Essential Oil Trunk Injection Into Orchard Trees: Consequences on the Performance and Preference of Hemipteran Pests.

peer reviewedApples and pears are among the most widely cultivated fruit species in the world. Pesticides are commonly applied using ground sprayers in conventional orchards; however, most of it will not reach the target plant, increasing the contamination of nontarget organisms such as natural predators, pollinators, and decomposers. Trunk injection is an alternative method of pesticide application that could reduce risks to beneficials and workers. Essential oils represent a 'green' alternative to pesticides due to their reported insecticidal, antimicrobial, antiviral, nematicidal, and antifungal properties. The aim of this study was, therefore, to evaluate the impact that the injection of a cinnamon essential oil solution into the trunk of apple and pear trees could have on their respective pests, Dysaphis plantaginea and Cacopsylla pyri, respectively. The feeding behavior (preference), the life history traits (performance), and the timing of this effect were measured. The injection of an essential oil emulsion in trees impacted hemipteran host-plant colonization, as for both species a modification of their preference and of their performance was observed. The feeding behavior of D. plantaginea was altered as a significantly lower proportion of aphids ingested phloem sap on injected trees, suggesting that the aphids starved to death. On the contrary, the feeding behavior of the psyllids was little changed compared to the control condition, implying that the observed mortality was due to intoxication. The results presented here could theoretically be used to control these two orchard hemipteran pests, although the effectiveness in real conditions still has to be demonstrated

Disrupting the feeding behavior of Hemiptera pests : a lever to promote biological protection in orchards

La capacité à s'alimenter constitue un élément clef dans le succès de colonisation des plantes hôtes par les Hémiptères phloèmophages et dans un contexte agronomique, un potentiel facteur explicatif de la prolifération des ravageurs dans une culture. Dans ce travail de thèse, nous souhaitons donc évaluer si l'efficacité de différentes méthodes de contrôle des Hémiptères phloèmophages de vergers (Dysaphis plantaginea et Cacopsylla pyri), et plus particulièrement (1) de l'utilisation d'huiles essentielles, (2) du recours à des biopesticides et (3) de l'utilisation de plantes résistantes, peut être expliquée par les modifications du comportement alimentaire et plus globalement, par des modifications en termes de préférence et de performance du ravageur. Pour certaines de ces méthodes de contrôle nous avons aussi étudié leurs effets sur le troisième niveau trophique, et plus particulièrement les parasitoïdes, afin d'évaluer si elles pouvaient impacter la régulation des Hémiptères phloèmophages par les ennemis naturels. Le premier levier impliquant l'utilisation d'huiles essentielles a mis en avant des effets contrastés sur la préférence (orientation, comportement alimentaire) et la performance des insectes suivant le mode d'application (par diffusion dans l'air ou par injection dans le tronc) et aussi suivant l'insecte ciblé (D. plantaginea ou C. pyri). L'objectif lié au second levier était de caractériser les effets létaux et sublétaux de biopesticides bactériens (lipopeptides) sur deux espèces de pucerons (D. plantaginea et Aphis fabae) et à étudier ces effets sur le troisième niveau trophique. Les résultats ont révélé que les pucerons D. plantaginea ayant survécu à l'exposition des lipopeptides les plus aphicides (Surfactines) avaient une durée d'ingestion de sève plus importante que les pucerons non exposés, tandis que l'inverse était observé pour les pucerons A. fabae. Cependant, le comportement de sélection de l'hôte par les femelles parasitoïdes Aphidius matricariae n'a pas été impacté suite à l'exposition des pucerons A. fabae. Enfin, concernant le troisième levier il s'agissait d'étudier les effets de la résistance des pommiers sur la préférence et la performance de D. plantaginea en s'intéressant à Malus domestica (comparaison de variétés) et à l'espèces sauvage Malus sylvestris, contributrice de la domestication du pommier (comparaison de populations). Dans ce contexte de résistance des plantes, nous avons voulu comprendre dans quelle mesure le comportement alimentaire de D. plantaginea pouvait être un élément explicatif des effets bottom-up du pommier domestique sur les parasitoïdes. Nous avons aussi émis l'hypothèse qu'il existait un lien entre la structuration génétique des pommiers sauvages et le comportement alimentaire de D. plantaginea. Les résultats ont révélé que la résistance des pommiers domestiques et sauvages a eu peu d'effet sur la performance des pucerons D. plantaginea, bien qu'elle ait affecté leur comportement alimentaire. Tandis que le comportement alimentaire semblait en effet constituer un facteur explicatif des effets bottom-up des variétés de pommier domestique M. domestica sur les parasitoïdes Ephedrus cerasicola, le lien entre le comportement alimentaire de D. plantaginea et la structuration génétique des pommiers sauvages européens M. sylvestris est apparu plus faible. Ces travaux soulignent l'importance de l'étude du comportement alimentaire des Hémiptères phloèmophages pour valider ou infirmer l'efficacité de méthodes alternatives à l'utilisation de pesticides chimiques conventionnels dans le contrôle des ravageursFeeding ability is a key element in the successful colonisation of host plants by phloemophagous Hemiptera and, in an agronomical context, a potential explanatory factor of pest proliferation in a crop. In this thesis, we therefore wish to evaluate whether the effectiveness of different methods of controlling phloemophagous Hemiptera in orchards (Dysaphis plantaginea and Cacopsylla pyri), namely the use of (1) essential oils, (2) biopesticides and (3) resistant plants, can be explained by changes in feeding behaviour and, more globally, by changes in pest preference and performance. For some of these control methods we also studied their effects on the third trophic level, and more specifically on parasitoids, in order to assess whether they could impact the regulation of phloemophagous Hemiptera by natural enemies. The first lever involving the use of essential oils revealed contrasting effects on the preference (orientation, feeding behaviour) and performance of the insects depending on the mode of application (by diffusion in the air or by injection in the trunk) and also depending on the targeted insect (D. plantaginea or C. pyri). The objective related to the second lever was to characterise the lethal and sublethal effects of bacterial biopesticides (lipopeptides) on two aphid species (D. plantaginea and Aphis fabae) and to study these effects on the third trophic level. The results revealed that D. plantaginea aphids that survived exposure to the most aphicidal lipopeptides (Surfactins) had a longer duration of sap ingestion than unexposed aphids, while the reverse was observed for A. fabae aphids. However, the host selection behaviour of Aphidius matricariae female parasitoids was not impacted by the exposure of A. fabae aphids. Finally, for the third lever the purpose was to study the effects of apple resistance on the preference and performance of D. plantaginea by focusing on Malus domestica (comparison of varieties) and a contributor to apple domestication, the wild species Malus sylvestris (comparison of populations). In this context of plant resistance, we sought to understand to what extent the feeding behaviour of D. plantaginea could be an explanatory element for the bottom-up effects of domesticated apple on parasitoids. We also hypothesised there was a link between the genetic structuring of wild apple trees and the feeding behaviour of D. plantaginea. The results revealed that resistance in both domestic and wild apple trees had little effect on the performance of D. plantaginea aphids, although it did affect their feeding behaviour. While the feeding behaviour did indeed seem to be a factor explaining the bottom-up effects of M. domestica domestic apple varieties on Ephedrus cerasicola parasitoids, the link between the feeding behaviour of D. plantaginea and the genetic structuring of wild European apple trees M. sylvestris appeared weaker. This work underlines the importance of studying the feeding behaviour of phloemophagous Hemiptera to validate or invalidate the effectiveness of alternative methods to the use of conventional chemical pesticides in pest contro

La perturbation du comportement alimentaire des Hémiptères ravageurs : un levier pour favoriser la protection biologique des vergers

Feeding ability is a key element in the successful colonisation of host plants by phloemophagous Hemiptera and, in an agronomical context, a potential explanatory factor of pest proliferation in a crop. In this thesis, we therefore wish to evaluate whether the effectiveness of different methods of controlling phloemophagous Hemiptera in orchards (Dysaphis plantaginea and Cacopsylla pyri), namely the use of (1) essential oils, (2) biopesticides and (3) resistant plants, can be explained by changes in feeding behaviour and, more globally, by changes in pest preference and performance. For some of these control methods we also studied their effects on the third trophic level, and more specifically on parasitoids, in order to assess whether they could impact the regulation of phloemophagous Hemiptera by natural enemies. The first lever involving the use of essential oils revealed contrasting effects on the preference (orientation, feeding behaviour) and performance of the insects depending on the mode of application (by diffusion in the air or by injection in the trunk) and also depending on the targeted insect (D. plantaginea or C. pyri). The objective related to the second lever was to characterise the lethal and sublethal effects of bacterial biopesticides (lipopeptides) on two aphid species (D. plantaginea and Aphis fabae) and to study these effects on the third trophic level. The results revealed that D. plantaginea aphids that survived exposure to the most aphicidal lipopeptides (Surfactins) had a longer duration of sap ingestion than unexposed aphids, while the reverse was observed for A. fabae aphids. However, the host selection behaviour of Aphidius matricariae female parasitoids was not impacted by the exposure of A. fabae aphids. Finally, for the third lever the purpose was to study the effects of apple resistance on the preference and performance of D. plantaginea by focusing on Malus domestica (comparison of varieties) and a contributor to apple domestication, the wild species Malus sylvestris (comparison of populations). In this context of plant resistance, we sought to understand to what extent the feeding behaviour of D. plantaginea could be an explanatory element for the bottom-up effects of domesticated apple on parasitoids. We also hypothesised there was a link between the genetic structuring of wild apple trees and the feeding behaviour of D. plantaginea. The results revealed that resistance in both domestic and wild apple trees had little effect on the performance of D. plantaginea aphids, although it did affect their feeding behaviour. While the feeding behaviour did indeed seem to be a factor explaining the bottom-up effects of M. domestica domestic apple varieties on Ephedrus cerasicola parasitoids, the link between the feeding behaviour of D. plantaginea and the genetic structuring of wild European apple trees M. sylvestris appeared weaker. This work underlines the importance of studying the feeding behaviour of phloemophagous Hemiptera to validate or invalidate the effectiveness of alternative methods to the use of conventional chemical pesticides in pest controlLa capacité à s'alimenter constitue un élément clef dans le succès de colonisation des plantes hôtes par les Hémiptères phloèmophages et dans un contexte agronomique, un potentiel facteur explicatif de la prolifération des ravageurs dans une culture. Dans ce travail de thèse, nous souhaitons donc évaluer si l'efficacité de différentes méthodes de contrôle des Hémiptères phloèmophages de vergers (Dysaphis plantaginea et Cacopsylla pyri), et plus particulièrement (1) de l'utilisation d'huiles essentielles, (2) du recours à des biopesticides et (3) de l'utilisation de plantes résistantes, peut être expliquée par les modifications du comportement alimentaire et plus globalement, par des modifications en termes de préférence et de performance du ravageur. Pour certaines de ces méthodes de contrôle nous avons aussi étudié leurs effets sur le troisième niveau trophique, et plus particulièrement les parasitoïdes, afin d'évaluer si elles pouvaient impacter la régulation des Hémiptères phloèmophages par les ennemis naturels. Le premier levier impliquant l'utilisation d'huiles essentielles a mis en avant des effets contrastés sur la préférence (orientation, comportement alimentaire) et la performance des insectes suivant le mode d'application (par diffusion dans l'air ou par injection dans le tronc) et aussi suivant l'insecte ciblé (D. plantaginea ou C. pyri). L'objectif lié au second levier était de caractériser les effets létaux et sublétaux de biopesticides bactériens (lipopeptides) sur deux espèces de pucerons (D. plantaginea et Aphis fabae) et à étudier ces effets sur le troisième niveau trophique. Les résultats ont révélé que les pucerons D. plantaginea ayant survécu à l'exposition des lipopeptides les plus aphicides (Surfactines) avaient une durée d'ingestion de sève plus importante que les pucerons non exposés, tandis que l'inverse était observé pour les pucerons A. fabae. Cependant, le comportement de sélection de l'hôte par les femelles parasitoïdes Aphidius matricariae n'a pas été impacté suite à l'exposition des pucerons A. fabae. Enfin, concernant le troisième levier il s'agissait d'étudier les effets de la résistance des pommiers sur la préférence et la performance de D. plantaginea en s'intéressant à Malus domestica (comparaison de variétés) et à l'espèces sauvage Malus sylvestris, contributrice de la domestication du pommier (comparaison de populations). Dans ce contexte de résistance des plantes, nous avons voulu comprendre dans quelle mesure le comportement alimentaire de D. plantaginea pouvait être un élément explicatif des effets bottom-up du pommier domestique sur les parasitoïdes. Nous avons aussi émis l'hypothèse qu'il existait un lien entre la structuration génétique des pommiers sauvages et le comportement alimentaire de D. plantaginea. Les résultats ont révélé que la résistance des pommiers domestiques et sauvages a eu peu d'effet sur la performance des pucerons D. plantaginea, bien qu'elle ait affecté leur comportement alimentaire. Tandis que le comportement alimentaire semblait en effet constituer un facteur explicatif des effets bottom-up des variétés de pommier domestique M. domestica sur les parasitoïdes Ephedrus cerasicola, le lien entre le comportement alimentaire de D. plantaginea et la structuration génétique des pommiers sauvages européens M. sylvestris est apparu plus faible. Ces travaux soulignent l'importance de l'étude du comportement alimentaire des Hémiptères phloèmophages pour valider ou infirmer l'efficacité de méthodes alternatives à l'utilisation de pesticides chimiques conventionnels dans le contrôle des ravageur

Élaboration de revêtements de zircone yttriée à température ambiante par le procédé d’Aerosol Deposition Method (ADM)

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Effects of Bacillus lipopeptides on the survival and behavior of the rosy apple aphid Dysaphis plantaginea

International audienceWithin the framework of biocontrol development, several natural lipopeptides produced by Bacillus subtilis show well-documented anti-microbial properties, especially in orchards. However, the number of studies on their putative insecticidal effects remain low despite the growing interest to develop new strategies of orchards pests' control. The rosy apple aphid Dysaphis plantaginea is the major aphid pest causing great leaf damage to apple trees. In this study, we submitted young adult aphids to topical application of three different families of lipopeptides, Plipastatin (Fengycin), Mycosubtilin (Iturin), and Surfactin, either separately or as a ternary mixture. Their aphicidal effects were investigated at 1, 2.5 and 5 g/L, both at 1 h and 24 h after exposure, and their effects on aphid behavior were studied at the 2.5 g/L concentration at 24 h after exposure. When delivered alone, lipopeptides displayed contrasted effects varying from no aphicidal activity for Mycosubtilin to a mortality induced even at low concentrations by Surfactin. Surprisingly, locomotor activity of the surviving aphids was only affected by the two least lethal treatments, Mycosubtilin and the ternary mix. Their feeding behavior was only impacted by Surfactin, the most lethal treatment, that unexpectedly increased phloem sap ingestion. The results are discussed in the context of lipopeptides applicability for integrated pest management

Effects of surfactins, Bacillus lipopeptides, on the behavior of an aphid and host selection by its parasitoid

International audienceBACKGROUND Lipopeptides extracted from the Bacillus genus are emerging biopesticides, especially in protecting crops against phytopathogens. Among the three main families of lipopeptides, surfactins have been identified as having insecticidal properties against several insect orders. However, the sublethal effects of these promising biopesticides on insect pests and their natural enemies remain largely unknown. The aim of this study was to evaluate the effects of surfactins topically applied on black bean aphid Aphis fabae mortality. First, the effects of surfactins on aphid mortality were determined by delivering increasing concentrations to adults and nymphs. Second, the sublethal effects of surfactins on locomotor activity and feeding behavior of surviving aphids were evaluated using the electropenetrography method. Finally, the effect of host exposure to surfactins on host selection behavior by Aphidius matricariae parasitoid females was analyzed. RESULTS Four surfactins concentrations were studied (0.5, 1, 2.5 and 5 g L-1). There was concentration-dependent mortality in response to surfactins at 24 h after treatment. Surfactins impacted aphid behavior when delivered at 1 g L-1 by inducing a greater locomotor activity and a reduction in feeding activity. By contrast, at the third trophic level, exposure of aphid hosts to surfactins did not affect behaviors leading to host recognition and acceptance by parasitoid females. CONCLUSION This study highlighted the consequences of aphid exposure to surfactins in the context of bottom-up regulation. Although surfactins could directly impact aphid behavior, they had no apparent consequences on the host selection behavior exhibited by parasitoid wasps

Genetic structure of Malus sylvestris and potential link with preference/performance by the rosy apple aphid pest Dysaphis plantaginea

The European crabapple Malus sylvestris, a crop wild relative of Malus domestica, is a major contributor to the cultivated apple genome and represents a potential source of interesting alleles or genes, particularly pest resistance traits. An original approach was used to explore the trophic interaction between M. sylvestris populations and its pest, the rosy apple aphid (Dysaphis plantaginea). Using 13 microsatellite markers, population genetic structure and level of crop-to-wild introgressions were inferred between M. sylvestris seedlings from three sites in Europe (Denmark, France, Romania), and M. domestica seedlings. Genetically characterized plants were also used to analyze aphid feeding behavior and fitness parameters. First, aphids submitted to two genetically close M. sylvestris populations (the Danish and French) exhibited similar behavioral parameters, suggesting similar patterns of resistance in these host plants. Second, the Romanian M. sylvestris population was most closely genetically related to M. domestica. Although the two plant genetic backgrounds were significantly differentiated, they showed comparable levels of sensitivity to D. plantaginea infestation. Third, aphid fitness parameters were not significantly impacted by the host plant’s genetic background. Finally, crop-to-wild introgression seemed to significantly drive resistance to D. plantaginea independent of host plant population genetic structure, with hybrids being less suitable hosts

Bacterial plant pathogens affect the locomotor behavior of the insect vector: a case study of Citrus volkameriana – Triozae erytreae – Candidatus Liberibacter asiaticus system

International audiencePlant pathogens can alter the behavior of their insect vectors as well as their survival and reproduction. The African psyllid, Trioza erytreae , is one of the vectors of Huanglongbing, a citrus disease caused mainly by “ Candidatus Liberibacter asiaticus” ( C Las). The purpose of this study was to characterize the effects of C Las on the psyllid, T. erytreae using Citrus volkamerina plants as the study system. The study focused more specifically on the C Las effects prior to and after its acquisition by the psyllid T. erytreae . Our results did not support the hypothesis that C Las effects psyllid probing behavior prior to acquisition; few differences were observed between uninfected T. erytrea feeding on C Las‐infected versus control plants. On the other hand, compared to psyllids that had completed their development on control plants, the ones that had completed their development on a C Las‐infected plant exhibited changes in their behavior (greater velocity), physiology (smaller mass) and biochemistry (lower water and lipid content). Altogether, our results confirm the existence of a marked postacquisition effect on the vector locomotor behavior and a minor preacquisition effect of C Las on the vector behavior, which can be partially explained by physiological and biochemical changes