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Bark beetles (Curculionidae: Scolytinae) represent an important insect group including many significant pest species, but in some cases, the distribution and ecology of many bark beetles are still not well known. Maple bark beetle Scolytus koenigi Schyverew, 1890 is one of the mentioned group of species. The following study presents i) the first data of the occurrence of S. koenigi in Bohemia, ii) the first data of the species occurrence in an urban environment (large cities – Prague and Brno), iii) the distribution of the species in the Czech Republic since its first record (in 2013), and iv) new data about the bionomy of the species (i.e. a new host tree – Acer pseudoplatanus L. and refinement of the colonized substrate range diameter).

The teak bee‐hole borer (Xyleutes ceramica (Walker, 1865)) is widespread in northern Thailand and is considered the most serious pest of teak (Tectona grandis) in the country. The present study investigated the factors affecting the infestation of teak trees by this species in three plantations in northern Thailand at different spatial scales, including the tree, plot and stand levels. At each plantation, 48 plots evenly distributed in three different young stands (1–10 years), three medium‐aged stands (11–20 years) and six old stands (exceeding 20 years) were sampled. At the plots, the number of current entrance holes of X. ceramica per teak tree was counted, and the characteristics of the trees and stands were assessed. A total of 1952 teak trees were sampled, 22.7% of which were infested by X. ceramica. According to our results, infestation was much more strongly affected by stand characteristics than by the characteristics of individual trees. Above all, understorey cover exhibited substantial effect with the infestation level being strongly limited in stands with dense understories. Additionally, young and medium‐aged stands on better quality sites were found to be the most susceptible to infestation, and well‐growing and/or damaged trees were preferred by the pest species. In conclusion, major recommendations for suppressing damage caused by X. ceramica include (a) promoting and maintaining the understorey above 30% cover, (b) planting mixed stands of commercial forest trees and (c) intensively monitoring the pest in young and medium‐aged stands, especially those growing at good‐ and medium‐quality sites. [ABSTRACT FROM AUTHOR]

As walnut trees (Juglans spp.) are of high economic importance, considerable attention has been given to invasive pests of these trees in Europe. In 2016, Dryocoetes himalayensis Strohmeyer, 1908, an alien bark beetle originating from the Himalayas region of India, already present in several European countries, was confirmed to have attacked walnut trees in the Czech Republic. Within the present study, we (i) surveyed the current distribution of D. himalayensis in the Czech Republic, (ii) examined D. himalayensis phenology by rearing it in trap logs, and (iii) investigated tree level habitat preferences of the species in two study stands with 180 black walnut (Juglans nigra L.) trees and 66 common walnut (Juglans regia L.) trees sampled. The present study documented the species to be relatively widespread in some warmer lowland regions of the Czech Republic (42 localities found) and to reach high abundance locally. Almost 15 thousand D. himalayensis individuals reared from the trap logs showed the species emerging throughout the whole vegetation period with a distinctive peak in June. Even though the species is able to develop in thin stems (diameter <5 cm), it is most numerous in thicker trunk bases and also preferably attacks trees of higher diameters. The species preferred common walnut trees (its native host) with decreased vitality. In contrast, black walnut trees (North American species) were attacked regardless of their vitality, but the vitality of occupied trees successively decreased. Based on our results, D. himalayensis should be assumed as a considerable pest of walnut trees (particularly black walnuts), which might become of significant importance in its European invasive range in the future, and thus substantial attention should be given to it. [ABSTRACT FROM AUTHOR]

The bark beetle Orthotomicus laricis (F.) (Coleoptera Curculionidae Scolytinae) occurs on conifers in coniferous forests and even on confers in areas with few forests at a wide range of altitudes throughout the Czech Republic. Although O. laricis is a common species, its population densities are low. The bark beetle Orthotomicus longicollis (Gyllenhal) was recorded for the first time on pines in the Czech Republic in the 1990s and in Bohemia in 2017. O. longicollis is known only from several localities in the eastern Czech Republic at 200-400 m elevation. Several weakened trees with O. longicollis infestations along the lower parts of their trunks were found in 2017. There is no evidence that either O. laricis or O. longicollis is able to kill healthy trees, and records from the Czech Republic include no data about damage caused to timber by the two species. Neither species should be considered a primary or even a secondary pest, i.e. subeconomic pest. [ABSTRACT FROM AUTHOR]

Stem girdling is the process of completely removing a strip of cork and phloem tissue. Phloem is the living tissue which serves as the main long-distance pathway for transporting carbohydrates produced during photosynthesis to all parts of the plant where needed, from source leaves to sinks. Stem girdling has been used to study several functional aspects of phloem and their direct impacts on tree growth. Although both photosynthesis and transpiration processes take place in needles, no studies exist which investigate the effect of source-sink disturbance on needle structure. In this study, we evaluated changes in needle morphology and anatomy in current-year Scots pine needles 227 and 411 days after girdling (DAG). Although the studied needle parameters recorded 227 DAG were from 2 to 20% higher than the same parameters in control needles, the differences were not significant. On the other hand, needles 411 DAG were thinner, with decreased cross-sectional areas, phloem areas, vascular cylinder areas, needle dry mass, needle density, and needle flatness when compared to control needles. Marked variations in needle growth were observed 411 DAG, with a smaller number of correlations among almost all studied needle parameters in needles 411 DAG when compared to control needles or needles 227 DAG. Structural development determining needle flatness, needle density, and leaf mass per area (LMA) appeared to have driving factors that were independent of the other studied needle parameters, as correlations with other parameters were not significant in any treatment. The changes in overall needle structure observed after long-term stem girdling provide new insights into the processes that occur as a result of source-sink disturbances. This type of data could be helpful, for example, in studies specifically focused on phloem transport, tree carbon relationships, or investigations modeling gas exchange. Our study might also support gene expression studies, which could provide further knowledge about the regulatory mechanisms that determine needle size and structural form. [ABSTRACT FROM AUTHOR]

Logging residues form a substantial portion of the dead wood in managed forests, and logging residues can facilitate bark beetle multiplication and outbreaks. For these reasons, it is highly advisable to find a way of reducing the risk of bark beetle outbreaks without extensive removal of logging residues, which is inconsistent with nature conservation., The coverage of Pityogenes chalcographus (L.) galleries and the presence of other bark beetle species on 3520 fragments of logging residues of the Scots pine ( Pinus sylvestris L.) that originated over different months from 2004 to 2008 were examined in 135 stands in four study areas of the Czech Republic., Pityogenes chalcographus was the most abundant species., The month of felling had a significant effect on the coverage of P. chalcographus galleries on logging residues., Concentrating felling in August and September (and possibly October) can minimize the risk of P. chalcographus multiplication and outbreaks. [ABSTRACT FROM AUTHOR]