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Semiochemical-mediated host selection by Xylosandrus spp. ambrosia beetles (Coleoptera: Curculionidae) attacking horticultural tree crops: A review of basic and applied science
No full textExotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic: Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked by X. crassiusculus and X. germanus, but the influence of stress on host selection by X. compactus is less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push-pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularly X. crassiusculus and X. germanus
Fungal pathogen and ethanol affect host selection and colonization success in ambrosia beetles
No full textTrap captures of invasive ambrosia beetles (Coleoptera: Curculionidae) as influenced by ethanol release rate
Full text linkInfestations of ambrosia beetles in the tribe Xyleborini (Coleoptera: Scolytinae) are associated with economic losses to horticultural trees due to branch die-back and tree death. Ethanol is a key attractant used for monitoring flight activity. Trapping experiments were conducted in woodlots in Ohio, USA, and Veneto, Italy, to characterize the effect of ethanol release rate on captures of Anisandrus maiche, Xyleborinus saxesenii, Xylosandrus crassiusculus and Xylosandrus germanus. In Ohio (2019, 2020 and 2021) and Italy (2021), traps were baited with centrifuge tubes that were modified to achieve ethanol release rates of 0.1-13.2 g/day. In Ohio (2022), traps were baited with varying quantities of manufactured lures to achieve release rates of 0.02-1.4 g/day. There was no consistent relationship between ethanol release rate and trap captures for the modified centrifuge tubes. In nine of sixteen analyses, traps baited with the centrifuge tubes releasing ethanol at 1.1 g/day or higher collected more A. maiche, X. saxesenii, X. crassiusculus and X. germanus than traps baited with centrifuge tubes releasing 0.1 g/day. In contrast, the manufactured lures releasing 0.1-1.4 g/day attracted more A. maiche, X. saxesenii, X. crassiusculus and X. germanus than lures releasing 0.02-0.05 g/day. This comprehensive study provides important insights into monitoring tactics for ambrosia beetles along with implications for optimizing ethanol-baited traps as part of a 'push-pull' strategy whereby repellents are used to 'push' beetles away from vulnerable trees and attractants are used to 'pull' them into annihilative traps
Simulated flood-stress and X-ray tomography unveil susceptibility of different tree taxa to ambrosia beetles
Full text linkClimate change will lead to higher frequencies of natural disasters, including flooding events. Consequently,
more severe and widespread attacks by invasive ambrosia beetles associated with stressed trees are predicted to occur. In this scenario, understanding which tree species are expected to be more susceptible, as well as which ambrosia beetle species could be expected to have the biggest impacts, represent a research priority. To this aim, potted-trees of eight tree species (four in the order Fagales and four in the order Rosales) were first exposed to flood-stress in a common garden experiment; then emerging insects were counted and logs obtained from infested trees were analyzed through X-ray tomography to evaluate host selection patterns (entry holes), colonization success (percentage of branched galleries and offspring production), and potential damage to the tree (volume of the log occupied by galleries) by native and exotic ambrosia beetle species. Four ambrosia beetle species attacked flood-stressed trees: the native Anisandrus dispar and Xyleborinus saxesenii, and the exotic Xylosandrus crassiusculus and Xylosandrus germanus. Flood-stressed Rosales species were consistently more attacked than Fagales species, with different ambrosia beetle species showing distinct preferences for certain tree species. Rosales were also generally more suitable for ambrosia beetle reproduction than Fagales, even though differences were also evident among tree species within the two orders. The exotic X. crassiusculus was the most successful species, showing higher percentage of branched galleries and higher offspring production. Our study showed a differential susceptibility of common tree species to native and exotic ambrosia beetles in a flood-stress scenario. In addition, it highlighted that X-ray tomography provides a novel method for characterizing the host selection and colonization of trees by ambrosia beetles and can be considered a reliable methodology to improve our comprehension of these mechanisms
Host plant selection and performance of ambrosia beetles in flood-stressed versus ethanol-injected trees provide implications for management strategies
Full text linkAmbrosia beetles (Curculionidae: Scolytinae and Platypodinae) are fungus-farming woodborers that can cause damage to the trees they colonize. Some of these beetles target stressed plants that emit ethanol, and management strategies have proposed using ethanol-injected trees as trap trees to monitor or divert dispersing adult females away from valuable crops. In this study, we used container-grown trees from 8 species to compare the effect of ethanol injection versus flooding on ambrosia beetle host selection and colonization success. Our aims were to understand whether ethanol injection is a suitable technique for different ambrosia beetle species and whether its effectiveness varies depending on the tree species used. In addition, we quantified the amount of ethanol in tree tissues to understand whether ethanol concentration could reflect observed differences among treatments and tree species. Our findings demonstrated that ethanol-injected trees were significantly more selected by both Xyleborinus saxesenii and Xylosandrus spp. and that significantly more adult beetles of both taxa emerged from ethanol-injected than flood-stressed trees. In addition, we showed that ethanol injection can trigger attacks by X. saxesenii and Xylosandrus spp. on a variety of deciduous tree species, nullifying the effects of the species-specific characteristics observed on flood-stressed trees, which can only partially be attributed to the amount of ethanol within the plant. This supported the idea that practitioners can potentially select any species of deciduous trees in management programs for ambrosia beetles based on ethanol-injected trees
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
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
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