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The capability of a non-native species to withstand adverse weather is indicative of its establishment in a novel area. An unusually cold winter of 2016/2017 that occurred in the West Carpathians of Slovakia and other regions within Europe provided an opportunity to indirectly assess survival of the invasive ambrosia beetle Xylosandrus germanus (Coleoptera: Curculionidae, Scolytinae). We compared trap captures of this species in the year preceding and succeeding the respective cold winter. Ethanol-baited traps were deployed in 24 oak dominated forest stands within the southern and central area from April to August 2016, and again from April to August 2017 to encompass the seasonal flight activity of X. germanus and to get acquainted with temporal changes in the abundance of this species in these two distant areas. Dispersing X. germanus were recorded in all surveyed stands before and after the aforementioned cold winter. Their total seasonal trap captures were lower in the southern area following low winter temperatures, but remained similar in the central area. Our results suggest that X. germanus can withstand adverse winter weather in oak dominated forests of the West Carpathians within altitudes of 171 and 450 m asl. It is likely that minimum winter temperatures will not reduce the establishment or further spread of this successful invader in forests in Central Europe.

Coniferous forests in Europe have a considerable number of pests that attack trees of all ages from youngest up to oldest ones. One of them is the large pine weevil Hylobius abietis. This species is widespread in Europe and occurs from warm southern areas (Spain) up to northern countries (Sweden, Finland). Larvae of this species do not cause damage, they help in the decomposition process of stumps and roots. Adults are harmful as they consume bark of young coniferous seedlings, above all of spruce and pine. One adult can consume on average 75 mm2 of bark per day. Individuals can live up to 4 years, and during their lives they can damage and kill several tens of coniferous seedlings. Traditional chemical protection of seedlings against this pest is and will gradually be more and more restricted or forbidden. In this review, we describe this method as well as all other alternative methods including biological protection. We estimate that H. abietis causes annual damages in Europe of almost 120 million € and damages several tens of thousands of hectares of young forest stands.

The gypsy moth is one of the most serious pests in forests and fruit tree plantations over prevailing parts of the Northern Hemisphere. This work is based on a literature review, and presents history of gypsy moth Lymantria dispar L., observed in Slovak forests within the period 1945–2020. The life cycle, hosts, natural enemies, population dynamics of pests, impact of outbreaks on forests and different management methods used in the past are discussed. Since 1945, there were nine gypsy moth outbreaks in Slovakia. Between 1945 and 2020, a total of 155,034 ha of deciduous forests were touched with varying intensity, representing an average annual damage of 2,040 ha. The strongest outbreak culminated in 2004. Totally 51,479 ha were attacked in the period of 2000–2008. We have found outbreak periods that repeat with frequency of 7.8 ±2.2 years and the average outbreak phase lasts 3.1 ±1.1 years. The period between two subsequent outbreaks seems to be more or less constant and duration of the outbreak phase seems to be gradually shortened during the study period. Several factors influencing the gypsy moth population dynamics in Slovakia are discussed. The role of biological control by using entomopathogenic fungus Entomophaga maimaiga is described.

Global climate change also influences the forest damaging agents occurrence and thus a forest health. Forest trees that are damaged by agents are in managed forests processed by salvage felling. The amount of an annual salvage felling represents the occurrence of a damaging agents occurrence in a certain year. In 2015, the area of forests in Slovakia reached 2.014 mil. ha. Within the 20 years (from 1998 to 2017), the total felling reached 162.52 mil. m3, out of this 47.99 % were ascribed to a salvage felling. Abiotic agents were the most damaging agents (42.28 mil. m3 of damaged wood), out of it a wind was the most important one. Biotic damaging agents were the second important group (32.165 mil. m3), whereas bark beetles on spruce were the most important. The third group and the less damaging one was anthropogenic agents group (3.555 mil. m3) with an air pollution as the most important damaging agent. There was no statistically significant difference in the volume of processed trees within salvage felling caused by abiotic and biotic damaging agents. However, these two groups caused significantly higher damages than the third group of anthropogenic damaging agents. There were two major wind damages, Alžbeta in 2004 and Žofia in 2014 with damaged wood 5.3 mil. m3 and 5.2 mil. m3, respectively. They occurred in southern, central and northern part of Slovakia. As damaged wood was not processed from strict nature conservation areas, the secondary damaging agents, mostly Ips typographus on Norway spruce reproduced as much that after some years it cumulatively reached or even exceeded damages from those two major windthrows episodes.

A warmer climate may potentially have a strong effect on the health status of European oak forests by weakening oak trees and facilitating mass reproduction of wood boring insects. We did a laboratory experiment in Slovakia to study the response of major pest beetles of oak and their parasitoids to different temperature regimes as background for predicting climatic effects and improving management tools of European oak forests. With higher temperatures the most important oak pest Scolytus intricatus emerged much earlier, which indicate that completion of a second generation and increased damage further north in European oak forests may be possible. Lower temperatures gave longer larval galleries and more offspring per parents but still lower beetle production due to semivoltine life cycle. For buprestids and longhorn beetles warmer temperatures resulted in more emerging offspring and a shift towards earlier emergence in the same season, but no emergence in the first season indicated that a change to univoltine populations is not likely. Reduced development success of parasitoids at the highest temperatures (25/30 °C) indicates a loss of population regulation for pest beetle populations. A warmer climate may lead to invasion of other population-regulating parasitoids, but also new serious pest may invade. With expected temperature increases it is recommended to use trap trees both in April and in June, and trap trees should be removed within 2 months instead 1 year as described in the current standard.

Background and purposeThe zigzag elm sawfly, Aproceros leucopoda (Hymenoptera), originating from Asia is being considered as one of the major pests of elm trees (Ulmus spp.) within Europe where it was first recorded in 2003. Recent investigations document the fast spread of this invasive species in many European countries. In Slovakia, A. leucopoda was first recorded in 2009 but its occurrence here has not been reported since 2009. Herein, we summarize the data from the two consecutive years about the current distribution of A. leucopoda and its hosts in Slovakia, Central Europe, focusing on infestation of elm trees by this successful invader in different altitudes.Material and methodsIn 2014 and 2015 the investigations of A. leucopoda were conducted at 101 different plots across the country. At each plot, characteristic symptoms of leaf damage, occurrence of larvae, cocoons or adults were recorded along with the geographical coordinates and the altitude, and the host trees of A. leucopoda were identified at the species level. The distribution map of A. leucopoda was drawn using the field data. The infestation of elm trees along the altitudinal gradient was analyzed with Kruskal-Wallis non-parametric analysis of variance followed by post-hoc Dunn's test for multiple comparisons.Results and conclusionsThe zigzag elm sawfly A. leucopoda was observed at 31 plots (30.7%, n = 101). In elm trees examined, generally, a low level of infestation by this pest was observed. A. leucopoda was found at plots between 107 and 701 m a.s.l. The result show that the infestation level of elm trees was decreasing with increasing altitude. Although we had only a small sample of data, we assume that the altitude has a significant effect on distribution of this pest. The field elm (Ulmus minor Mill.) was the most frequently utilized host. Data collected document the establishment of this successful invader in Slovakia.

1 Ips amitinus arrived in Northern Europe at the beginning of 1900s, although its recent expansions to the northernmost conifers have been rapid. 2 Analyses of recent records, MaxEnt models and regional population size estimates are used to discuss its peculiar range shifts and potential as a forest pest in Northern Europe. 3 Ips amitinus was probably absent in northern glacial refugia for Norway spruce in the Russian plain and northward expansions from its glacial refugia in the Central European mountains may have been slowed down by: (i) ecological barriers of post-glacial dry plains and bogs in Central Europe; (ii) heavy utilization of conifers; and (iii) Allee effects as a result of fragmented forests and an unfavourable climate for a cold-adapted species in the continental lowlands. 4 MaxEnt models predict that I. amitinus may become widespread in the Northern European forests, whereas its populations in the southernmost mountain ranges of Europe may decline in the future. 5 The population levels of I. amitinus in recently invaded northern areas are still lower than those in core areas of Central Europe, although the population development in Central Europe indicates that future bark beetle outbreak periods may boost the I. amitinus populations in Northern Europe as well.

The purpose of this study is to increase the basic understanding of outbreak dynamics in order to improve the management of bark beetle outbreaks. The spruce bark beetle Ips typographus is a major disturbance agent of European forests and is the continent’s most economically and environmentally damaging bark beetle. Outbreaks of the spruce bark beetle are often triggered by large windfall episodes, and we have utilized a unique opportunity to study a Slovakian outbreak where little salvage logging was performed in some areas after a 2.5 million m3 storm-felling in 2004. Our analyses focused on the first five years after the windfall, and we used a combination of empirical data and simulation models to understand the spatial patterns of beetle-killed forest patches developing during the outbreak. The univoltine beetle population used an increasing proportion of the windfelled trees during the two first seasons after the storm, but from the third season onwards our comparisons of inter-patch distance distributions indicated a transition from beetle production largely in windfall areas to a self-sustaining outbreak with infestation patches developing independently of the windthrows. The size of new infestation patches formed after this transition was modeled as a function of beetle pressure, estimated by the proportion of a circle area surrounding new patches that was covered by infestation patches the previous year. Our model results of patch size distribution did not correspond well with the empirical data if patch formation was modeled as a pure dispersal–diffusion process. However, beetle aggregation on individual trees appears to be important for patch development, since good correspondence with empirical data was found when beetle aggregation was incorporated in the modeled dispersal process. The strength of correspondence between the beetle aggregation model and the empirical data varied with the density of aggregation trees in the modeled landscape, and reached a maximum of 83% for a density of three aggregation trees per infestation patch. Our results suggest that efficient removal of windfelled trees up until the start of the second summer after a major windfall is important to avoid a transition into a patch-driven bark beetle outbreak that is very difficult to manage. Our results also indicate that the outcome of a patch-driven outbreak is difficult to predict, since the development of new infestation patches is not a simple function of beetle pressure but is also affected by beetle behavior and local forest conditions.

Gypsy moth, Lymantria dispar L., is one of the most important pests of deciduous trees in Europe. In regular cycles, it causes large-scale defoliation mostly of oak, Quercus spp., forests. Government authorities in the most infested countries in Europe conduct large-scale applications of pesticides against gypsy moth. In 1999, a new natural enemy, the entomopathogenic fungus Entomophaga maimaiga, was successfully introduced into a gypsy moth population in Bulgaria. Recent investigations suggest that now E. maimaiga is quickly spreading in Europe. Herein, past studies are reviewed regarding this fungus with special emphasis on its potential for becoming an important factor regulating gypsy moth populations in Europe, focusing on the host's population dynamics in relation to the fungus, the influence of environmental conditions on fungal activity, the influence of E. maimaiga on the native entomofauna, including other gypsy moth natural enemies, and spread of the fungus. Based on this analysis, the potential of E. maimaiga for providing control in European gypsy moth populations is estimated.

Salvage felling is one of the indicators of the forest health quality and stability. Most of the European Union countries monitor forest harmful agents, which account for salvage felling, in order to see trends or functionality between factors and to be able to predict their development. The systematic evidence of forest harmful agents and volume of salvage felling in Slovakia started at the Forest Research Institute in Zvolen in 1960. The paper focuses on the occurrence of the most relevant harmful agents and volume of salvage felling in the Slovak forests over the last decade. Within the 10 years period (2004–2013) salvage felling in Slovakia reached 42.31 mil. m3 of wood, which was 53.2% of the total felling. Wind and European spruce bark beetle Ips typographus damaged 78.4% of salvage wood, i.e. they were the most important pest agents. Norway spruce (Picea abies) was the most frequently damaged tree species that represented the amount of 35.6 mil. m3 of wood (81.2% of total volume of salvage felling). As Norway spruce grows mostly in mountains, these regions of Central and Northern Slovakia were most affected. At the damaged localities new forests were prevailingly established with regard to suitable ecological conditions for trees, climate change scenarios and if possible, natural regeneration has been preferred. These approaches in forest stand regeneration together with silvicultural and control measures are assumed to gradually decrease the amount of salvage felling over long term perspective.

In the period from 1992 to 2013, more than 3.8 million m3 of spruce wood from an area of 55 thousand ha of forests in the Kysuce region (Western Carpathians) was affected by bark beetles. This region has had the highest volume of salvage fellings in Slovakia. While before 1991, bark-beetle outbreak usually occurred after snow and wind disturbances, since 1992 they have occurred in the years with extremely warm and dry growing seasons and the years following them. These years were also characterised by high volumes of wood affected by honey fungus (Armillaria spp.), which only rarely took part in the calamities before 1992. Extreme deterioration of the situation occurred after 2003. In fragmented and sparse stands, the volume of wood damaged by wind increased. Artificial origin of spruce stands, their high occurrence, high age and even-agedness are likely pre-disposing factors of spruce forest decline. Bark beetles have become the most important factor of spruce decline. The most important factors driving the bark beetle attack on forest stands in the period 1973–2013 were the amount of unprocessed wood in the previous year; the amount of wood affected by honey fungus, precipitation total, and average temperature in the current growing season. Another important factor that complicated the situation was also the inferior quality of forest management.

The attractiveness of ultra high release ethanol lures to ambrosia beetles in Slovakian oak forests was tested from 2010 to 2012. A total of 24,705 specimens were captured during this three year period with Xyleborinus saxesenii (Ratzeburg, 1837) representing 49.28% (12,174 specimens) of the total. Other dominant species captured in the traps were Anisandrus dispar (F., 1792) (27.84%), Xyleborus monographus (F., 1792) (9.72%) and Trypodendron signatum (F., 1792) (6.04%). During this experiment, Xylosandrus germanus (Blandford, 1894) was detected for the first time in Slovakia with an increase in capture each year (19, 40 and 77 specimens, respectively). Flight period for ambrosia beetles in Slovakia occurs from the beginning of April through the end of September. This is the first time that ethanol baited traps were deployed in Slovakian oak forests and the lures were an effective tool for monitoring native and non-native ambrosia beetles.

The entomopathogenic fungus Entomophaga maimaiga was found for the first time in Slovakia in 2013. Late instar larvae of gypsy moth, Lymantria dispar, from two sites with different population densities were dissected to evaluate the presence of pathogens. The presence of conidia and resting spores of E. maimaiga in gypsy moth cadavers was confirmed from both sites.

In the spruce stand situated in Central Slovakia, a manipulation experiment was performed aimed at attracting spruce bark beetle (Ips typographus) to living and healthy spruce trees using pheromone dispensers. The goal of the experiment was to show that the galleries of the Ips typographus in the irrigated spruce trees differed in the parameters from the galleries in drought-stressed trees. Significant differences were revealed mainly in those gallery parameters that occur after the excavation of a nuptial chamber, or after the mating of parental beetles. The revealed differences prove that drought in combination with extreme temperatures significantly reduces defence reactions of spruce against the attack of Ips typographus. Water deficit together with high temperatures significantly postpone and retard the activation of defence reactions of spruce on one side, and accelerates the regeneration and the development of Ips typographus on the other side.

Les invasions biologiques d'insectes, de plantes et de champignons nuisibles causent souvent des perturbations considerables dans les ecosystemes forestiers ainsi que d'importants impacts socioeconomiques. L'Europe Centrale agit comme un 'pont' entre l'Europe occidentale et orientale a la fois ecologiquement et en tant que point de passage pour les personnes. L'activite humaine, dont le mouvement de biens materiels, augmente le risque d'invasions. Certaines especes introduites dans le passe se sont etablies, devenant communes et causant de serieux problemes (tels que Dreyfusia nordmannianae or Hyphantria cunea). La situation, l'importance et la repartition spatiale en Slovaquie de sept organismes nuisibles differents recemment introduits dans les ecosystemes forestiers slovaques (Cameraria ohridella, Coleotechnites piceaella, Cryphonectria parasitica, Dothistroma septospora, Ips duplicatus, Parectopa robiniella, Phyllonorycter robiniellus) ainsi que deux autres qui ne sont pas encore signales en Slovaquie (Anoplophora glabripennis, Phytophthora spp.) sont discutees.

Research was carried out in High Tatra and Low Tatra Mountains in 2009. It was aimed to compare the efficiency of two types of pheromone traps (Lindgren funnel trap and Theysohn trap), two types of lures (Ipslure and Pheroprax A) to control the spruce bark beetle (Ips typographus), characterize flight activity pattern of I. typographus and identify bark beetle species caught in traps. Altogether 40 traps were set up for bark beetles (16 traps in Low Tatra Mountains and 24 traps in High Tatra Mountains). Lindgren funnel traps yielded higher catches of I. typographus (by 18.2% on average) than Theysohn traps, although this was not statistically significant (p > 0.05). The traps baited with Pheroprax A caught a total of 3,833 individuals of I. typographus per trap, those baited with Ipslure 1,587 individuals per trap. In this particular case, the difference in the bark beetle catches between the two lures was statistically significant (p < 0.05). The flight pattern of I. typographus in both mountain areas was similar. It showed great decrease in abundance of flying individuals of I. typographus as a result of low temperatures in the middle of June. Flight patterns of the bark beetle in the two mountain areas were similar to those documented from other sites monitored in Slovakia over the growing season 2009. Altogether 25 bark beetle species (22 species in High Tatra Mts., 18 species in Low Tatra Mts.) and 1,066,494 individuals were caught. I. typographus was the dominant scolytid species in traps (over one million adults caught). Other important (abundant) bark beetles included Pityogenes chalcographus (15,914 adults), Xyloterus lineatus (2,008 adults), Dryocoetes autographus (308 adults), Hylastes cunicularius (421 adults), Hylurgops palliatus (227 adults), Orthotomicus laricis (77 adults), Crypturgus cinereus (76 adults), Polygraphus poligraphus (45 adults), followed by other less abundant and less important bark beetle species.