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HR  EN   

3-4/2014

WEB EDITION


Scientific-technical and professional journal
of Croatia Forestry Society
                         Issued continously since 1877.
       First issue of this web edition start with number 1-2/2008.
   ISSN No.: 1846-9140              UDC 630*https://doi.org/10.31298/sl
PAPER EDITION
DIGITAL ARCHIVE

HRČAK
Portal of scientific
journals of Croatia
   Issued by: Croatian Forestry Society

   Address: Trg Mažuranića 11, HR-10000 Zagreb, Croatia
   Phone/fax: ++385 1 4828477
   e-mail: urednistvo@sumari.hr
   Editor in Chief: Boris Hrašovec


     
 
RIJEČ UREDNIŠTVA
 
Uredništvo   121
THE STATUS AND POSSIBILITIES OF A MORE ACCURATE EVALUATION OF FORESTS AND FORESTRY AS PART OF THE ECONOMY OF THE REPUBLIC OF CROATIA      
EDITORIAL
As we can see from the above, both the Constitution and the Forest Law emphasise the importance of forests and forestland for the Republic of Croatia and regulate management with this specific natural resource. The question now remains: do we apply the specific planning and management method in practice, or do we manage this resource according to political dictates and treat it as one would treat a shoe factory which could go bankrupt tomorrow with little national con- sequence. If the 15 non-timber forest functions listed in paragraph (2) are not there only for declarative purposes, but should be respected for their immeasurable value, then the proportion of forestry in the whole economy requires different evaluation. Based on the principle arising from scientific research in Western Europe, the value of forest functions are estimated to be up to 50 times higher than the value of timber as raw material. Our intention here is not to discuss the fee for non-timber forest functions or who should pay it, but only to state in general how much they might be worth (20 or more times higher on average), and add them to the value of timber as raw material.
Accordingly, the calculation of these values is based on the value of timber as raw material and the appraisal factor of non-timber forest functions. The value of timber as raw material depends on the quantity, quality and price of a wood product, where the quantity and quality are defined by the management method contained in the Management Plan and the price is defined by the market. What follows are questions to which we are expected to provide answers. Do we manage this specific natural resource by adhering to the Management Plan and the principle of sustainable management? Do we skip, for various reasons, the prescribed forest treatments in terms of time and quality, and do we, by doing so, decrease the non-timber forest function, thus influencing the quantity and quality of raw wood material? Finally, do we utilize the productive capacities of a forest site to the optimum?
With regard to the available quantity and quality of raw timber, we should provide answers to two more questions: do we use all the available raw wood material and how do we use/sell the most valuable raw wood material – as raw material in the literal sense of the word, as a semi-product or as a final product, which also determines the proportion of forestry in the national economy? We finally arrive at the price of raw wood material and the question whether this price is dictated by the market or is a remnant of "planned economy". As long as domestic demand is up to three times higher than the supply of certain wood assortments, as long as it is more profitable to manufacture parquet flooring from the best quality wood material (instead of processing) than make high quality final products, use wet wood to make pellets or transport wood chips and sawdust above financially limiting transport distances (Hungary, Austria, Italy and then the home market), the prices will definitely not be market prices. How it is possible that prices in market economy are determined by the state? Who do we protect and for what reason do we irresponsibly squander our national treasure?
About 80 % of the forests and forestland is state owned in terms of area and about 95 % in terms of value. All this wealth has been entrusted to the state company Hrvatske Šume Ltd, who has been in the restructuring process for almost 20 years. Here is a sentence taken from the text by Ž. Ivanković (Večernji List): "According to scientific analyses, privatisation was dominated by so-called defensive restructuring and cutting down on work posts, unlike other transitional countries where privatisation was characterized by development, launching new products and conquering new markets". Taking all the above into account, we ask more questions: is our case also the case of "defensive restructuring", and why Austrian foresters, for example, know how to perform tourist-based jobs at their facilities and we do not, or why they sell energy while we sell wood chips in minimal quantities instead of the currently available quantities, or even much higher quantities in the future, by which we would significantly decrease the import of fossil fuels? If we give honest answers to these and other questions, we shall arrive at the answer to the question in the headline. More importantly, if we manage to pass these questions and answers to the competent Ministry and the Croatian Government, maybe the current attitude towards forestry as one of the most important branches of Croatian economy will change for the better.
Editorial Board


    authors:
    Uredništvo
 
 
IZVORNI ZNANSTVENI ČLANCI
 
Jura ČAVLOVIĆ, Krunoslav TESLAK, Karlo BELJAN  UDK 630*569+653+231 (001) 123
THE EFFECTS OF DIFFERENT STAND REGENERATION PLANNING ON MANAGEMENT AND PEDUNCULATE OAK FOREST DEVELOPMENT – A SMALL SIZE MANAGEMENT CLASS CASE STUDY      
Summary
Pedunculate oak forests in Croatia are characterized with an irregular age-class distribution (larg share of mature stands), pedunculate oak dieback and decreasing stand structure quality, as well as large sized stands and they spatial heterogenity (density of pedunculate oak). Future management and development of the forest depend on actual age-class structure, intensity and spatial-temporal dynamics of forest regeneration. Thereby, spatial dividing of an appropriate size areas (new stands) and defining priority of their regeneration over future periods, which should be based on an objective criteria (e.g. potential rent difference as a consequence of the decision of regeneration (prompt or adjournment) of a potentially mature pedunculate oak stands), is key question. Based on developed computer program application, paper aim is to research effects of two opposite approaches of regeneration priority stand ranking and different intensities of forest regeneration on: stands growth, development of age-class structure and spatial forest structure, as well as possible trends in amounts and values of future revenues.
Object of the research is real even-aged forest (management class of pedunculate oak) in Opeke management unit. Area of the forest is 429.5 ha divided into 26 stands of average area of 16.5 ha. Youngest stand is 107 years old and the oldest is 185 years. There is large deviation between actual and theoretical age-class distribution of the forest (table 1).
Projection of management and spatial-temporal development of the even-aged pedunculate oak forest over future fourteen 10-year periods (rotation) is performed by computer program SIMPLAG (Teslak i dr., 2012). Within "theoretical" intensity of regeneration (30 ha in 10-year regeneration area, 2–6 ha stand regeneration size, 250 m minimal distance between regenerated stands), and intensive regeneration (50 ha in 10-year regeneration area, 3–13 ha stand regeneration size, 250 m minimal distance between regenerated stands), there were two approaches of regeneration priority stand ranking:
– stand regeneration ranking according to lowest potential rent difference (poor structure stand has highest regeneration priority – NSR);
– stand regeneration ranking according to highest potential rent difference (well structure stand has highest regeneration priority – OSR)
Different management approach validation is performed using comparison and deviation indices (actual vs. theoretical management criteria average deviation).
Results showed that less intensive regeneration approach with appurtenant requirements would lead to development of an optimal forest structure as to larger number, smaller sized (5 ha average area), and more homogeneous stands (fig. 1a). Development of age-class forest structure has indirectly manifested in trends of average stand age (fig. 1b). An approach of intensive forest regeneration would result with fast decrease of average stand age, oscillating around theoretical stand age and never would achieve theoretical age-class structure. A question of maintenance and conservation of pedunculate oak stands for long period, up to stand age above 250 years, is very important, particular in a case of less intensive regeneration over long regeneration period of forest.
Influence of forest regeneration intensity and approach of regeneration priority stand ranking on trends and total amont of forest growing stock, intermediate and regeneration fellings (fig. 2, tab. 2 and 3), as well as on value of fellings (fig. 3, tab. 2 and 3), has obtained. More intensive regeneration would result with larger average growing stock, total fellings and gross/net value of fellings, meanwhile with large deviations around theoretical models. Approach of priority regeneration of poor quality stands would achieve larger amounts of fellings and revenues too, but with less deviations, what is in terms of sustainability, more acceptable.
Future forest management for the forest (and forests of such structure) based on gradually forest regeneration over longer period, by priority regeneration of areas up to 5 ha within poor quality structure parts of current forest stands (new stands), is recommended. This management approach would lead to forming of an appropriate spatial forest structure and development of a balanced age-class structure, with the highest ecological and economic effects.

Key words: pedunculate oak; age-class distribution; stand structure; rent; regeneration priority; planning of regeneration felling

    authors:
    ČAVLOVIĆ, Jura      ŠL
    TESLAK, Krunoslav    ŠL
    BELJAN, Karlo    ŠL
 
Dalibor Ballian, Alma Hajrudinović, Jozo Franjić, Faruk Bogunić  UDK 630*164
(Quercus trojana Webb.) (001)
135
MORPHOLOGICAL VARIABILITY OF THE LEAVES OF THE MACEDONIAN OAK Quercus trojana WEBB.) IN BOSNIA AND HERZEGOVINA AND MONTENEGRO      
Summary
A morphometric analysis of the leaf traits of Macedonian Oak (Q. trojana) in its north-westernmost range was conducted, including in total 130 individuals from 13 natural populations in Bosnia and Herzegovina and Montenegro. The purpose of the study was to use the analysis of variance for the morphological characteristics of leaves from small and markedly fragmented populations to determine if there are any patterns of population differentiation and detect the morphological characteristics associated with such differentiation.
The Principal Components Analysis (PCA) did not identify the existence of discrete groups but rather of a continuous gradient in the variation of morphological characteristics and the absence of geographical population patterns. The morphological characteristics most closely related to population differences displayed relatively low to moderate values with PCs whose maximum correlation values were ≤ 0.554. The results of a cluster analysis conformed to the PCA results, indicating two population groups, which equally display no geographical pattern. The results of descriptive and univariate statistics pointed to marked variability of morphological leaf characteristic between populations and the presence of significant differences among individuals.
Finally, it should be noted that the study of populations of Macedonian Oak in its north-westernmost range identified a high degree of variability in the morphological leaf characteristics studied, and indicate that many different factors impact on the patterns of the small and fragmented populations of this species in Bosnia and Herzegovina and Montenegro. Further research on a larger sample, using molecular markers, will contribute to a better and more accurate knowledge of Macedonian Oak variability in this part of its natural range.
Since this is a sub-Mediterranean region, and Macedonian Oak is a very important tree species from ecological point of view, thus conservation by in situ method in all open and preserved areas is recommended, with particular attention to the origin of the forest reproductive material for reintroduction to degraded habitats, as suggested by the results obtained.

Key words: Quercus trojana; leaf morphology; inter- and intrapopulation variability.

    authors:
    Ballian, Dalibor  
    Hajrudinović, Alma  
    FRANJIĆ, Jozo      ŠL
    Bogunić, Faruk  
 
Krunoslav Arač, Milan Pernek  UDK 630*453 (001) 145
OCCURRENCE AND SPREADING OF THE LARGE LARCH BARK BEETLE (Ips cembrae) IN CROATIA AND POSSIBLITIES OF MONITORING BY USING PHEROMONE TRAPS      
Summary
The large larch bark beetle (Ips cembrae) is a secondary pest species which tends to build outbreaks in certain condition particular after drought stress or thinning. If enough suitable material is available in the forest, population density starts to grow and in lack of weakened trees the bark beetles attack healthy trees. In such circumstances this beetles are considered as primary pests. Regarding new problems with this bark beetle species in Croatia and trends of environmentally friendly forest protection measures, it is essential to determine the occurrence and possibilities of population spreading of the large larch bark beetle and gain new knowledge about possibilities for using pheromone traps against this pest.
The results are showing occurrence, distribution and damage of large larch bark beetle in Croatia. Although large larch bark beetle has been mentioned in several publications as present in Croatia, there is no provable evidence of this because no locality has ever been given neither in publications nor entomological collections. Therefore the record of large larch bark beetle in Koprivnica on European larch (Larix decidua) in October 2008, could be considered as the first record of this pest species in Croatia. The large larch bark beetle was recorded from 2008 till 2013 at 24 forest sections in 7 Forest districts, in 23–58 old stands at elevation of 160–350 a.s.l. The distribution map shows the infection spreading which amounts up to 17km yearly. For monitoring purpose pheromone traps (Theysohn®) baited with Cembräwit® were installed in 2011. The monitoring was observed trough the vegetation period from 2011 till 2013 which is the first pheromone trap monitoring of this species in Croatia. It was found that the first generation is swarming in middle April. Further only one generation was recorded till 2012 and just in 2013 a second generation occurred in August and September. The damage of this pest was assessed by number of marked trees and timber volume of felled trees. In total 4.922 larch trees were infected which is 2.121m3 timber volume. The majority of timber volume was marked for felling in 2012 and 2013 probably influenced by drought combined with high temperature and very long periods without precipitation. In such conditions larch trees were highly stressed and physiologically weakened. This was the trigger for bark beetle attack. In the coming years a further spreading to new locations in Croatia is expected.

Key words: Ips cembrae; Larix decidua; Theysohn®; Cembräwit®; pheromone trap; bionomy

    authors:
    ARAČ, Krunoslav      ŠL
    PERNEK, Milan      ŠL
 
Maja Popović, Mladen Ivanković, Saša Bogdan  UDK 630* 165 + 181.8 (001) 155
VARIABILITY OF HEIGHT GROWTH AND SURVIVAL OF PROGENIES FROM PEDUNCULATE OAK (Quercus robur L.) SEED STANDS AT THE FIELD TRIAL ‘JASTREBARSKI LUGOVI’ – FIRST RESULTS      
Summary
Previous studies of morphological and physiological trials of pedunculate oak in Croatia revealed genetic differentiation of local populations as well as high degrees of genetic diversity within each population. For further research of genetic diversity and differentiation of oak populations in Croatia, height and survival were analysed in a newly genetic test which contains progeny from 16 seed stands and one regular management forest stand (Table 1) at the age of four and five years, respectively (Figure 1 and 2). Survival for first analysed year was extremely good, but after the next vegetation period visibly decreased. Analysis of variance for mean height of two consecutive years (2010th and 2011th) revealed significant differences between populations (Table 2 and 3). Depending on the position within the genetic test same populations or families had different "dispersal" of mean height. We conducted a Tukey-Kramer test of the least square mean difference of population heights in order to determine their relationship, and to determine a possible geographic pattern of genetic differentiation (Table 5 and 6). Population HR 88 (FA Našice, Forestry Office Koška, Working unit Lacić-Gložđe) in both years differentiated as the highest of all, while other isolated groups of populations multiple overlapped. Comparing the significant difference in average height between populations and their geographic location geographic pattern of differentiation could not be observed (Table 5 and 6).
An analysis of phenotypic plasticity of the studied populations for population height at age of 5 years was performed (Table 7) because of statistically significant effect of blocks. No geographic pattern of differentiation between populations was observed for the plasticity indices (PIv, RDPI) (Table 8). Populations were categorized into phenotypically stable, unstable, and with average phenotypic plasticity with varying degrees of adaptedness to the test site conditions that prevailed in the analysed years. For reforestation and afforestation of similar habitats as was at the field trial it is recommended to use forest reproductive material from seed stands whose progeny expressed average to high phenotypic stability with a high degree of adaptedness (in terms of survival and height growth).
The results of this study should be considered as preliminary and stimulus for further research.

Key words: pedunculate oak; genetic test; adaptive genetic differentiation and diversity; phenotypic plasticity.

    authors:
    Popović, Maja  
    IVANKOVIĆ, Mladen    ŠL
    BOGDAN, Saša      ŠL
 
Ivana Vitasović Kosić, Mihaela Britvec  UDK 630*187 + 268 (001) 167
FLORISTIC AND VEGETATION CHARACTERISTIC OF FOREST EDGES AND GRASSLANDS OF ĆIĆARIJA (CROATIA)      
Summary
The aim of this study was to determine grassland flora (Tab. 2) and vegetation, and frequency of occurrence of woody and herbaceous species of the forest edge at different grassland management localities (Tab. 6, see Tab. 5). The field research of flora and grassland vegetation (2008–2010) was conducted at 27 localities (Tab. 1, Fig.1). A total of 103 relevés using the Braun-Blanquet (1964) method amounting to 100 m2 was made, while the description of habitats included geographical coordinates, altitude, inclination, exposure, land forms, and grassland management.
Woody species and herbaceous transgressive species from the Trifolio-Geranietea sanguinea class (according to Kaligarič 1997) were selected from the relevés (Vitasović Kosić 2011) and are hereinafter referred to as "herbaceous species of the forest edge". The presence and frequency of each taxon in relation to the type of grassland management were determined. For each taxon, Braun-Blanquet’s values were calculated as percentage of ground cover (%) on a particular grassland type and classified according to grassland management type. From a total of 103 relevés, 35 relevés were abandoned pastures (NP), 23 relevés abandoned meadows (NL), 20 relevés used pastures (KP) and 25 relevés used meadows (KL). The diversity of environmental grassland parameters and grassland management type was determined using modified Ellenberg indicator values (EIV) adjusted for the Mediterranean (Pignatti et al. 2005). The descriptive statistical analysis of environmental variables (Box & Whiskers diagrams) was conducted using the STATISTICA software package (StatSoft Inc. 2005).
A total of 624 plant taxa classified in 275 genera and 62 families was recorded whereas the top six families according to number of taxa (Asteraceae, Fabaceae, Poaceae, Lamiaceae, Liliaceae and Rosaceae) encompassed more than half (51.28 %) of the total recorded flora (Tab. 3).
According to phytogeographical analysis (Tab. 4), the nearly equal representation of the Mediterranean floral element (31.15 %) and Eurasian floral element (29.97 %) indicated that the studied area is located at the transition between the sub-Mediterranean and Mediterranean-mountain vegetation belt. Prevalent life forms include hemicryptophytes (53.83 %), which are typical for the grassland flora of pastures and meadows and indicate anthropogenic influence reflected in the form of grazing and burning. The relatively high prevalence of woody plants in the grassland habitats (N and P, 5.59 %) indicated processes of succession at some of the localities (Fig. 2).
The Ćićarija grasslands belong mostly to the Scorzonero-Chrysopogonetalia order (pastures) and partially to the Arrhenatheretalia order (meadows) (Poldini 1989, Kaligarič 1997, Poldini & Kaligarič 1997, Vitasović Kosić et al. 2011, 2012). A syntaxonomical interpretation of these associations is shown below.
From the total flora, 35 woody species (5.61 %) and 74 herbaceous species of the forest edge (11.86 %) from the class Trifolio-Geranietea sanguinei were singled out, indicating processes of vegetation succession at some of the localities (Tab. 5, Tab. 6). Among the endangered species, Gentiana symphyandra (EN) and the vulnerable Lilium bulbiferum (VU) should be noted.
According to grassland management, the largest number of woody and herbaceous species of the forest edge was detected within abandoned areas: NP – 58 taxa and NL – 28 species, while the used areas KL (16 taxa) and KP (7 species) contained significantly less.
The analysis of ecological indicator values (EIV) for woody and herbaceous species of forest edges (Fig. 3) showed that KP distinguished among the grassland management types, as can be seen by EIV nutrients, continentality, and light. Used pastures are generally homes to species that grow in poor soil nutrients (e.g., Genista sylvestris and Inula hirta), subcontinental (e.g., Asparagus tenuifolius), and continental species (e.g., Chamaecytisus hirsutus). As for the EIV of light, used pastures have more half-shade species, some of which cannot grow under full light (e.g., Helleborus multifidus subsp. istriacus). Contrary are used meadows where generally full-light species appear (Orobanche minor, Scabiosa columbaria, Rhinanthus aristatatus, etc.).
It is known that grassland management acts as a driving force in the diversity of the plant community (MacDonald et al. 2000, Kahmen et al. 2002, Wilson et al. 2003). During the last six decades, the abandonment of the traditional way of raising sheep resulted in different succession changes and significantly influenced biodiversity (Zupančić and Žagar 2002, de Bello et al. 2007). The main overgrowth of vegetation occurred in the contact zones between inadequately mowed and grazing plots. Other means of spreading woody species may include forest edges and shrub communities that occur as a phase in the very dynamic process of re-overgrowth, which most often has an anthropogenic origin (Čarni et al. 2002).Immediately after a plot ceases to be mowed or used for grazing, the occurrence of a high percentage of successional species is almost instant (Poldini 1989, Kaligarič & Poldini 1997, see Tab. 6). Due to the low usage intensity of grasslands, the colonizing grass Brachypodium rupestre spread across the entire plot (Catorci et al., 2011, 2012). In this study B. rupestre appeared at a large frequency (<40 %) on KL and KP, and with an even
greater frequency (>40 %) on NL and NP (see Tab. 5, compare Vitasović Kosić et al. 2012). The occurrence of B. rupestre in Ćićarija is consistent with several studies, all of which emphasize the role of B. pinnatum and B. rupestre in the invasion of unmanaged grasslands through processes of competition and related problems of conservation (During & Willems 1984, Bobbink & Willems 1987). According to Grime (1973, 2001), B. rupestre possesses dominant features such as large size, strong vegetative reproductive capacity (with marked lateral spreading), growth from basal meristems (Stebbins 1972), and high phytomass production (Catorci et al. 2012). Moreover, its silica-rich leaves render this species poorly palatable for sheep (Grime et al. 1988), thus enabling the formation of a large amount of plant litter and a consequent decrease in floristic diversity (Bonanomi and Allegrezza 2004; Bonanomi et al. 2009).
Under-grazing and irregular mowing (i.e., low disturbance) lead to the floristic homogenization of a system (Vitasović Kosić et al. 2011), which ultimately leads to a reduction in plant diversity. Meadows are subjected to the invasion of B. rupestre to a larger extent and, as stated by Bennie et al. (2006), they are more vulnerable to the loss of floristic diversity than pastures after regular management ceases. For this reason, regular mowing should be maintained and intensified. As for dry pastures, a solution for more efficient management could be in using very low selective herbivores, such as cows, donkeys or horses, for grazing.
In conclusion, particular attention in the protection and preservation of grasslands should be given to certain management measures (grazing and mowing) in order to maintain biodiversity, prevent grassland succession, and maintain control of the spread of B. rupestre. The results of this research can provide the basis for the development of new management plans, which will require specific knowledge on the preservation of biodiversity, particularly in Special Protected Areas (SPA) within the Natura 2000 network.
Syntaxonomical interpretation:
FESTUCO-BROMETEA Braun-Blanquet et R. Tüxen 1943
SCORZONERO-CHRYSOPOGONETALIA Horvatić et Horvat (1956) 1958
Saturejon subspicatae Horvatić 1975
                Carici humili-Centaureetum rupestris Horvat 1931
                aa) subas. satureetosum variegatae Poldini 1989 (= as. Saturejo subspicatae-Caricetum humilis Trinajstić /1981/1999, corr.2007)
                ab) subas. laserpitietosum sileris Kaligarič et Poldini 1997, variant with Laserpitium siler (so far observed only in Gorski Kotar)
                ac) subas. seslerietosum juncifoliae Horvat 1962 (= as. Seslerio juncifoliae-Caricetum humilis Horvat 1930)
Scorzonerion villosae Horvatić 1949
                Danthonio-Scorzoneretum villosae Horvatić (1956) 1958
                                subas. koelerietosum macranthae Vitasović Kosić 2011.
                Bromo-Chrysopogonetum grylli Horvat 1960
BROMETALIA ERECTI Braun-Blaunquet 1936
                Bromion erecti W. Koch 1926
                                Koelerio pyramidatae-Brachypodietum rupestris Trinajstić (1981) 2005
MOLINIO-ARRHENATHERETEA R. Tüxen 1937
ARRHENATHERETALIA Pawlowski 1928
                Arrhenaterion elatioris Braun-Blaunquet 1926
subas. Anthoxantho-Brometum erecti Poldini 1980 (= subas. Arrhenatheretum elatioris brometosum erecti Poldini 1989) – first time recorded in Croatia

Key words: grasslands; Scorzonero-Chrysopogonetalia; Brachypodium rupestre; woody species; herbaceous species of the forest edge; Ćićarija; Croatia

    authors:
    Vitasović Kosić, Ivana  
    Britvec, Mihaela  
 
 
PRETHODNO PRIOPĆENJE
 
Manana Kereselidze, Slavimira Draganova, Daniela Pilarska, Andreas Linde  UDK 630*453 185
SUSCEPTIBILITY OF Lymantria monacha AND L. dispar TO THE ENTOMOPATHOGENIC FUNGUS Isaria fumosorosea WIZE      
Summary
Isaria fumosorosea is a cosmopolitan fungal species with a large host range including insects which are economically important pests in agriculture and forestry. In the current study the susceptibility of two forest pests Lymantria monacha and L. dispar to an isolate of the fungus Isaria fumosorosea obtained from Hyphantria cunea and re-isolates from L. dispar, L. monacha and Dendrolimus pini was investigated under laboratory conditions. Newly molted third instar larvae of L. monacha and newly molted second, third and fourth instar larvae of L. dispar were inoculated with fungal conidia by various methods: Larvae of L. dispar were either dipped directly into the conidia suspension (1×108 conidia/ml), or indirect methods were applied – by surface contact of larvae with conidial suspensions (1×108, 1×109, 3×107, 3×108, or 4×108 conidia/ml) placed on filter paper discs in Petri dishes or by contact with oak leaves or larch needles dipped in conidia suspension. Larvae in control variants were treated with water. Mortality of larvae was checked daily for 20 days and the efficacy of the fungus was corrected with mortality in the control treatments. It was found that larvae of both Lymantria – species can be infected experimentally with Isaria fumosorosea. Similar corrected efficacy of Isaria fumosorosea for the third instars larvae of L. dispar (12.37 %) and for L. monacha (12.66 %) was found when 1x108 conidia/ml of the isolate from H. cunea was applied on filter paper. The highest corrected efficacy of Isaria fumosorosea for L. dispar larvae was 60.0 % when 1x109 conidia/ml of the isolate from H. cunea was applied on filter paper. A corrected efficacy of 27.85 % was recorded for L. monacha when 4x108 conidia/ml of re-isolate from L. dispar were applied on larch needles. Our results show that L. dispar and L. monacha larvae are within the psihological host range of the used Isaria fumosorosea isolate from H. cunea and re-isolates obtained from infected larvae of D. pini, L. monacha and L. dispar, however their susceptibility is low. Indirect treatment by surface contact of host larvae with fungal conidia caused higher efficacy of mycosis than dipping into the suspension.

Key words: Isaria fumosorosea; Lymantria monacha; Lymantria dispar; bioassays

    authors:
    Kereselidze, Manana  
    Draganova, Slavimira  
    Pilarska, Daniela  
    Linde, Andreas