1,720,982 research outputs found
Modelling the impact of GM plants and insecticides on arthropod populations of agricultural interest
No full textMatrix population models (MPM) are nowadays not widely used to simulate arthropod population dynamics with applications to risk assessment. However, an increasing body of studies are prompting the finding of optimization techniques to reduce uncertainty in matrix parameters estimation. Indeed, uncertainty in parameters estimates may lead to significant management implications. Here we present two case studies where MPM are used for assessing the potential impact of genetically modified (GM) plants on beneficial insect species (the coccinellid Adalia bipunctata) and for evaluating spider mites (the two-spotted spider mite Teranychus urticae) resurgence after insecticide application. In both studies the data obtained, consisting of population time series, were used to generate a stage-classified projection matrix. The general model used to simulate population dynamics consists of a matrix containing (i) survival probabilities (the probability of growing and moving to the next stage and the probability of surviving and remaining in the same stage), and (ii) fecundities of the population. Most of the methods utilized for estimate the parameter values of stage-classified models rely on following cohorts of identified individuals [1]. However in these studies the observed data consisted of a time-series of population vectors n(t), for t = T0, T1, ..., Tn, where individuals are not distinguished. The relationship between the observed data and the values of the matrix parameters that produced the series involves an estimation process called inverse problem. The set of parameters that minimize the residual between the collected data and the model output for the two studies presented here was estimated using the quadratic programming method [2]. The set of estimated parameters for the A. bipunctata Rhopalosiphum maidis maize tritrophic system model supports the hypothesis that GM maize does not negatively influences A. bipunctata population growth in the tritrophic system studied [3]. Otherwise, in the case of the two-spotted spider mite resurgence, some insecticides, namely etofenprox, deltamethrin and betacifluthrin, fostered a higher mite population growth than the untreated control. This was principally due to higher adult fecundity and egg fertility, clearly explained by Life Table Response Experiments, performed starting from estimated matrices, indicating a likely trophobiotic effect. A variety of inverse modelling approaches have been applied to demographic models other than quadratic programming. Bayesian approaches [4] and evolutionary algorithms, such as Genetic Algorithms [5] have also been used for inverse modelling and parameters fitting. In order to find a better model fit for the observed stage class distributions on two case studies, we would like to explore Neural Networks or more generally machine learning possibilities in finding a set of parameter values that successfully describes observed data
Toxicity and residual activity of spinetoram to neonate larvae of Grapholita molesta (Busck) and Cydia pomonella (L.) (Lepidoptera: Tortricidae): Semi-field and laboratory trials
No full textSpinetoram is a fermentation insecticide, derived from the actinomycete Saccharopolyspora spinosa. It works by disrupting the GABA-gated chloride channels and by causing persistent activation of insect nicotinic acetylcholine receptors. This study aimed to evaluate the efficacy of spinetoram for control of neonate larvae of both oriental fruit moth (OFM) Grapholita molesta (Busck) and codling moth (CM) Cydia pomonella (L.) in semi-field and laboratory trials. OFM and CM neonate larvae responded similarly to spinetoram, which showed high efficacy on both species. In semi-field experiments, regression analysis of the percentage of damaged fruits as a function of days after treatment showed a better performance of the highest spinetoram dose (10 g a.i./hl) in comparison with the maximum recommended field dose of the reference product emamectin benzoate (2.85 g a.i./hl). Surface-treated diet assays revealed LC50 values of 6.59 and 8.44 ng a.i./cm2 for neonate larvae of OFM and CM larvae, respectively. High percentages of mortality were recorded on both species after 24-h exposure to treated diet. For these reasons spinetoram could be considered a valuable tool in IPM strategies for OFM and CM control
Lethal and Sub-lethal Effects of Four Insecticides on the Aphidophagous Coccinellid Adalia bipunctata (Coleoptera: Coccinellidae)
No full textConventional insecticide assays, which measure the effects of insecticide exposure on short-term mortality, overlook important traits, including persistence of toxicity or sub-lethal effects. Therefore, such approaches are especially inadequate for prediction of the overall impact of insecticides on beneficial arthropods. In this study, the side effects of four modern insecticides (chlorantraniliprole, emamectin benzoate, spinosad, and spirotetramat) on Adalia bipunctata (L.) (Coleoptera: Coccinellidae) were evaluated under laboratory conditions by exposition on treated potted plants. In addition to investigation of acute toxicity and persistence of harmful activity in both larvae and adults of A. bipunctata, demographic parameters were evaluated, to provide a comprehensive picture of the nontarget effects of these products. Field doses of the four insecticides caused detrimental effects to A. bipunctata; but in different ways. Overall, spinosad showed the best toxicological profile among the products tested. Emamectin benzoate could be considered a low-risk insecticide, but had high persistence. Chlorantraniliprole exhibited lethal effects on early instar larvae and adults, along with a long-lasting activity, instead spirotetramat showed a low impact on larval and adult mortality and can be considered a short-lived insecticide. However, demographic analysis demonstrated that chlorantraniliprole and spirotetramat caused sub-lethal effects. Our findings highlight that sole assessment of mortality can lead to underestimation of the full impact of pesticides on nontarget insects. Demographic analysis was demonstrated to be a sensitive method for detection of the sub-lethal effects of insecticides on A. bipunctata, and this approach should be considered for evaluation of insecticide selectivity
Evaluation of the susceptibility to emamectin benzoate and lambda cyhalothrin in European populations of Cydia pomonella (L.) (Lepidoptera: Tortricidae)
Full text linkThe codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is one of the key pests of pome fruit and walnut in almost all growing regions of the world and has developed resistance to several insecticides. In this study, the susceptibilities of 15 codling moth populations to emamectin benzoate and 9 populations to lambda cyhalothrin collected in five European countries were measured by standard diet incorporation bioassays. Variation in susceptibility was observed among populations, with LC50 values ranging from 0.0017 to 0.0119 mg a.i./kg diet for emamectin benzoate and from 0.033 to 0.292 mg a.i./kg diet for lambda cyhalothrin. Our results revealed only small variations in emamectin benzoate susceptibility between populations, indicating no selection of resistance to this active ingredient. Even though a wider range of responses was detected for lambda cyhalothrin, our results also suggest that populations remain susceptible to this insecticide. Based on pooled LC95 evaluations, we propose the use of concentrations 0.02 mg a.i./kg of diet for emamectin benzoate and 0.60 mg a.i./kg of diet for lambda cyhalothrin in order to discriminate between resistant and susceptible individuals
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
(Hemiptera: Pentatomidae)
Full text linkBackgroundHalyomorpha halys, (brown marmorated stink bug, BMSB), is a high-concern invasive species causing severe damage to orchards in many countries outside its native Asian range. Management methods other than frequent sprays of broad-spectrum insecticides are needed to restore integrated pest management (IPM) practices in orchards. Chitin synthesis inhibitors are usually regarded as desirable options in IPM programs because of lower toxicity to beneficial insects and non-target organisms compared to neurotoxic insecticides. In this study, the activity of three chitin synthesis inhibitors (namely buprofezin, novaluron and triflumuron) was investigated on BMSB egg masses, third instars and adults by means of laboratory bioassays. ResultsNovaluron and to a lesser extent triflumuron were detrimental to BMSB nymphs exposed to residues on potted peach plants. Novaluron caused high mortality among early instars that emerged from sprayed egg masses. No significant differences were found between buprofezin and water control on eggs or third instars. When sprayed on BMSB adults, none of the chitin synthesis inhibitors affected survival, fecundity, or egg hatching. ConclusionGiven the activity on nymphs, but the lack of effects on adults, novaluron and triflumuron might be considered for field applications only as a tool in a wider management strategy along with other methods aimed at preventing the invasion of crops by BMSB adults. (c) 2023 Society of Chemical Industry
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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