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Red wood ants (RWA), belonging to the Formica rufa species group, play a crucial and fascinating role in Central Europe’s forest ecosystems. They have a high variety of effects, which they exert around their nests. Their generalist feeding on prey in the canopies of trees lowers the frequency of defoliator outbreaks, as well as increases local biodiversity. Nearly half of their diverse diet is insects, including species considered harmful by foresters. They also have a mutualistic relation with honeydew-producing aphids and planthoppers, which connection has unclear effects on the forests. The habit of RWAs building nests could also positively influence soil composition, due to its structure and high amount of organic matter, which could potentially benefit tree growth. RWAs are also known to enhance the species richness of forests by supporting various myrmecophilous species associated with them. In this study, we review the role of RWAs in forest protection, drawing on the literature focusing on Hungary and Central Europe.

The North American gall mite Aceria fraxiniflora was first recorded in Europe in southeast Hungary in 2017. Since then, it has shown a remarkably rapid spread on its host, the also North American green ash (Fraxinus pennsylvanica). By the beginning of 2023 it has been recorded in eight Central-Eastern European countries. In 2022 it was recorded on the other North American ash (Fraxinus Americana) in Zagreb (Croatia) and in Szarvas Arboretum (SE Hungary). Possible reasons and outcomes of this spread are discussed.

The North American oak lace bug (OLB, ) was first found in Europe in northern Italy in 2000, and up to 2019 it was recorded in 20 countries. Almost all Eurasian deciduous oak species are suitable hosts and the species can also feed on many other woody plants. At least 30 million hectares of oak forests provide suitable hosts for the OLB, meaning that the lack of suitable hosts will not restrict its further spread. Detailed studies on the long-term impact of the species are not yet available but there are many good reasons to assume that it poses multiple threats to oaks and oak ecosystems. In the long term, it may have negative effects on oak health, growth, and acorn crops. Many of other oak-associated species will likely also be negatively affected. So far, no effective and environmentally tolerable large scale control method is known for OLB.

BACKGROUND: Two jewel beetle species native to Europe, the cypress jewel beetle, Lamprodila (Palmar, Ovalisia) festiva L. (Buprestidae, Coleoptera), and the sinuate pear tree borer, Agrilus sinuatus Olivier (Buprestidae, Coleoptera), are key pests of ornamental thuja and junipers and of orchard and ornamental rosaceous trees, respectively. Although chemical control measures are available, due to the beetles’ small size, agility, and cryptic lifestyle at the larval stage, efficient tools for their detection and monitoring are missing. Consequently, by the time emerging jewel beetle adults are noticed, the trees are typically significantly damaged. METHODS: Thus, the aim of this study was to initiate the development of monitoring traps. Transparent, light green, and purple sticky sheets and multifunnel traps were compared in field experiments in Hungary. RESULTS: Light green and transparent sticky traps caught more L. festiva and A. sinuatus jewel beetles than non-sticky multifunnel traps, regardless of the larger size of the colored surface of the funnel traps. CONCLUSIONS: Although light green sticky sheets turned out to be optimal for both species, using transparent sheets can reduce catches of non-target insects. The key to the effectiveness of sticky traps, despite their reduced suitability for quantitative comparisons, may lie in the behavioral responses of the beetles to the optical features of the traps.

The North American oak lace bug ( ) was first discovered in Europe (Norhern Italy) in 2000. It started a rapid area expansion in the last decade and has been reported in 20 countries so far. Almost all European oaks are suitable hosts. On top of the host availability, abiotic factors like weather/climate may also have a decisive impact on its further spread and future outbreaks. We conducted a simple field survey within three years, at five locations to estimate the overwintering mortality of the species. Our results suggest that not even a relatively harsh winter (as 2016/2017) caused severe mortality in the overwintering populations. The average mortality of the nine year/location combinations was 30.6% (range 9.1–58.5%). Based on this, the low winter temperature is unlikely to restrict its further spread, therefore continuing area expansion can be predicted.

Both artificial and natural regeneration of oaks strongly depend on the quantity and quality of the acorn crop, which show high year-to-year variation. The volume of the acorn crop is influenced by many factors including biotic and abiotic effects. The quality (i.e., germination ability, nutrient reserves) of acorns can be decreased by carpophagous insect and fungal pathogen damage or by inadequate weather conditions. Defoliating insects (caterpillars, sawfly larva, etc.) can significantly decrease the acorn crop as well. The most important predators of the defoliators are insectivorous birds during their nesting period. However, in the oak forests of the northern Hungarian mountains, there is a shortage of natural nesting holes. The main aim of our study was to artificially increase the number of the available nesting holes by nest boxes and to maximize the number of breeding insectivorous birds and register the direct (Lepidoptera densities) and indirect (acorn crop quantity and quality) effects of their presence. We found only slight effects on Lepidoptera densities, so we failed to demonstrate a direct effect in the relatively low time frame of our study. But, we could show the indirect positive effect of increased predation on the health state of the acorn crop, resulting in higher seedling densities, which may improve the natural regeneration potential of sessile oak. This result supports the outstanding importance of natural nesting holes in broadleaved forests.

The oak lace bug (OLB) Corythucha arcuata (Say, 1832) is an invasive alien species (IAS) that potentially could have many negative impacts on European oak health. Certain measures can be applied to counteract these effects. However, these measures may not be acceptable for forest managers or other stakeholder groups, such as private forest owners, environmental NGOs or the general public. Thereby, we set out to study the perception and knowledge of foresters and other stakeholders on the health status of European oak forests affected by oak lace bug and to investigate what forest health management measures would be acceptable to these target groups. An online survey questionnaire was designed and distributed via social networks, as well as professional networks via e-mails. The survey questionnaire was completed by 2084 respondents from nine European countries: Austria, Croatia, Belgium, France, Hungary, Italy, Romania, Serbia and Slovenia. Even though only a little over 60% of respondents reported they had noticed the discolouration of oak leaves caused by OLB, almost all (93%) considered it to be a problem. As respondents come from a country where C. arcuata is widespread and established, people’s general knowledge and awareness of OLB began to increase. The survey revealed that foresters thought that the insect affected photosynthesis, acorn crop and the aesthetics of the trees, but cannot cause death of trees. However, they assume that the value of the wood would decrease (this fact is also supported by the respondents who are connected to an environmental NGO), but that OLB does not affect property value. However, forest owners claim that the value of the property can be affected and that people would avoid entering the forest. In terms of potential control methods, respondents preferred biological or mechanical measures over chemical ones. We consider this study to be a good basis for further research on the topic of perception, knowledge and attitudes related to OLB since we can expect that the IAS, such as OLB, will certainly spread to European countries that were not included in this survey.

Against the background of the phenomenon of globalisation, which has increasingly intensified in recent decades, invasive alien species (IAS) have led to biological invasions that have resulted in multiple negative effects on economies, human health, and especially on the environment. In order to control invasive alien species, preventive actions are considered the most effective methods. In this context, society can actively participate in the process of early detection and preventing the spread of these organisms, but there is a need to raise public awareness. In order for this process to take place in the most efficient way, it is necessary to initially evaluate the knowledge of the general public to IAS. Through a questionnaire that was circulated in ten European countries and had over two thousand respondents, this study aimed to investigate the level of knowledge of some stakeholders in the forestry sector regarding IAS. The results showed that a vast majority of respondents who participated in the study had heard about IAS and provided a correct definition of these organisms. Most of the respondents in this study heard for the first time about IAS from school, the Internet, or journal articles. Data analysis also showed that stakeholders in the forestry sector (foresters, forest owners, and members of environmental NGOs) were more likely than the other respondents to be aware of the impact of IAS. The results of this study offer an insight to researchers and decision makers assessing the differences of opinion regarding invasive alien species, and the necessary steps that could be adopted in the process of raising awareness in society.