DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
| ŠUMARSKI LIST 3-4/2015 str. 69 <-- 69 --> PDF |
Results Rezultati The location factor was found to be statistically insignificant so the localities were considered to be identical in the following assessment. The significance of factor A (system of pheromone traps set-up) using an analysis of variance was examined fist. The count Fisher-Snedecor test criteria Fe = 30, 185 is higher than the critical value of fractile F1–0,05(4–1, 18–4) = 2,74, confirming the alternative hypothesis on the significance of the set-up system effect. The system of set-up is statistically significant with a probability of 3,408E–021. A more detailed focus is provided by the pair test which compares each system against another (Table 1). There was no statistical significance in the differences between the traditional system (A1) and system with every baited trap (A2) and also statistically insignificant is the difference between the system with every second trap baited (A3) and the middle and margin traps baited (A4). All of the other comparisons were statistically significant. The traditional A1 system was chosen as the standard for efficacy evaluations as percentages, i.e. 100 % (Figure 2, Table 2). In 2009 no other system showed greater efficacy (A2 91 %, A3 61 %, A4 51 %,). Although A2 showed an efficacy of 140 % in 2010, it was only 79 % for A3 and 64 % for A4. Discussion Rasprava As early as the first use of pheromone traps in Norway and Sweden at the end of the 1970s, traps have been placed along a stand wall after storms and subsequent bark beetle outbreaks. In Norwayinstalled drainpipe traps – types Borregaard 1979 and Borregaard 1980 (with funnels connected to collecting containers on the bottom part of the trap) in groups of 3–8 traps spaced 5 metres apart at a distance of 30 metres from the stand wall (Bakke and Strand 1981). In Sweden, drainpipe traps were placed in groups of 12–15 spaced 2–10 metres apart (Regnander and Solbreck 1981). In Sweden initially, single traps were generally used but the placement of traps in groups proved more effective (Eidmann 1983). Pheromone traps were used in an extensive gradation; average catches in pheromone traps during the flight activity each season ranged from 7 to 20 thousand and even more in some areas. There were already attempts at that time to determine the optimum placement of pheromone traps. Bakke at al. (1983) tested the efficacy of six hexagonally arranged drainpipe traps with spaces of 0,5 m, 1,5 m, 3 m, 6 m and 12 m between the traps in each group. No significant differences between catches were found. They also tested the placement of 91 pheromone traps arranged hexagonally and spaced 20 m apart in a large, clear-cut area. Catches in individual traps rarely exceeded 1000 beetles and were less than 500 beetles per season in approximately half of the traps. Later, Bakke (1985) also tested groups of 3 drainpipe traps arranged in a triangle and spaced 5 m apart. Similarly, Niemeyer and Watzek (1982) used groups of 3 pheromone traps (various types) spaced 5 m apart from each other and at a distance of 60 m between the groups of traps. The number of catches in the pheromone traps was not considered to be the key criteria, rather their evaluation was based on the comparison of the initial number of infested trees and the number of installed pheromone traps in the given area, and then the subsequent number of newly damaged trees in the following year. These results are likely to have contributed to the more common use of varying spacing for the placement of pheromone traps along stand walls. The actual distance between traps depends on the population density of beetles: in |