Aphids are characterized by a specific morphology and show a high biotic potential. Most species have been described from the temperate regions of the world. The purpose of the present research was to investigate the biology, population dynamics and harmfulness of Phyllaphis fagi (L.) (Hemiptera: Aphididae: Phyllaphidinae) on Fagus sylvatica (L.) and its two varieties ‘Pendula’ and ‘Atropunicea’. Demographic parameters of this aphid were tested in field conditions. Trees as isolated elements of greenery in the urban environment were taken into the consideration. The highest density of overwintering eggs was observed in the bark crevices of forking shoots. The shortest pre-reproduction and reproduction periods and the highest fertility was exhibited in the second generation of aphids. Pre-reproduction and reproduction periods of successive aphids’ generations were extended while females’ fertility was reduced. Despite of varied number of aphids on F. sylvatica and its two varieties, no significant differences were stated. Feeding aphids caused leaves’ curling downwards on both sides of the mid-rib. Clear damage was visible even during the presence of few individuals on the leaf. Decorative values of trees were reduced as early as in June.

Saccharomyces cerevisiae (SC) and Salix daphnoides bark (SD) water extracts were used for improving health-beneficial capacity of broccoli sprouts. The SC dilutions tested were 0.1, 0.5 and 1% (w/v), the SD concentration was 1% (w/v). Elicitation significantly modified the phenolics and flavonoid content, antiradical and chelating abilities, lipoxygenase (LOXI) and xanthine oxidase inhibitory activity (XOI). SC proved to be a better elicitor at a low concentration of 0.1% inducing antiradical, LOXI, XOI activities of both – hydrophilic and lipophilic extracts. SD water extract effectively induced lipophilic compounds with XOI activity and hydrophilic compounds with LOXI and antiradical activity. In most cases better results were obtained after one step induction. In the light of proved data nutaceutical value of non-processed food (broccoli sprouts) could be effectively enhanced by elicitation.

Strong vigour of apricot trees can be reduced by using the proper rootstock. Rootstock affects not only vigour but high and quality of yield and the lifespan of the trees as well. In autumn of 2006, the experiment with new apricot cultivars grafted on Myrobalan and ‘Wangenheim Prune’ seedlings was established at the Fruit Experimental Station near Wrocław. Trees of ‘Morden 604’ (as a control), ‘Goldrich’, ‘Harlayne’, ‘Hargrand’, ‘Darina’, ‘Sirena’ and ‘Kompakta’ cvs. were planted in four replications with two trees per plot. In comparison to Myrobalan seedling rootstock, the trees grafted on ‘Wangenheim Prune’ seedlings grew significantly weaker. The most vigorous genotypes were ‘Morden 604’ (control), whereas the least vigorous was ‘Kompakta’. Up to the 5^th year after planting, the highest total yield was recorded for ‘Morden 604’ and ‘Hargrand’ on Myrobalan seedlings. Significantly higher yields gave trees on Myrobalan seedling rootstock. The rootstock had no influence on mean fruit weight. In the autumn of 2010, most of dead trees was observed with ‘Darina’, especially on ‘Wangenheim Prune’ seedlings.

Sooty blotch and flyspeck is a fungal disease of complex etiology. SBFS fungi blemish the apple fruits surface reducing their market value. The aim of the study was to investigate the effect of fungi causing sooty blotch and flyspeck on apple during fruit storage. The experiments were conducted in 2007–2010. Fruits were collected from the orchard in Warsaw-Wilanów. Mass reduction in heavily and slightly infected or healthy apples per gram fresh weight of fruit was compared. Changes in quality of apples (wilting, wrinkling) were also observed during storage. Over a dozen to several dozen percent in reduction of the weight of heavily infested stored fruit as compared to a loss of fruit weight only slightly affected or healthy was found. It was also observed a wilting and wrinkling of the skin of heavily infested fruit.

Consumption of vegetables with either too low or excessive contents of micronutrients may have an adverse effect on human health. In intensive horticultural production mineral fertilizers, containing mineral or chelate compounds with varying micronutrient fertilization efficiency, constitute the main sources of micronutrients for plants. In the years 2009–2010 experiments with lettuce were conducted to investigate the effect of mineral (sulfates) and chelate (IDHA chelate, EDTA + DTPA chelate) forms of copper, zinc and manganese on yield and micronutrient contents in leaves. Two levels of micronutrients were applied (mg∙ dm^-3 of substrate): I. 5 Cu, 10 Zn, 10 Mn, and II. 20 Cu, 40 Zn and 40 Mn. Lettuce was grown in 6 dm³ containers filled with limed highmoor peat, enriched with macro- and micronutrients. Lettuce was harvested at the consumption stage. Contents of Cu, Zn and Mn were determined by ASA in lettuce leaves. The volume of lettuce yield at a lower content of micronutrients in the substrate did not depend on the form in which copper, zinc and manganese were introduced. After the application of higher rates of micronutrients in the mineral or IDHA chelate forms a significantly higher crop was produced than in case of EDTA + DTPA chelates. An increase in micronutrient rates in the substrate had a significant effect on an increase in their contents in vegetables. At the nutrition of crops with micronutrients at higher rates in the form of EDTA + DTPA chelates a significant increase was found in copper content in lettuce. After the application of higher rates of micronutrients plants that were introduced two micronutrients in the IDHA chelate forms and one in the mineral form contained less zinc. Leaves of lettuce grown on substrate with mineral forms of copper, zinc and manganese contained significantly more manganese than those grown in substrate with chelate forms of micronutrients.

In case of plants, inbreeding depression can be measured through comparison of the fitness of selfed individuals with outcrossed individuals. In this paper the effect of repeated inbreeding on fruit yield and yield component of strawberries (Fragaria × ananassa Duch.) was examined. Five strawberry cultivars (from 10 initial ones) including ‘Kent’, ‘Teresa’, ‘Senga Sengana’, ‘Chandler’ and the breeding clone 1387 were examined and self-pollinated in order to obtain first (S₁), second (S₂) and third (S₃) inbreeding generations. 5 cultivars differing in pedigree which were assumed to have the inbreeding coefficient of zero (F = 0) were compared with self-pollinated populations with expected inbreeding coefficients F = 0.5 (S₁), F = 0.75 (S₂) and F = 0.87 (S₃). The effects of different inbreeding levels were estimated for the following traits: number of inflorescences, number of flowers per inflorescence, fruit yield per plant, fruit number per plant, average fruit weight, weight of leaves per plant and pollen viability. Both positive and negative inbreeding depressions were found in many progenies in terms of the analysed characters. Weight of leaves per plant in S₁, S₂ and S₃ was affected the most (inbreeding depression ID = 62.5, ID = 66.2 and ID = 67.2, respectively). In the second generation (S₂), average fruit number per plant increased in comparison to S₀ (ID was -6.1). Inbreeding depression for average fruit weight per plant decreased in the successive inbreeding generations.

Celery is a valuable vegetable plants, due to the properties of dietary, medicinal and taste. It is moderately cold climate plant, well yielding in climatic conditions of our country, with proper selection of varieties and soil. A pot experiment carried out in two one-year series (2001 and 2002 year) examined the effect of various concentrations of Tytanit applied once and twice against NPK fertilization, in comparison to the control object and with mineral fertilization applied (NPK), on the yield of the total biomass, petioles and blades of celery, as well as the content of titanium, iron, manganese and copper. Those elements fulfil a primary role in the process of photosynthesis and (according to literature data) titanium also plays an important function in this process. It was found that foliar fertilization with Tytanit had a favourable effect on increasing the test plant yield. The highest yield of celery biomass was obtained after applying the highest dose of Tytanit. The frequency of spraying resulted in slight changes in the yielding of the test plant. A higher average bioaccumulation of titanium, iron and manganese was observed in blades than in petioles, in series I and II of the study. The highest concentration of Tytanit applied once and twice resulted in a decreasing bioaccumulation of Fe and Mn in the examined parts of celery, in series I and II of the study. The highest amounts of Cu were observed on the control object fertilized with NPK and under the influence of Tytanit application in the lowest concentrations. The average uptake of Ti and Mn with the yield of blades was twice as high as the yield of petioles, while in the case of Fe and Cu, it was higher with the yield of petioles than of blades.

Determination of the optimal types and concentrations of plant growth regulators as medium constituents is one of the most important factors of successful micropropagation. With the aim of optimization of in vitro multiplication of Clematis viticella and Clematis ‘Petit Faucon’ the effect of following cytokinins on growth and branching was studied: benzyladenine (BA), isopentenyl adenine (2iP), kinetin (KIN) and thidiazuron (TDZ). The obtained results show that KIN at concentration of 10 mg·dm^-3or 5 mg 2iP∙dm^-3 are the best for proliferation of Clematis viticella shoot tips while nodal parts produce more axillary shoots on the media with 2iP at concentration of 0.62 mg·dm^-3. Shoot tip explants of Clematis ‘Petit Faucon’ produce the most axillary shoots in the presence of 20 mg 2iP∙dm^-3 or 10 mg KIN∙dm^-3 and nodal ones branch best on the media with addition of 1.25 mg 2iP·dm^-3.

The quantity and quality of the herb material are reduced by pathogenic fungi. In the case of caraway this pathogen is Septoria carvi. In the vegetation periods the fungus occurs with varying intensity, which is related to the requirements of life. The present study found that the growth of fungal colonies is possible at the temperatures from 0 to 30°C, the optimum being from 20 to 25°C, and sporulation is possible at the temperatures from 10 to 30°C, with the optimum at 25°C. It was shown that the most useful medium for the isolation of S. carvi from caraway plants is malt medium and malt medium with decoction of the leaves of this plant. Pycnidia and conidia of the fungus, which are necessary to identify the species, are formed the fastest on the malt medium with decoction of the leaves or schizocarps of caraway and on PDA medium and it is these substrates that should be used for the cultivation of S. carvi.

The eggplant is a valuable plant mainly grown in a greenhouse and under the foil. Nowadays we have still too little informations about nutritional and fertilization need of that plant. Experiments involving eggplant of Epic F₁ cv. were carried out in 2004–2005 in unheated foil tunnel; the aim focused on evaluating the influence of pruning methods using plants treated with nitrogen in form of N-NH₄, N-NO₃, NH₂ applied at various rates. Achieved results revealed significantly influence of nitrogen forms on total nitrogen, phosphorus, and calcium, while no influence on potassium and magnesium contents in eggplant leaves. Instead, increasing nitrogen doses significantly elevated the nitrogen, phosphorus, and magnesium concentrations in plants. Improved light conditions within a plant profile due to cutting had positive effects on phosphorus and calcium contents in leaves as compared to plants pruned in their natural form. Considerable decrease of the subsoil pH value was recorded after applying the increasing rates of nitrogen fertilizers in a form of ammonium sulfate. Following levels of eggplant nutrition at full ripeness were considered as optimum: 0.28% to 0.45% N-NO₃ and 3.70 to 4.00% N-tot. in leaves, as well as 250 to 350 mg N-NH₄+N-NO₃·dm^-3 in subsoil.

Effect of growth regulators on postharvest longevity of Zantedeschia albomaculata /Hook/ Baill.) leaves was evaluated in studiem. The aim of 3 experiments to evaluate the effect of topolin used in two forms: meta-methoxytopolin (MemT) and its riboside (MemTR) on postharvest longevity of ‘Albomaculata’ leaves. In the first experiment, the topolins were used in water solutions at concentrations of 25, 50 and 75 mg·dm^-3 for 4-hour conditioning of leaves, which were then placed in distilled water. In the second experiment, their solutions at concentrations of 25 and 50 mg·dm^-3 were employed for 24-hour conditioning of leaves in a cold room at a temperature of 5°C and for a short, seconds-long immersion of leaf blades. In the third experiments, the scheme of the second experiment was employed again, except that here the solutions contained not only the topolins but also gibberellic acid at the same concentrations. In the experiments the control was leaves placed in distilled water after cutting. MemT and MemTR affect the postharvest longevity and quality of conditioned leaves of the cultivar Albomaculata. At concentrations of 25–75 mg·dm^-3 they extend their longevity and inhibit protein degradation, but have no effect on their greenness index. Applied at concentrations of 25–50 mg·dm^-3 to soak leaf blades for a few seconds, both growth regulators improve the longevity of the leaves more effectively than their 24-hour conditioning. The combination of MemT with GA₃ at concentrations of 25 + 25 and 50 + 50 mg·dm^-3 to soak leaf blades for a few seconds extends the postharvest longevity of the leaves by an average of 14–24 days and inhibits protein degradation, but has unfavourable effect on their greenness index.

In Poland edible honeysuckle becomes more and more popular, especially in amateurish cultivation. There is a little information about cultivation technology. The aim of this study carried out in 2008–2009 was to examine the influence of Goëmar^® BM 86 and calcium nitrate on yielding and fruiting quality of two cultivars of blue honeysuckle (Lonicera caerulea var. kamtschatica): ‘Atut’ and ‘Duet’. Using the fertilization with calcium nitrate, applied to the soil around plants, in April at the rate of 50 kg·ha^-1, alone or with Goëmar^® BM 86 (applied three times during the bloom period at the dose of 3 l·ha^-1) was compared to untreated plants. Fertilizers had no positive effect on the yield and the mass of 100 fruit. Fertilizers did not influence significantly on the dry matter, soluble solids, reductive sugar and anthocyanins content. The influence of Goëmar^® BM 86 and calcium nitrate on acidity of berries was inconsistent. Honeysuckle berries of cv. ‘Atut’, after using the mentioned combination of preparations, reacted by increasing in acid concentrations, however acid content of ‘Duet’ berries significantly decreased in comparison to the control. The quality features of honeysuckle berries were strongly dependent on the weather conditions during vegetation period.

Organic manuring is suggested to be necessary in sweet corn cultivation. It is not always possible to use farmyard manure due to economic, production or technical reasons. Catch crops used as green manures can be an alternative source of organic matter. A field experiment was carried out in central-eastern Poland to investigate the effect of phacelia and amaranth catch crops used as green manures on sweet corn growth and yields. Catch crops were sown at three dates: 21^st July, 4^th and 18^th August, and incorporated in late October. Sweet corn was cultivated in the first year following manuring. The effect of the green manures was compared to farmyard manure applied at a rate of 40 t∙ha^-1 and a non-manured control. Of the catch crops examined, the highest yield of fresh and dry matter was obtained for phacelia sown on the 21^st of July (33.6 t∙ha^-1 f.m. and 6.3 t∙ha^-1 d.m.) and 4^th of August (33.7 t∙ha^-1 f.m. and 5.5 t∙ha^-1 d.m.). A delayed sowing date of phacelia seeds, from 21^st of July to the 18^th of August, caused a decrease in the quantity of fresh matter and dry matter by 26 and 37%. Amaranth sown on the 21^st of July produced 26.2 and 5.3 t∙ha^-1 fresh and dry matter. Delaying the sowing date of amaranth seeds by 14 and 28 days decreased the yield of fresh and dry matter by 18 and 55–58%. There were found similar effects on yield of farmyard manure, phacelia and amaranth catch crops sown on the 21^st of July. Delaying the sowing date of catch crops by 2 and 4 weeks decreased the marketable yields of corn cobs by, respectively, 16.2 and 28.9% for phacelia and by 12.8 and 24.4% for amaranth. The average weight of marketable corn cobs cultivated after farmyard manure, phacelia and amaranth catch crops sown on the 21^st of July and phacelia sown on the 4^th of August were similar. Biological productivity of corn cobs following farmyard manure and the catch crops examined (except amaranth sown on the 18^th of August) was similar and ranged from 66.5 to 72%. ‘Chalenger F₁’ produced marketable cobs with a higher average weight but with lower biological productivity than ‘Sweet Wonder F₁’.

Sweet corn grain is rich in nutrients. There are many factors, fertilization being one of the most important, which influence the quality of the grain. A special role in improving soil fertility is ascribed to catch crop plants when they are incorporated into the soil. A field experiment was carried out in central-eastern Poland to investigate the effect of phacelia and amaranth catch crops used as green manures on dry matter, sugars and ascorbic acid contents in sweet corn kernels. Catch crops were sown at three dates: 21^st July, 4^th and 18^th August, and incorporated in late October. Sweet corn was cultivated in the first year following manuring. The effect of the green manures was compared to farmyard manure applied at a rate of 40 t∙ha^-1 and a non-manured control. The highest average dry matter content (27.5%) was determined in corn kernels cultivated without manuring, significantly lower after farmyard manure (26.4%). Catch crops incorporation did not cause significant changes in dry matter content in corn. Corn cultivated after catch crops had higher or similar contents of sugars compared with cultivation after farmyard manure. The most total sugars (8.12% f.m.) were found in corn cultivated after phacelia sown on the 21^st of July, the least (7.04% f.m.) in the non-manured control. The highest monosaccharides content was in corn following amaranth sown on the 21^st of July and 4^th of August (2.50% f.m.), it was significantly lower (2.27% f.m.) after farmyard manure. The highest ascorbic acid content was determined in corn after phacelia sown on the 4^th of August (8.88 mg·100^-1 g f.m.) and in amaranth sown on the 21^st of July (8.98 mg·100^-1 g f.m.). Significantly less ascorbic acid was found following phacelia sown on the 18^th August and in the non-manured control. Ascorbic acid contents in corn from the remaining treatments did not differ significantly. ‘Sweet Wonder F₁’ was characterized by higher contents of dry matter and total sugars in kernels than ‘Challenger F₁’.

Artichoke is known as a valuable vegetable (for its eaten buds), popular in the countries bordering the Mediterranean Sea, in the USA and South America, or medicine with documented hepatoprotective, choleretic, antioxidative, anticancerogenic, cholesterol-reducing and diuretic action. When it is cultivated for pharmaceutical purposes artichoke should be obtained from one-year-old plantations, characterized by high amount of active substances (CQA and flavonoids). The objective of three year field study was to evaluate the effects of different methods of plantation establishment: direct seed sowing, seedlings produced in multicells transplanting, seedlings with ‘bare roots’ from nursery beds transplanting as well as plant densities: 3.3 and 4.2 units∙m^-2 in artichoke (Cynara scolymus L.) cv. Green Globe culture. Additionally, quality of raw material obtained in two following cuts (performed in August and October) was estimated. Generally, traditional method of plantation establishment by direct seed sowing results in lower yields of worse quality of artichoke raw material (characterized by significantly lower active substances content), while, seedlings produced previously in multicell trays in plastic tunnel transplantation could be indicated as better method of artichoke plantation establishment for pharmaceutical purposes. A decrease of artichoke yields and dimensions but at the same time tendency to significant improve its quality (on an average two times higher content of flavonoids and CQA in comparison to direct seed sowing) was noted when seedlings transplantation from plastic tunnel (with ‘bare roots’) was used as method of plantation establishment. Increasing plant density of 3.3 to 4.2 units∙m^-2 caused a decrease of size and weight (by 13,4%) of individual plant leaves, and at the same time an increase of their numbers, and total yields harvested from the unit area (by 0.2 t·ha^-1). Moreover, during the second cut significantly higher (by 27%) yields of better quality artichoke leaves (characterized by higher flawonoid and caffeoylquinic acids content) were obtained.

In many countries, apart from creative cultivation, clone selection is also carried out to get the most valuable rootstocks for apple trees. In years 2008–2010, in the Department of Dendrology and Nursery Production of University of Life Sciences in Poznań, an experiment, which is described below, was conducted. Its aim was to estimate a degree of morphological, phenological and genetic variability of 15 clones originating from crossing A2 and B9 rootstocks. Observations that were carried out confirmed variability of the above mentioned features of clones. The differences were found in morphology of shoots, leaves, buds and in terms of the beginning of vegetation. Analysis of the results made it possible to separate four clones with desired feature of the reduction of the vigour of growth. The clones were marked as number 5, 11, 12 and 13, and they can turn out to be valuable rootstocks for apple trees. With help of PCR-RAPD method genetic variability of the clones number 2 and 3 was shown, as well.

Abstract: Leaf chicory type belongs to valuable vegetables in terms of its high nutrition and taste qualities. In spite of those advantages, in Poland, chicory is relatively little known. The purpose of field experiment carried out in the years 2009–2010 was the assessment of possibility of cultivation different types and cultivars of salad chicory in climatic conditions of Lower Silesia. In the experiment there were used 9 types of chicory: ‘Palla Rossa 3’, ‘Orchidea Rossa’, ‘Rosso di Verona’, ‘Grumolo bionda’, ‘Capotta di mantovana’, ’Pan di Zucchero’, ‘Rosso di Treviso 2’, ‘Rosso di Chioggia’, ‘Variegato di Castelfranco’ and two breed cultivars ‘Indigo’ and ‘Fidelio’. The highest marketable yield was recorded for ‘Grumolo bionda’ (4.24 kg∙m^-2) and ‘Capotta di mantovana’ (4.00 kg∙m^-2), while the lowest one characterized ‘Fidelio’ cv. (1.27 kg∙m^-2) and ‘Rosso di Chioggia’ (1.56 kg∙m^-2). The highest amount of nitrates was observed in ‘Rosso di Verona’ –1063.60 mg NO₃∙kg^-1 and the lowest quantity – in ‘Indigo’ cv. (302.23 mg NO₃∙kg^-1). The highest phosphorus content featured the plants of intensive red leaves (0.50 do 0.58% s.m.), while the highest quantity of calcium green – leaf plants. Average magnesium content in chicory leaves equaled 0.20% f.m.

Abstract: Foliar fertilization is fairly frequently applied besides to fertilization to the roots. In the years 2003–2005 a study was conducted on the effect of foliar feeding with phosphorus on the yielding and content of mineral element in leaves of highbush blueberry. The experiment was conducted on a production plantation, on 10-year old bushes of ‘Bluecrop’. The foliar fertilizer Insol Fos was applied at 4 concentrations: control – 0%; 0.4%, 0.8% and 1.2%, several times at intervals of every week (7×), every 2 weeks (4×), and every 3 weeks (3×). The first treatment was applied at the beginning of the 3^rd decade of May and the final one at the beginning of July, minimum 7–10 days prior to the first harvest of berries. Foliar sprays with Insol Fos had a positive effect on the yielding of highbush blueberry, but it had no effect on the weight of 100 fruits. The highest concentration of the fertiliser proved to be the most effective. Irrespective of the concentration applied, in the years of the experiment the best yielding were those plants that were foliar-applied every 2 weeks. Foliar fertilization with the fertilizer Insol Fos had a varied effect on the content of mineral elements in the leaves of highbush blueberry, causing a significant increase in the content of N, P and Mg, and a decrease in the concentration of K and Ca.

Pot marigold (Calendula officinalis L.) is an annual ornamental plant which is also grown for herbal raw material used in the pharmaceutical and cosmetic industries. There are a lot of pot marigold cultivars which differ in colour and in size of inflorescences as well as participation of ligulate flowers. In the field experiment there were five cultivars of pot marigold compared: ’Orange King’, ‘Persimmom Beauty’ ‘Promyk’, ‘Radio’ and ‘Santana’. As far as morphological features are concerned ‘Orange King’ turned out to be the best. It produced the most numerous and shapeliest inflorescences, with the biggest number of ligulate flowers. Raw material yield of compared cultivars oscillated from 849 to 1661 kg·ha^-1 of flower heads, and the ligulate flowers themselves from 449 to 1141 kg·ha^-1. In both cases the highest yield was obtained by ‘Orange King’, and the lowest by ‘Promyk.’ The content of biologically active compounds in inflorescences of particular cultivars also varied: flower heads of ‘Persimmom Beauty’ contained the highest amount of essential oil (0.41 ml·100 g^-1), whereas ‘Promyk’ contained the highest amount of flavonoids (0.56% – expressed in hyperoside). In all cultivars inflorescence receptacle gathered the highest amount of essential oil and ligulate flowers gathered the least. The opposite tendency appeared in the case of flavonoids.

Mineral nutrition of apricot is very specific and depends on different factors such as soil fertility, soil pH, weather conditions, cultivars, rootstocks, fertilizers, age of trees etc. For these reasons, during 2008 and 2009 we evaluate nutrient status of five apricot cultivars (Vera, Aleksandar, Biljana, Harcot, Roxana) at 120 days after full bloom (DAFB) grown on acidic soil in the region of Čačak (Western Serbia). The results showed no statistically significant variations in the N, K and Ca content of apricot leaves among cultivars, as opposed to significant differences in the content of P, Mg, Fe, Mn, Cu, Zn and B. The ΣDOP index revealed that the average content of all macro- and micronutrients was below the optimum, except that of P in both years and that of Mn and Cu in the first year of the study. The insufficient nutrient supply of the test apricot cultivars requires adjustment of fertiliser types and application rates to this soil type according to foliar analysis.

Green moulds of Trichoderma genus cause high losses in oyster mushroom cultivations in many countries. Recently two new species i.e. T. pleurotum and T. pleuroticola have been identified. In the experiment yielding levels of Pleurotus ostreatus growing on substrates infected with Trichoderma isolates were investigated. The following Trichoderma isolates were used: T. pleurotum designated as KWK/17 and T. pleuroticola designated as KMS/21 as well as three wild strains and one cultivated strain of P. ostreatus. It was found that the substrate infections with T. pleurotum and T. pleuroticola isolates caused significant yield reductions of the examined strains of oyster mushrooms. The infection with the T. pleuroticola KMS/21 isolate caused a significantly higher yield drops than the infection with the T. pleurotum KWK/17 isolate in comparison with yields recorded from uninfected substrates.