The aim of the study was to verify whether methanolic extracts prepared from plants of 26 selected species contained substances reducing feeding of Hylobius abietis beetles on shoots of Pinus sylvestris. Experiments were conduced under laboratory conditions. A statistically significant reduction in the size of damage was recorded on pine twigs treated with methanol extracts of leaves of Trifolium repens, Lupinus polyphyllus, Robinia pseudoacacia, Tanacetum vulgare, Nicotiana tabacum, Sambucus nigra, Convallaria majalis and Lycopersicon esculentum. Probably the strongest antifeedants were methanolic extracts of leaves of Lupinus polyphyllus, Robinia pseudoacacia and Convallaria majalis.

The aim of the study was to determine whether extracts of tobacco leaves may reduce feeding of the large pine weevils on twigs of pine – Pinus sylvestris. The research was conducted in laboratory conditions. The research proved statistically significant decrease in damage size on the pine twigs as a result of application of each tested extract.

The purpose of the research was the comparison of capturing effectiveness of large pine weevils with different types of traps. The research was conducted in the forest of Oborniki forest division (RDLP Poznań). It has been shown that most large pine weevils are captured by the IBL-4 type trap. The least effective trap turned out to be the trap log.

The influence of Fastac 100 EC, Marshal 250 CS and Nomolt 150 SC insecticides on the (L₁) caterpillars of Siberian Silk Moth (Dendrolimus superans sibiricus) was investigated. Three different concentrations were prepared for each insecticide. It has been shown that all variants of the tested insecticides reduced the population of the larvae, whereby in case of Fastac 100 EC infusion, no statistically significant differences between the investigated concentrations were obtained. The most effective insecticide was Fastac 100 EC which, regardless of the concentration used, caused 100% mortality within 48 hours from application.

The total of 35 splendid pear trees was inventoried in the Citadel Park and they constitute approximately 13% of the most valuable trees in this park. The circumferences of the measured trees ranged from 150 to 264 cm. Considerable circumferences were determined in the case of 32 pear trees, of which 11 trees had monumental circumferences and 21 specimens – close to monumental circumferences. From among 14 trees found to be in a very good health condition and having monumental or close to monumental circumferences, “candidates” for legal protection in the form of nature monuments should be selected.

This paper presents the process and the results of studies on fungitoxicity level of the chosen phenolic compounds occurring in wood that can be responsible for the natural resistance of this material to decay by fungi. All together 14 substances were examined: Eugenol, Vanillic acid, Isoeugenol, Cyclohexanone, Resorcinol, Syringaldehyde, 2,6-dimethoxyphenol (Syringol), Pyrogallol, 4-methoxybenzoic acid (Anisiic acid), 2-furaldehyde, Furanone, 4-allyl-2,6-dimethoxyphenol, Tetramethyl-4-butanediamine and 3',5'-dimethoxyacetophenone and 6 different mixtures of these compounds imitating their natural coexistance in wood. For the tests the modified AG nutrient agar medium method based on using a series of media plates of various saturations of the tested substance was used. Trametes versicolor and Laetiporus sulphureus served as the test fungi. All together 20 variants of the experiment were pursued on 2400 plates. On this basis the fungitoxicity level of each substance was determined and they were evaluated in regards of their potential usefulness in the practical protection of trees and wood.

A comprehensive analysis has been made of the mechanical properties and density of 100 timber species. The correlation between the mechanical properties and wood density has been approximated by a power function type y = aρⁿ. No functional relation has been found between the parameters describing mechanical properties of the cell wall and the wood density. The values of these parameters show great scatter of about ±50% relative to the mean value. An attempt has been made to identify other wood characteristics determining the mechanical properties of wood. The species characterised by extremely high values of the parameters describing mechanical properties of wood have been singled out. The greatest differentiation in the values has been noted for the tensile strength. Among the coniferous species of similar density the differences have reached 113% on average, while among the deciduous species – 143%, at the differences in density being only of 15%.