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ŠUMARSKI LIST 3-4/2015 str. 70     <-- 70 -->        PDF

latency distances less than 200 m were not recommended, and in gradation they were generally arranged in groups spaced 50–100 m apart (up to 160 m apart in exceptional cases), but the spaces between pheromone traps within each group were not specified (Novák 1985). In Poland, the typical spacing between traps is approximately 15 m (Grodzki et al. 2008), while in Switzerland the recommended spacing between traps was 50 m (Maksymov and Kuhn 1984).
Other arrangements of traps have been tested but without ever being put into practice. For instance, Dubbel et al. (1985) spaced individual traps 2 m apart when evaluating the influence of trap colours. Weslien and Lindelöw (1989, 1990) used pipe traps in groups of 10–20 traps arranged in triangles with minimal spacing between them for the recapture of beetles. Vaupel and Dubbel (1985) used a single arrangement of 21 Theysohn slit traps placed closely together in a cross-like shape and with a single pheromone dispenser in the centre of the formation. The highest catch was registered in the centre, with a gradual decrease towards the outside of the formation. The central trap captured 15.1% of the beetles, those around the centre 8.43–14.39%, and those situated 3 m from the centre only captured 0.99–1.62%.
In all of these cases, the arrangements were made along the stand wall, either in groups or as individual pheromone traps. As stated previously, in most cases the results were not evaluated in relation to the types of trap arrangement.
Another type of arrangement is the setting of slit traps (Theysohn) in a star-like formation – three traps with one dispenser (Dimitri et al. 1986; Vaupel et al. 1986; Niemeyer 1987; Brutovský 1990; Zahradník 1997). All of these researchers saw increases in catches of 200% when compared to an individual Theysohn pheromone trap when using this arrangement with a single pheromone dispenser. Vaupel et al. (1986) also made an economic evaluation of this system, and the price ratio between the individual arrangement and the star-like arrangement of slit traps with one pheromone dispenser was 98:131.
At the turn of the millennium in areas with the gradation of I. typographus, testing began on the efficacy of pheromone traps installed in barriers along longer stand walls several hundred metres apart (Jakuš 1998; Jakuš and Šimko 2000; Jakuš and Blaženec 2003). The spacings between pheromone traps within the barriers were at a distance of 10–20 m (Jakuš 1998). Jakuš (2008) later installed triangular barriers (isosceles triangles with 12 m sides) of pheromone traps which made two lines of traps along each stand wall. Instead of comparing the efficacy of these arrangements against other types of set-up, these studies evaluated the resulting effect on the potential damage to other trees (number of infested trees). The safe distance from the stand wall was settled on as being at least 15 m (Dubbel et al. 1985; Novák 1984, 1985). Longer distances between the pheromone traps and the stand wall were rarely used, for example Jakuš (1998) placed traps 20–25 m from the stand wall.
The experimental approach in this research is based on the principles set out by the original Scandinavian researchers who placed the pheromone traps at the centre of a clear-cut area without making any comparison to the standard arrangement along the stand wall (references or parts of the above text). We did make this additional comparison and, at the same time, removed pheromone dispensers from some of the traps located in the centre of the clear-cut areas, similar to the way Vaupel et al. (1986) did in their star-like arrangement of Theysohn slit traps. However, unlike their study we did not evaluate the economic impact of such an arrangement.
This method may be particularly appropriate in locations after salvage felling or in clear-cut areas with a surface area of 1–2 ha or more (depending on the shape of the clear-cut area and likely to be more suitable for long rectangle-like or elongated clear cuts). Manipulation (setup) of pheromone traps in single locations, rather than long lines of traps as with the standard arrangement, can make the process quicker and therefore cheaper. The decreased number of dispensers can bring economic benefits, but is likely to result with decrease in the number of trapped beetles.
Conclusions
Zaključci
The statistical significancy of pheromone trap setup design was confirmed and with 95% statistical confidence it can be concluded that the set-up of pheromone traps affects bark beetle trapping. This is shown in the results from a calculated Fisher-Snedecor‘s criterion Fe = 30.185 which becomes higher than the critical value of the quantile of F1-0, 05 (4–1, 18–4) = 2.74.
There is no difference in the efficacy of traps when pheromone dispensers are installed in every other trap or in the middle/margin traps. Traditional set-up is considered to be equally efficient to traps installed closely without spaces between them and with a pheromone dispenser at each trap. This is confirmed by Scheffe‘s multiple comparison method which shows that the pairs of values A1 – A2 and A3 – A4 can be considered to be identical.
The greatest efficacy was provided by traditional set-up (A1) along a stand edge and in the middle of a clear-cut area with all traps baited (A2). With regard to difficulty of setup and its trappings the A2 setup seems to be optimal.
Aknowledgements
Zahvala
We would like to thank J. D. Fenton (U.K., London, edit@edthis.com) for language editing. This work was supported by the Ministry of Agriculture of the Czech Republic, project no. MZe 002070203 “Stabilization of forest functions in anthropogenically disturbed and changing environmental conditions”.