Influence of Forest Type and Climate Factors on the Number of Caught Ips typographus (Coleoptera, Curculionidae) Bark Beetles in Pheromone Traps in Protected Areas of Bosnia and Herzegovina

As part of the research, the population of the eight-toothed spruce bark beetle in different types of forests in five protected areas in Bosnia and Herzegovina was analyzed. The study focused on the protected areas of Sarajevo Canton, specifically the secondary forests of fir and spruce, as well as the mixed forests of beech and fir (containing spruce). Pheromone traps were used as the research sample, and they were placed within PA Bijambara, PA Trebević, and PA Skakavac. The objective was to investigate the influence of forest type and climatological factors on the number of captured Ips typographus bark beetles from 2018 to 2021. The average number of captured I. typographus bark beetles during that period ranged from 491.39 to 901.68 individuals in secondary fir and spruce forests, and from 201.88 to 701.54 individuals in beech and fir forests (including spruce).

Currently, around the world, 19 million square kilometers, or approximately 12.5% of terrestrial areas are protected.In Bosnia and Herzegovina (BiH), this percentage is around 1.5% (Annonimus 2012) and protected forest areas cover an area of 18,232.30hectares, which is approximately 0.7% of the total area of BiH (Beus and Vojniković 2007).There are a total of 7 legally protected areas predominantly characterized by coniferous forests, with spruce (Picea abies (L.) H. Karst.)being the dominant species.It is known that various harmful abiotic and biotic factors can significantly affect the health of coniferous forests under certain conditions.The most common abiotic factors are climate and soil-related, while fungal diseases and bark beetles are the primary biotic factors.Bark beetles are of high ecological importance, as the majority of species live in dead or dying plants, thus being the early decomposers in forest ecosystems (Raffa et al. 2015).At the same time, bark beetles are perceived as forest pests that destroy and weaken trees (Gregoire et al. 2004, Raffa et al. 2015, Schebeck et al. 2023), where in specific conditions, like drought periods, they weaken the vitality of whole forests.In coniferous forests, bark beetles directly or indirectly can cause the drying out of more than 50% of trees (Wood 1982).One of the most well-known and dangerous pests for spruce with the potential to cause high economic losses in the forest ecosystems is the spruce bark beetle Ips typographus L. (Coleoptera, Curculionidae,

Influence of Forest Type and Climate Factors on the Number of Caught Ips typographus (Coleoptera, Curculionidae)
Bark Beetles in Pheromone Traps in Protected Areas of Bosnia and Herzegovina 2 SEEFOR 14(2): early view Scolytinae) (Wermelinger 2004).Although it is primarily considered as a secondary pest (Wermelinger 2004, Dautbašić et al. 2018, Netherer et al. 2019), in specific conditions it can build high population levels, killing huge numbers of trees in a short time.Such mass outbreaks are usually a consequence of different events like abiotic disturbances, such as wind-throw, snow-break or drought (de Groot et al. 2019), in forests where suitable material for wood production is being build.Climate change and extreme drought along with secondary attacks of bark beetles eventually lead to enlargement of population levels of bark beetles which then attack healthy trees.Such increase of bark beetle population in conifers is very well known and documented in European forestry (Hlasny et al. 2014, Nikolov et al. 2014, Dautbašić et al. 2018, Hlavkova et al. 2022, Hroššo et al. 2020, Vilardo et al. 2022).
In BiH I.typographus has two generations per year, with the first occurring in April and the second in July when a single female can deposit between 30 to 100 eggs.Mostly they attack the lower parts where the bark is thicker (Zahirović et al. 2016).Under favourable conditions, it can have a third generation as well.The attack lasts from April to September, after which it burrows under the bark and litter where it overwinters (Tomiczek et al. 2007, Zubrik et al. 2017, Dautbašić et al. 2018).Affected trees die very fast after exit holes appear.
The adult beetle of I. typographus is dark brown or black with punctured lines on its wing covers, and on each side of the elytra there are four teeth.It measures approximately 5.5 mm in length.The gallery system beneath the bark is created by the females during egglaying and by the larvae during their development, and it is usually one-or two-branched, occasionally threebranched.The length of the galleries depends on the intensity of the bark beetle attack, with shorter galleries indicating a stronger infestation and vice versa.The entire gallery system is located within the bark (Tomiczek et al. 2007, Zubrik et al. 2017, Dautbašić et al. 2018).Trees poses a defence mechanism, e.g.resin flow, and after bark beetles overcome and establish a mating chamber in the phloem they start releasing aggregation pheromones, attracting males and females (Francke et al. 1977, Byers et al. 1998).Syntheses for commercial production of the pheromone were developed in order to use the pheromones as bait in traps (Bakke 1983).Pheromone traps are primarily used for monitoring, although there have been attempts at pest control as well (Bakke et al. 1987).
Pheromone traps constitute a system composed of various housing designs that physically capture individuals and contain a chemical attractant -semiochemicals, to lure specific bark beetle species.There is a broad range of semiochemicals (Borden 1977), including pheromones that are released and received by individuals from the same species, and allelochemicals that mediate communication between species (Nordlund and Lewis 1976).The latter are further divided into kairomones, which are released by one species (e.g.host trees) and are to the benefit of the receiver of another species (e.g.bark beetles), allomones, which are beneficial for the emitter of another species, and synomones, which are to the benefit of both the sender and the receiver species (Nordlund and Lewis 1976).
The attractant Pheroprax has been developed for I. typographus and is widely used in forestry practices (Zuber and Benz 1992).This study aimed to determine the intensity of I. typographus infestation in different protected areas.The study investigated the influence of forest type and climatological factors on the number of caught I. typographus bark beetles.

Field Work
Out of 7 legally protected areas in Bosnia and Herzegovina (Annonimus 2016), five are located in the Sarajevo Canton: Vrelo Bosne (603 hectares), Skakavac (1,430 hectares), Bijambare (497 hectares), Trebević (400 hectares) and Bentbaša (160 hectares).The determination of catches of I. typographus within the protected areas of Sarajevo Canton was conducted over a four-year period between 2018 and 2021 and was carried out in Bijambare (44.09283,18.50049),Trebević (43.79736,18.48032),and Skakavac (43.94803,18.45249).For the catch of I. typographus Theysohn® pheromone traps and the Pheroprax® pheromone attractant (BASF Agro B.V Wadenswil, Switzerland) were used.The traps were positioned at a minimum distance of 20 m (± 2 m) from the nearest live coniferous trees.Counting the bark beetles and emptying the traps were carried out every 10-15 days.In the Bijambare protected area, 7 traps were installed during the period of 2018-2020, and 25 traps in 2021.In the Trebević protected area, 6 traps were installed during the period of 2018-2020.In the Skakavac protected area, 9 traps were installed in 2018, 6 traps in 2019, 14 traps in 2020, and 19 traps in 2021 (Figure 1).The traps were placed within two different types of forests: i) secondary forests of fir and spruce, and ii) mixed forests of beech and fir (with spruce).The analysis of trap catches was conducted at the laboratory of the Faculty of Forestry, University of Sarajevo.The distance between traps and healthy standing spruce trees was never under 20 m.

Laboratory Work
For measurement purposes, it was assumed that out of the collected bark beetles in 1 ml tube, there were 40 individuals of I. typographus (Hrašovec 1995).The accuracy of such assessment was tested on every twentieth sample, which showed a satisfactory level.The analysis of trap catches was conducted at the laboratory of the Faculty of Forestry, University of Sarajevo.The laboratory processing involved drying of the insects at room temperature and sorting the species under a microscope.The insects were first sorted by taxonomic categories and dried to facilitate counting.Based on the taxonomic categories, the insects were identified using available morphological keys (Pfeffer 1995).All larger insects, such as longhorn beetles, beetles with equally sized wings, and natural enemies were separated.

PA Bijambare
Counting of the sorted beetles in order to confirm the accuracy of the assessment was done manually.In this work we present only data for I. typographus.

Statistical Analysis
The analysis was conducted using the SPSS software (ver.20), and in addition to descriptive statistics, testing of the mean statistical significance (ANOVA) and Tukey HSD test were performed to determine the strength of the impact of forest type and climatological factors on the number of captured I. typographus individuals.

rEsULts
The study revealed that the average number of I. To analyse the impact of forest type on the number of captured I. typographus individuals, a test of statistical significance of mean differences was conducted.Table A1 presents the mean and standard deviation of bark beetle catches for the years 2018-2021 across different protected areas.
To determine the statistical significance of differences in bark beetle catches for the period 2018-2021 across   A2.
The statistical analysis conducted revealed statistically significant differences in the average catches of I. typographus bark beetles for the years 2018, 2020, and 2021 across different protected areas, at a probability level of p<0.05.However, no statistical significance was found in the average catches of I. typographus bark beetles for the year 2019 across different protected areas (Table A3).
According to the Tukey HSD test, a difference in the average catches of I. typographus was found in 2018 between the PA Bijambare and PA Trebević, and between PA Trebević and PA Skakavac.In 2019, no differences in the average catches of I. typographus were found.In 2020, a difference in the average catches of I. typographus was found between PA Bijambare and PA Trebević, and between PA Trebević and PA Skakavac.In 2021, a difference in the average catches of I. typographus was found between PA Bijambare, PA Trebević, and PA Skakavac.
Figures 6-9 depict the catches of I. typographus by month and by forest type for the period 2018-2021.
In order to analyse the effect of forest type on the number of captured individuals of I. typographus, a test of statistical significance was conducted to examine the differences in means.Table A4 presents the arithmetic mean and standard deviation of the catches of bark beetles for the years 2018-2021, according to different forest types.
To determine the statistical significance of differences in the catch of bark beetles for the period 2018-2021, depending on the forest type, a test of one-way analysis of variance (ANOVA) was conducted.The null hypothesis was set as follows: "There are no statistically significant differences in the average catches of I. typographus for the period 2018-2021, depending on the forest type, at a probability level of p<0.05."The results of the analysis are presented in Table A5.
The conducted statistical analysis determined that there are statistically significant differences in the average catches of I. typographus for the years 2020 and 2021, depending on the forest type, at a probability level of p<0.05.However, no statistical significance was found between the average catches of I. typographus for the years 2018 and 2019, depending on the forest type.
To determine the statistical significance of differences in the catch of bark beetles for the period 2018-2021, depending on climatological factors, a test of one-way analysis of variance (ANOVA) was conducted.The null hypothesis was set as follows: "There are no   The results of the analysis are presented in Tables A6-A9.
The conducted statistical analysis determined that there are no statistically significant differences in the average catches of I. typographus for the years 2018 and 2019, depending on climatological factors, at a probability level of p<0.05.However, statistical significance was found between the average catches of I. typographus for the year 2020, depending on the mean annual temperature and the maximum temperature of the warmest month.Statistical significance was also found between the average catches of I. typographus for the year 2021, for all parameters.

DIsCUssION
Despite available technologies, so far semiochemicalbased tools have been comparatively rarely used in agriculture and forestry, and conventional insecticides as the historically only alternative decreased in acceptance due to their environmental, social, and human health impact, so more sustainable alternatives are urgently needed (Pernek 2002, Gillette and Fettig 2021, Mafra-Neto et al. 2022).
This study encompassed the catch of I. typographus as an indicator of infestation in different protected areas of the Sarajevo Canton, as well as in different forest types.The focus of the research was to analyse the influence of year, forest type and climatological factors in the protected areas and forest type on the population abundance of I. typographus.The significance of this research lies in the analysis of the catch of I. typographus in different protected areas of the Sarajevo Canton, Bosnia and Herzegovina.The Pheroprax pheromone was used to determine the infestation intensity.The same pheromone was used for the catch of I. typographus by other researchers as well (Pernek 2002, Gillette and Fettig 2021, Mafra-Neto et al. 2022).Zahirović et al. (2016) found in their research that the average number of I. typographus caught on Theysohn® traps ranged from 2.04 to 966.41.The average number of I. typographus caught per trap in this study was significantly higher, reaching up to 2332.81 individuals, which can be partially attributed to the population outbreak of this bark beetle during the years of the research.
A one-way analysis of variance was performed to test the difference between the average catches of I. typographus depending on the protected area, revealing differences in the years 2018, 2020, and 2021.In 2018 and 2020, differences in catches were found between all protected areas, while in 2021, differences were found between PA Bijambare, PA Trebević, and PA Skakavac.One assumption for these results is that in all three protected areas, a higher number of traps were placed in secondary spruce and fir forests compared to beech and fir (with spruce) forests, resulting in higher catches of the bark beetle.

Secondary forests of fir and spruce
Mixed forests of beech and fir (with spruce)

Average number of caught
To determine the statistical significance of differences in bark beetle catches for the period 2018-2021, it was found that there are statistically significant differences in the average catches of I. typographus for 2020 and 2021, while no significant differences were found for 2018 and 2019, depending on the forest type.The study revealed that the catch of I. typographus was twice as high in secondary spruce and fir forests compared to beech and fir (with spruce) forests.One assumption for such a result is that there is a higher proportion of spruce trees in secondary spruce and fir forests, thereby providing a greater number of hosts for the bark beetle's development.
Studies have shown that non-host tree species diversity per se is not the main driver of outbreak risk, but that it strengthens biotic resistance with lower host availability at low altitudes where abiotic conditions are the least favorable to Norway spruce (de Groot et al. 2023).
Furthermore, the catch of bark beetles was investigated in relation to climatological factors, and for the years 2018 and 2019, no influence of climatological factors on the average bark beetle catch was determined.In 2020, the influence of the mean annual temperature and the maximum temperature of the warmest month on the average catch of I. typographus was determined.In 2021, the influence of the mean annual temperature, maximum temperature of the warmest month, minimum temperature of the coldest month, mean temperature of the wettest quarter, annual precipitation, and precipitation in the wettest and driest month on the average catch of I. typographus was determined.In his research, Faccoli (2009) also did not find an influence of precipitation during the activity period of I. typographus and the damage caused by this bark beetle throughout the year (Faccoli 2009).However, he found that increased damage occurred one year later if the precipitation was below the 10-year average.This leads us to the conclusion that precipitation, depending on climatic factors, directly and indirectly affects the population of I. typographus.Changes in climate factors can cause a sudden change in the behaviour of bark beetles, i.e. a sudden population growth (Pernek et al. 2019).
An appropriately established monitoring system makes it possible to take timely protective measures to prevent or reduce to the lowest possible level a more severe bark beetle infestation in protected areas.Timely detection of bark beetles gives companies managing protected areas sufficient space and time to respond in time to suppress bark beetle infestations.It should be remembered that the company managing protected areas in the territory of Sarajevo Canton does not have its own employees to perform the tasks of felling and exporting the felled trees, but third parties have to be contracted for these tasks.All this significantly slows down the process of rehabilitation of bark beetle infestation, which is why the monitoring system is the main line of defence when it comes to protecting forests from bark beetle infestation in protected forest areas.
In the future, further research will be needed on bark beetle catches in different protected areas, different forest types, and their relationship with various climatological factors in Bosnia and Herzegovina.

CONCLUsIONs
Based on the conducted research, the following conclusions can be drawn: The study analysed the catch of I. typographus in pheromone traps in the protected areas in Bosnia and Herzegovina with respect to different forest types and climatological factors.During the period of 2018-2021, the number of caught I. typographus where statistically significant among five studied protected areas.In the period of 2018-2021, a higher average number of caught I. typographus individuals were found in secondary forests of fir and spruce compared to beech and fir forests (with spruce).Statistically significant differences in the average catch of I. typographus were observed for the years 2020 and 2021, depending on the forest type, while no significant differences were found for 2018 and 2019.There were no statistically significant differences in the average catch of I. typographus bark beetles for the years 2018 and 2019 concerning climatological factors, while for 2020, statistical significance was found in relation to the mean annual temperature and maximum temperature of the warmest month.Additionally, for 2021, statistical significance was observed for all parameters.This work is important because it talks about the health condition of forests in protected areas, as well as the monitoring of harmful insects in them.Further research is needed on the catch of bark beetles in protected areas in Bosnia and Herzegovina.
8 SEEFOR 14(2): early view Appendix A typographus individuals in 2018 ranged from 0 to 371.43 (average 266.40) in PA Bijambare, from 0 to 2589.41 (average 1130.79) in PA Trebević, and from 0 to 677.78 (average 474.67) in PA Skakavac.In 2019, the average number of I. typographus individuals ranged from 0 to 2511.43 (average 778.57) in PA Bijambare, from 0 to 1748.89 (average 988.40) in PA Trebević, and from 0 to 1173.33 (average 592.38) in PA Skakavac.In 2020, the average number of I. typographus individuals ranged from 0 to 268.57(average 183.21) in PA Bijambare, from 64.44 to 1636.67 (average 758.98) in PA Trebević, and from 0 to 373.33 (average 238.19) in PA Skakavac.In 2021, the average number of I. typographus individuals ranged from 0 to 366.51 (average 205.67) in PA Bijambare, from 0 to 958.12 (average 784.62) in PA Trebević, and from 0 to 700.70 (average 484.87) in PA Skakavac.Within this study, a total of 80,470 individuals were caught in the Bijambare protected area, 346,880 individuals in the Trebević protected area, and 137,090 individuals in the Skakavac protected area.Figures 2-5 show the catch of I. typographus bark beetles by month for the period 2018-2021 in the respective protected areas.

Figure 6 .
Figure 6.Average number of caught I. typographus bark beetles in 2018.

Figure 7 .
Figure 7. Average number of caught I. typographus bark beetles in 2019.

Figure 9 .
Figure 9. Average number of caught I. typographus bark beetles in 2021.

number of caught Month Average number of caught Month Figure 4.
Average number of caught I. typographus bark beetles in 2020.There are no statistically significant differences in the average catches of I. typographus bark beetles for the period 2018-2021 across different protected areas at a probability of p<0.05."The results of the analysis are presented in Table Month Figure 3. Average number of caught I. typographus bark beetles in 2019.Figure 5. Average number of caught I. typographus bark beetles in 2021.

Month Month Average number of caught Average number of caught
6 SEEFOR 14(2): early view statistically significant differences in the average catches of I. typographus for the period 2018-2021, depending on climatological factors, at a probability level of p<0.05."

Table A1 .
Arithmetic mean and standard deviation for I. typographus catches from the period 2018 -2021 for different protected areas.

Table A2 .
Analysis of variance (ANOVA) of statistically significant differences in I. typographus catches depending on the protected area.

Table A4 .
Arithmetic mean and standard deviation for the catch of I. typographus bark beetle from the period 2018 -2021 for different forest types.

Table A3 .
Multiple tests of average differences in the catch of I. typographus bark beetles for 2018, 2019, 2020 and 2021 depending on the protected area (Tukey HSD).The differences in the catches of I. typographus depending on the protected area are highly statistically significant at a probability of 0.05.

Table A5 .
Analysis of variance (ANOVA) of statistically significant differences in I. typographus catches depending on forest type.

Table A6 .
Analysis of variance (ANOVA) of statistically significant differences in I. typographus catches depending on climatological factors in 2018.

Table A7 .
Analysis of variance (ANOVA) of statistically significant differences in I. typographus catches depending on climatological factors in 2019.

Table A8 .
Analysis of variance (ANOVA) of statistically significant differences in I. typographus catches depending on climatological factors in 2020.