Non-target Bark Beetles in Ips duplicatus (Sahlberg) Pheromone Traps Baited with Host Volatiles

Response of several non-target bark beetles (Coleoptera: Curculionidae, Scolytinae) to different combinations of the northern spruce bark beetles synthetic pheromone with the monoterpenes (-)-alpha-pinene and (+)-limonene has been studied in choice experiments in the field with flight barrier traps. The experiments were organized in four Norway spruce stands (40-50 years old) outside its natural area, in the north-east of Romania, where Ips duplicatus (Sahlberg) populations had reached an epidemical level. Each experiment had five treatments randomly replicated in six blocks within each experimental plot. Four non-target bark beetle species were captured together with Ips duplicatus: I. typographus (L.) (2611 beetles), Pityogenes chalcographus (L.) (184 beetles), Hylastes cunicularius Erichson (107 beetles) and Dryocoetes autographus (Ratzeburg) (24 beetles), representing 1.77%, 0.13%, 0.07% and 0.02% respectively of total captures. Beetles of I. typographus were attracted by synthetic pheromone blend of I. duplicatus and have intensified their response in the presence of (-)-alpha-pinene or a combination between (-)-alpha-pinene and (+)-limonene, but the other species have been captured in the traps accidentally. The positive response of I. typographus to the present formulation of I. duplicatus pheromone suggests the possibility to use the pheromone dispensers for both species in the same traps when mass-trapping is the main goal, but new studies should clarify the real effects of putting together pheromone dispensers of I. typographus or P. chalcographus with those of I. duplicatus

Herbivory on the pedunculate oak along an urbanization gradient in Europe : Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intraurban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that – just like in non-urban areas – plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.Agence Nationale de la Recherche, Grant/Award Number: ANR-10--LABX-45; Fondation BNP Paribas.info:eu-repo/semantics/publishedVersio

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

International audienceAim: The strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom-up (plant quality) and top-down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large-scale climatic gradients on herbivory. Location: Europe. Time period: 2018–2019. Major taxa studied: Quercus robur. Methods: We simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees. Results: Climatic factors rather than latitude per se were the best predictors of the large-scale (geographical) variation in the incidence of gall-inducers and leaf-miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf-miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall-inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage. Main conclusions: These findings help to refine our understanding of the bottom-up and top-down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees

Herbivory on the pedunculate oak along an urbanization gradient in Europe : Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.Peer reviewe

Herbivory on the pedunculate oak along an urbanization gradient in Europe: Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

AimThe strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom‐up (plant quality) and top‐down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large‐scale climatic gradients on herbivory.LocationEurope.Time period2018–2019.Major taxa studiedQuercus robur.MethodsWe simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees.ResultsClimatic factors rather than latitude per se were the best predictors of the large‐scale (geographical) variation in the incidence of gall‐inducers and leaf‐miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf‐miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall‐inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage.Main conclusionsThese findings help to refine our understanding of the bottom‐up and top‐down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees.</p

Effects of Volatile Emissions of Picea abies Fresh Debris on Ips duplicatus Response to Characteristic Synthetic Pheromone

Ips duplicatus is an important pest of Norway spruce (Picea abies) planted outside of its natural range. This species uses olfactory signals to identify the spruce trees favourable for colonisation. The knowledge of the beetles’ response to these stimuli is important for managing this pest. Therefore, the response of Ips duplicatus to a specific synthetic pheromone was investigated under some natural sources of volatile emissions characteristic of Norway spruce. The pheromone traps were installed in two types of forests: one with fresh and large Norway spruce stumps and piles of branches, releasing large amounts of host volatile substances (terpenes and alcohols) and one without such fresh material. The experiment was repeated in three pairs of sites located in plantations out of the natural range of Norway spruce. Finally it was found that Ips duplicatus beetles, regardless of sex, have been concentrated in areas where large amounts of fresh material were available, confirming that Ips duplicatus beetles are using both natural pheromones and specific host volatiles as olfactory stimuli in searching for breeding material

Xylosandrus germanus (Coleoptera, Curculionidae, Scolytinae) – un potenţial dăunător al pădurilor, livezilor şi viilor din România [Xylosandrus germanus (Coleoptera, Curculionidae, Scolytinae) – a potential pest of forests, orchards and vineyards in Romania]

The black timber bark beetle, Xylosandrus germanus (Blandford 1894), is a new species for Romanian fauna and a potential invasive pest in our forests, orchards and vineyards, but there is little information about it in our scientific literature. Consequently, a short synthesis of the knowledge concerning the biology, ecology, damages, survey and control of the pest, is presented for the foresters, as well as for owners of orchards and vineyards. Preliminary data on its distribution and flight activity suggest that the pest may already be present in many zones of the country and that would have a generation per year

Xylosandrus germanus (Coleoptera, Curculionidae, Scolytinae) – un potenţial dăunător al pădurilor, livezilor şi viilor din România [Xylosandrus germanus (Coleoptera, Curculionidae, Scolytinae) – a potential pest of forests, orchards and vineyards in Romania]

The black timber bark beetle, Xylosandrus germanus (Blandford 1894), is a new species for Romanian fauna and a potential invasive pest in our forests, orchards and vineyards, but there is little information about it in our scientific literature. Consequently, a short synthesis of the knowledge concerning the biology, ecology, damages, survey and control of the pest, is presented for the foresters, as well as for owners of orchards and vineyards. Preliminary data on its distribution and flight activity suggest that the pest may already be present in many zones of the country and that would have a generation per year