Comprehensive assessments of the chemical profiles of woody cell wall components, and leaf growth, ecophysiological, vascular and nanomechanical traits for two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess contrasting tolerances toward Dutch elm disease, were made. Upon infection with Ophiostoma novo-ulmi ssp. americana × novo-ulmi, medium-molecular weight macromolecules of cellulose were degraded in both hybrids. A loss of crystalline and non-crystalline cellulose regions occurred in parallel. In 'Groeneveld' plants, syringyl-rich lignin provided far greater degree of protection from cellulose degradation, but only guaiacyl-rich lignin in 'Dodoens' plants was involved in a successful defence against the fungus. Unexpectedly, we found a very high proportion of non-significant differences between the infected and non-infected plants of 'Dodoens', including similarities in leaf growth, leaf gas exchange and leaf midrib vascular traits, as well as in the nanomechanical properties of the cell walls of tracheary elements such as modulus of elasticity, adhesion and energy dissipation. Three years after initial inoculations, except for a few traits such as leaf slenderness, relative chlorophyll content, transpiration rate and sap flow density in branches, we found no evidence of a decrease in leaf trait performances among the infected plants of 'Dodoens', despite the occasional persistence of fungal hyphae in the lumens of leaf midrib tracheary elements.

Keywords: cellulose degradation, nuclear magnetic resonance, modulus of elasticity, Ophiostoma novo-ulmi, syringyl to guaiacyl ratio in lignin, transpiration

   Information about Eulachnini species in Lithuania concerns fragmentary faunistic data, therefore, their diversity, abundancy and ecological specificity is insufficiently studied. The aim of this work was to present available information on the new to Lithuania Eulachnini aphid species detected on coniferous plants in Lithuania in 2004 - 2017, with special regard to their potential impacts on forestry. Partial COI sequences (652 bp) were used to confirm morphology-based identification of the new to Lithuania Eulachnini species and to investigate their genetic diversity and relationships with samples collected in other countries. Twenty-seven aphid species of the tribe Eulachnini were detected in 2004 – 2017 in Lithuania. Eight of them are reported from Lithuania for the first time: Cinara (Cinara) brauni, C. (C.) kochiana, C. (C.) neubergi, C. (C.) laricis, C. (C.) pectinatae, C. (C.) piceae, Eulachnus brevipilosus and E. nigricola. Five species of Eulachnini (C. (C.) piceae, C. (C.) nuda, C. (C.) piceicola, C. (C.) pinea, and C. (C.) pini) appeared to be most promising honeydew producers because of their host plants, Picea abies and Pinus sylvestris, which are the most common conifers in Lithuania. Although five species of Eulachnini were listed in the identification key of forest pests in Lithuania, none of them were of particular importance for now. Out of the recently reported species, only Cinara piceae may be a potential forest pest as it appeared to be rather common in Lithuania and it has been reported as a pest of firs in nurseries of the Czech Republic and Northern Caucasus. Most of the samples from Lithuania represented COI haplotypes which were not previously detected in other countries.

Keywords: Cinara; coniferous trees; Eulachnus; Lithuania; mitochondrial COI.

   As a white-rot basidiomycetous and wood-decaying fungus, Phlebiopsis gigantea (Fr.: Fr.) Jülich is able to degrade lignin, cellulose and hemicellulose with a complex set of extracellular enzymes. Enzyme activity of this fungus has not been sufficiently explored.

   The aim of this study was to assess the activity of laccase and peroxidases as well as the level of micromolecular compounds in P. gigantea strains, grown on pieces of Norway spruce wood (sapwood and heartwood) over 50 days of incubation under laboratory conditions. Enzymatic activity was determined using spectrophotometry. Phlebiopsis gigantea strains showed laccase (Lacc), manganese peroxidase (MnP), lignin peroxidase (LiP) and versatile peroxidase (VP) activity. Hydroxy– and methoxyphenols were released during this process as well. High levels of MnP activity (from 5.5 to 107.847 mU/μg of protein in cultures on sapwood and from 7.585 to 229.055 mU/μg of protein in cultures on heartwood) were observed in P. gigantea strains, as well as high activity of VP with manganese-oxidizing properties (from 3.36 to 61.708 mU/μg of protein on sapwood and from 1.7 to 254.479 mU/μg of protein on heartwood) compared with the other examined extracellular enzymes. Laccase and LiP activity were found to be low in all strains of P. gigantea as well as the activity of VP in terms of guaiacol-oxidizing properties (both on sapwood and heartwood samples).

Keywords: white-rot fungus, Phlebiopsis gigantea, laccase, manganese peroxidase, lignin peroxidase, versatile peroxidase, hydroxyphenols, methoxyphenols.

   The assemblages of phytoseiid mites on the leaves of Tilia cordata and T. platyphyllos planted in heterogeneous urban habitats were studied. Six phytoseiid species, namely, Euseius finlandicus, E. gallicus, Neoseiulella tiliarum, N. aceri, Paraseiulus talbii, and Typhlodromus (Typhlodromus) pyri, were found on the studied linden leaves.

   The results indicate that both T. cordata and T. platyphyllos may serve as favourable host plants for the generalists E. finlandicus and N. tiliarum in urban environments. Both generalist predatory species preferred sheltered leaf microhabitats. The first record of E. gallicus in central Europe and the consistent occurrence of other phytoseiid species on the surveyed linden trees confirm the important role of urban greenery in landscape biodiversity.

Keywords: Tilia, Acari, Phytoseiidae, Euseius gallicus, leaf microhabitat, urban greenery