwood was examined in a cabbage monoculture and a mixed stand of cabbage undersown with white clover. Number of overwintering cabbage root fly pupae per plant was consistently reduced in the mixed stand, and the incidence of plants attacked by cabbage root fly was either reduced or not different in the mixed stand compared to cabbage monoculture. For both parasitoids, the probability of D. radicum attacked plants having at least one parasitized pupa increased with density of cabbage root fly pupae around the plant. For A. bilineata, this positive relation between presence of parasitism and host density was consistently stronger in cabbage monoculture than in cabbage undersown with clover. Location of a host plant by T. rapae was not consistently affected by the presence of clover. D. radicum attacked plants situated in the cabbage and clover mixture were found by T. rapae as easily as in cabbage monoculture. Overall, the ‘total risk of parasitism’ for a cabbage root fly pupa by A. bilineata was reduced in the mixed stand compared to the cabbage monoculture, whereas the risk of parasitism by T. rapae was not consistently affected by clover. For both parasitoids, intensity of parasitism showed a variable relationship with host density on individual plants attacked by the cabbage root fly. Overall, in spite of consistently lower total density of pupae in the mixed cabbage – clover than in cabbage monoculture, the density of unparasitized pupae was reduced by the presence of non‐host plants only in two of the four experiments. The results emphasize the need to include not only herbivore and crop, but also other plant species as well as natural enemies when evaluating management methods.
Snowdrop and wheatgerm lectins and avidin as antimetabolites for the control of sugarcane whitegrubs
Authors: Allsopp P. G. , McGhie T. K. 
Published: March 2011

AbstractSnowdrop and wheatgerm lectins were found to be insecticidal and growth inhibiting dietary proteins for larvae of the sugarcane whitegrub Antitrogus parvulus. At concentrations as low as 0.5 mg of snowdrop lectin per gram of semi‐artificial diet, growth was inhibited by 21 days of feeding and significant mortality was apparent by 28 days. Wheatgerm lectin was active at similar concentrations, although expression of the effects was slower. Avidin was found to be a growth inhibiting dietary protein for larvae of Antitrogus consanguineus. At levels as low as 0.01 mg g–1 of diet, growth was inhibited by 28 days of feeding. Avidin caused no significant mortality after 35 days of feeding. Snowdrop and wheatgerm lectins and avidin are insect growth‐inhibiting proteins whose genes potentially could be manipulated into sugarcane and improve host‐plant resistance to whitegrubs.
Effects of diet on longevity and fecundity of the spined stilt bug, Jalysus wickhami
Authors: Jackson D. Michael , Kester Karen M. 
Published: March 2011

AbstractWe evaluated the suitability of selected food items for the adult spined stilt bug, Jalysus wickhami Van Duzee (Hemiptera: Berytidae), by providing one of seven diet treatments: (1) prepupae of the parasitoid, Cotesia congregata (Say) (Hymenoptera: Braconidae), on a leaf of tobacco (Nicotiana tabacum L., ‘NC 2326’) (Solanaceae); (2) C. congregata prepupae alone (i.e., no tobacco leaf); (3) eggs of the parasitoid's host, Manduca sexta (L.) (Lepidoptera: Sphingidae), on a tobacco leaf; (4) M. sexta eggs alone; (5) tobacco aphids, Myzus nicotianae Blackman (Homoptera: Aphididae), on a tobacco leaf; (6) a tobacco leaf alone; and (7) no prey and no tobacco. A tobacco leaf was necessary for the long‐term survival of stilt bugs, but prey source did not affect longevity. Regardless of the prey type, stilt bugs with access to a tobacco leaf lived 21–23 days, while stilt bugs without access to tobacco lived less than 12 days. Animal prey provided a protein source required for egg deposition in J. wickhami, and prey species differed in their relative nutritive values. Female stilt bugs that fed on M. sexta eggs or on C. congregata prepupae were significantly more fecund (102 and 106 nymphs per female, respectively) than females that fed on tobacco aphids (24 nymphs per female). Results suggest that stilt bugs may feed on tobacco aphids and C. congregata prepupae when other prey are unavailable.
Variation between laboratory populations of Encarsia formosa in their parasitization behavior on the host Bemisia tabaci
Authors: Henter Heather J. , Brasch Klara , VAN Lenteren Joop C. 
Published: March 2011

AbstractWe tested the hypothesis that two populations of the parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) differed in their behavioral interactions with the whitefly host Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). The two wasp populations were studied because previous work suggested large differences between the populations in performance on this host. In this study the populations differed behaviorally in both the number of hosts encountered and their reactions to hosts once encountered. The population reared for many years on Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) that previously performed more poorly on B. tabaci had a higher host encounter rate but rejected hosts more frequently. The population reared for a number of years on B. tabaci encountered fewer hosts but accepted a higher percentage of hosts for oviposition. The number of parasitized hosts did not differ between the two populations, however. These data demonstrate that there are heritable differences between these two populations of asexual wasps in host‐associated behavioral traits. These behavioral differences in host acceptance do not explain performance differences seen in the earlier study, however, possibly due to different conditions between the two experiments.
Field trapping of Metamasius hemipterus with synthetic aggregation pheromone
Authors: Ramirez‐Lucas Pamela , Rochat Didier , Zagatti Pierre 
Published: March 2011

AbstractThe five synthetic pheromone components of the West Indian sugarcane borer (WISB), Metamasius hemipterus (L.) (Coleoptera, Curculionidae) were tested in the field. The combination of sugarcane (SC) and the major pheromone compound, 4‐methyl‐5‐nonanol (1) was attractive. However, the addition of 2‐methyl‐4‐heptanol (2) or 2‐methyl‐4‐octanol (3) was required to reach high catch levels while 5‐nonanol (4) or 3‐hydroxy‐4‐methyl‐5‐nonanone (5) did not enhance WISB attraction. The redundancy phenomenon, here reported for the first time in rhynchophorinous species, was observed between compounds 2 and 3. SC + 1 + 3 was more attractive than living male baits, however, the sex‐ratio of the catches was equivalent between both treatments. The sex‐ratio of catches was affected by the qualitative composition of the pheromone formulation. Compound 3 had a sexual role, attracting more females while 5 seemed to play an aggregation role, luring both sexes in the same proportion.