The commercial interest in honeydew honey is increasing because of its higher therapeutic properties than most flower-based honeys. Marchalina hellenica Gennadius (Hemiptera: Marchalinidae) is one of the important scale insects to produce of honeydew honey and its honeydew in large quantities is collected by honeybees and used in pine honey in Turkey. The aim of this study was to survey and identify honeydew producing insects’ habitats that source of honeydew honey in pure fir forest in Bolu, spruce forests in Giresun (Black Sea re- gion), oaks forest in Kırklareli (Thracian region) and cedar forest in Antalya (Mediterranean region). In accordance with these results, we found 20 honeydew producers and among of them are Cinara cedri Mimeur on Cedrus libani, Marchalina caucasica Hadzibejli on Abies nordmanniana subsp nordmanniana, and Picea orientalis; Nemolecanium abietis Borchsenius, Physokermes hellenicus Kozaʾr & Gounari and Schizolachnus pineti on Abies bornmuelleriana; Lachnus roboris Linnaeus and Parthenolecanium rufulum (Cockerell) on Quercus spp. and Castanea sativa; Metcalfa pruinosa Say (Hemiptera: Flatidae) and Ricania simulans (Walker) (Hemiptera: Ricaniidae) on different host plants. All these insects produce large amount of honeydew depending on their population size. The article discusses the potential for these insects to produce honeydew honey.

Keywords: Picea orientalis, Abies nordmanniana, Ricania simulans, Eulecanium sericeum, Metcalfa pruinosa, Marchalina caucasica

   Effective and environmentally friendly methods of protection to reduce seed contamination from fungi are constantly sought. The use of thermal impulses of 100°C wet water steam to reduce fungal contamination has not been sufficiently investigated, and the potential of this physical approach has not been estimated.

   The aim of the study was to investigate what impact 100°C wet water steam with different time durations had on acorn contamination with fungi, acorn germination and biometric indicators of English oak (Quercus robur) seedlings during the first year of growth. Different treatment durations with wet water steam were used: 2, 4, 6, 8, 10, 12 and 14 s.

   Research showed that 6 seconds impact of wet steam on the surface of the oak acorn destroyed Alternaria spp., 8 seconds impact destroyed Penicillium spp. and 14 seconds impact destroyed Mucor spp. Using 14 seconds water steam treatment Penicillium, Alternaria and Mucor spp. fungi were eliminated.

   Wet water steam treatment for 2–4 seconds not only stimulated the acorns germination by 4.0–7.6%, but also had positive influence on the root collar diameter of seedlings. Wet water steam treatment for 2–12 seconds had a positive effect on the root development of oak seedlings, however, high temperature environment had a suppressive effect on the oak seedling height.

Keywords: biological control, wet water steam, fungi, oak acorns, seedling production

   The study was designed to determine whether cultivation of willow (Salix sp.) energy plantations (hereinafter WEP) is economically efficient and to identify the main factors that influence development of such plantations in Lithuania. The economic efficiency of the cul- tivation of WEP was estimated based on cash flow analysis, discounted cash flow net present value and decomposition analysis methods. The survey of the willow plantation growers identified the motives, incentives, problems and intentions of local willow growers. The study revealed that cultivation of WEP was mostly hindered by economic factors, including low selling price of willow biomass for fuel and high cost of harvesting. Willow cultivation in Lithuania was least hindered by social and ecological factors. The results suggest that European Union (EU) subsidies are currently the main incentive to cultivate willow plantations. However, financial support alone did not guarantee the success of willow biomass harvesting and market access of the final biofuel production. The findings of this study provide information for decision makers on the opportunities and challenges of the development of willow plantations in Lithuania.

Keywords: Salix sp., short-rotation plantations, social and economic factors, economic incentives

   The aim of the study was to assess changes in performance and competition for light of juveniles of seven forest tree species, Pinus sylvestris, Picea abies, Betula pendula, Alnus glutinosa, Populus tremula, Quercus robur and Fraxinus excelsior, grown in mono-species and mixed cultures with isolated potted roots under the impact of different combinations of climate change-related stressors, simulated in a phytotron under the elevated CO₂ concentration during one growing season, as follows: i) heat + elevated humidity (HW); ii) heat + frost + drought (HFD); iii) heat + elevated humidity + increased UV-B radiation doses + elevated ozone concentration (HWUO); and iv) heat + frost + drought + increased UV-B radiation doses + elevated ozone concentration (HFDUO). For the mixed cultures, three typical species’ mixtures were used: i) P. sylvestris, B. pendula and P. abies, ii) P. abies, B. pendula and Q. robur and iii) F. excelsior, A. glutinosa and P. tremula. For the control, the same material was grown outside the phytotron in ambient conditions.

   Analysis of variance (ANOVA) revealed that the effects of the complex treatments, species and species by treatment interactions were highly significant in most of the biomass, growth, physiological and biochemical traits studied. Pattern of species culture had highly significant effect on physiological and biochemical traits (except for H₂O₂ concentration); meanwhile it was of low significance for biomass and growth traits. Pattern of species culture by treatment interaction was highly significant in all traits, suggesting that the effects of the applied complex treatments vary depending on the pattern of species culture.

   Under the hot wet conditions the highest stem volume index, tree biomass, and growth were observed in deciduous P. tremula, A. glutinosa and B. pendula with more clearly pronounced differences in performance between different patterns of species cultures than in ambient conditions showing that the enhanced growth conditions facilitate revealing the potential and specific requirements of the fast-growers. P. abies in all treatments had lower stem volume index and tree biomass than in ambient conditions with no significant differences between the patterns of species culture, indicating that it suffered irrespectively of light availability in different cultures. The differences between performances of most tree species in mono- and mixed cultures in HFD treatment were rather small and nonsignificant. A complex HWUO treatment caused further reduction in tree biomass in all species and culture patterns except for mono-species cultures of A. glutinosa and B. pendula. The most complex HFDUO treatment had the strongest negative effect on biomass of almost all tree species compared to that observed in HW treatment, except for Q. robur and P. sylvestris which biomass and height increments remained higher than those in ambient conditions. This was due to relatively high drought tolerance and compensatory effects of the increased CO₂ concentration and temperature. Physiological and biochemical responses of species in different patterns of species cultures across treatments were very variable although often did not reflect in the effects on growth and biomass traits. The observed changes in performance of different tree species in different patterns of species cultures under various complex treatments allowed inferring that climate change may condition certain changes in competitiveness of some tree species resulting in atypical ecological successions of species and forest ecosystems.

Keywords: trees, complex treatments, controlled environment, competition, biomass, growth, physiology, biochemistry, phytotron