Phytophagous larvae occurring in Central and Southeastern European oak forests as a potential host of Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) - A field study.

We evaluated the presence and impact of Entomophaga maimaiga on both target and non-target phytophagous larvae. All six study plots, with low gypsy moth population density, were situated in Central and Southeastern European oak forests and E. maimaiga had previously been reported from these plots. Totally, 45 of 4,045 (1.13%) collected non-target larvae died due to fungal infections. No non-target insect specimen was infected by E.maimaiga, although the presence of the pathogen could not be fully excluded in three cadavers. Out of 1,780L.dispar larvae collected, 15individuals (0.84%) were infected by E.maimaiga.

The ongoing range expansion of the invasive oak lace bug across Europe: current occurrence and potential distribution under climate change.

In recent years, the oak lace bug, Corythucha arcuata, has emerged as a significant threat to European oak forests. This species, native to North America, has in the last two decades rapidly extended its range in Europe, raising concerns about its potential impact on the continent's invaluable oak populations. To address this growing concern, we conducted an extensive study to assess the distribution, colonization patterns, and potential ecological niche of the oak lace bug in Europe. We gathered 1792 unique presence coordinates from 21 Eurasian countries, utilizing diverse sources such as research observations, citizen science initiatives, GBIF database, and social media reports. To delineate the realized niche and future distribution, we employed an ensemble species distribution modelling (SDM) framework. Two future greenhouse gas scenarios (RCP 4.5 and RCP 8.5) were considered across three-time intervals (2021-2040, 2061-2080, and 2081-2100) to project and evaluate the species' potential distribution in the future. Our analysis revealed that significant hotspots rich in host species occurrence for this invasive insect remain uninvaded so far, even within its suitable habitat. Furthermore, the native ranges of Turkey oak (Quercus cerris L.) and Hungarian oak (Quercus frainetto L.) species offer entirely suitable environments for the oak lace bug. In contrast, the pedunculate oak and sessile oak distribution ranges currently show only 40 % and 50 % suitability for colonization, respectively. However, our predictive models indicate a significant transformation in the habitat suitability of the oak lace bug, with suitability for these two oak species increasing by up to 90 %. This shift underlines an evolving landscape where the oak lace bug may exploit more of its available habitats than initially expected. It emphasises the pressing need for proactive measures to manage and stop its expanding presence, which may lead to a harmful impact on the oak population across the European landscape.

Comprehensive comparison of treatments for controlling the large pine weevil (Hylobius abietis) in Central Europe.

Adults of the large pine weevil (Hylobius abietis) cause serious damage to coniferous seedlings and are among the most important forest pests in Europe. Seedling protection by chemicals is gradually being restricted or banned for environmental reasons, and non-chemical alternatives are therefore needed. In this 3-year study, we compared the following five treatments for protecting Norway spruce seedlings against H. abietis in the Central European mountains where the weevil is especially abundant: alpha-cypermethrin sprays (the only chemical treatment); coating with sprayed glue (Vermifix); wax coating with C and F types (Norsk Wax); and physical protection with collars. The same block design was set up at a clear-cut site and at a nursery site to compare seedling mortality and wax quality under "wild conditions" with pests and under "ideal conditions" without pests. Repeated application of alpha-cypermethrin was the most effective and least expensive method to protect seedlings against H. abietis. Among the four non-chemical methods, repeated application of glue was the most effective. Because collars were moderately effective but not cost-effective, we do not recommend the use of collars. Wax was inexpensive and environmentally safe but protected seedlings for only 1 year; the newer F type of wax performed better than the C type of wax, and perhaps the F type can be improved. In general we found that seedlings at sites with high numbers of H. abietis require protection for at least 3 years. We conclude by providing an overview of all methods currently available for managing H. abietis in forests.

Host specificity of microsporidia pathogenic to the gypsy moth, Lymantria dispar (L.): field studies in Slovakia.

Several species of microsporidia are important chronic pathogens of Lymantria dispar in Europe but have never been recovered from North American gypsy moth populations. The major issue for their introduction into North American L. dispar populations is concern about their safety to native non-target insects. In this study, we evaluated the susceptibility of sympatric non-target Lepidoptera to two species of microsporidia, Nosema lymantriae and Vairimorpha disparis, isolated from European populations of L. dispar and applied in field plots in Slovakia. Application of ultra low volume sprays of the microsporidia maximized coverage of infective spores in a complex natural environment and, thus, exposure of non-target species to the pathogens. Of 653 non-target larvae collected from plots treated with V. disparis in 2002, 18 individual larvae representing nine species in four families were infected. These plots were monitored for two subsequent seasons and V. disparis was not recovered from non-target species. Of 2571 non-target larvae collected in N. lymantriae-treated sites, one larva was found to be infected. Both species of microsporidia, particularly N. lymantriae, appear to have a very narrow host range in the field, even when an inundative technique is used for their introduction. V. disparis infections in L. dispar exceeded 40% of recovered larvae in the treated study sites; infection rates were lower in sites sprayed with N. lymantriae. Several naturally-occurring pathogens were recorded from the non-target species. The most common pathogen, isolated from 21 species in eight families, was a microsporidium in the genus Cystosporogenes.

Quantifying horizontal transmission of Nosema lymantriae, a microsporidian pathogen of the gypsy moth, Lymantria dispar (Lep., Lymantriidae) in field cage studies.

Nosema lymantriae is a microsporidian pathogen of the gypsy moth, Lymantria dispar that has been documented to be at least partially responsible for the collapse of L. dispar outbreak populations in Europe. To quantify horizontal transmission of this pathogen under field conditions we performed caged-tree experiments that varied (1) the density of the pathogen through the introduction of laboratory-infected larvae, and (2) the total time that susceptible (test) larvae were exposed to these infected larvae. The time frame of the experiments extended from the early phase of colonization of the target tissues by the microsporidium to the onset of pathogen-induced mortality or pupation of test larvae. Upon termination of each experiment, the prevalence of infection in test larvae was evaluated. In the experiments performed over a range of pathogen densities, infection of test larvae increased with increasing density of inoculated larvae, from 14.2+/-3.5% at density of 10 inoculated per 100 larvae to 36.7+/-5.7% at 30 inoculated per 100 larvae. At higher densities, percent infection in test larvae appeared to level off (35.7+/-5.5% at 50 inoculated per 100 larvae). When larval exposure to the pathogen was varied, transmission of N. lymantriae did not occur within the first 15 d post-inoculation (dpi) (11 d post-exposure of test larvae to inoculated larvae). We found the first infected test larvae in samples taken 20dpi (16 d post-exposure). Transmission increased over time; in the cages sampled 25dpi (21 d post-exposure), Nosema prevalence in test larvae ranged from 20.6% to 39.2%.