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The ecology of I. cembrae differs in some details from that of other Ips species (Postner 1974). The ecology and control of this beetle in central Europe, however, has been the subject of only a few recent studies (Hutka 2006, Grodzki 2008, Grodzki and Kosibowicz 2009).
The aim of the research described in this report was to define: the period of I. cembrae flight activity in central Europe; the distribution of I. cembrae in time and space on trap trees; and the I. cembrae overwintering locations.
Materials and methods
Materijal i metode rada
the research was carried out near the villages of SlezskÚ Rudoltice (50░12ĺ37.827öN, 17░38ĺ52.579öE) (2007ľ2008) and at ┌týchov (49░17ĺ12.646öN, 16░37ĺ15.632öE) (2008ľ2009) in the eastern Czech Republic. At the SlezskÚ Rudoltice locality, we selected a 1.55-ha forest stand that was 56 years old and had a closed canopy; the larch, which represented 90% of the trees in the SlezskÚ Rudoltice stand, had an average d1.3 of 23 cm and an average height of 23 m. At the ┌týchov locality, we selected a 7.02-ha forest stand that was 88 years old and had a closed canopy; the larch, which represented 44% of the trees in the ┌týchov stand, had an average d1.3 of 29 cm and an average height of 27 m.
At SlezskÚ Rudoltice, the seasonal period of I. cembrae flight activity was determined by trapping beetles using Theysohn« slot barrier traps and Cembrńwit« lures. Five traps were placed 10 m apart along the stand edge in 2007 and 2008. Lures were added to traps in mid-April, just before the beginning of emergence, and were renewed 8 weeks later. The traps were inspected every 7ľ10 days from mid-April until the end of August in both years.
Six sets of trap trees (three sets at each locality) were used to estimate changes in I. cembrae abundance in wood from spring to summer. Each trap tree was a healthy larch that was cut about 0.5 m above the soil and left in place on the soil surface. Sets 1şľ3 were in the SlezskÚ Rudoltice stand and were deployed from April to June in 2007 (seven trap trees), from April to June in 2008 (eight trap trees), and from July to August in 2008 (five trap trees). Sets 4ľ6 were in the ┌týchov stand and were deployed from April to June in 2008 (three trap trees), from April to June in 2009 (three trap trees), and from July to August in 2009 (three trap trees). The trap trees were 10ľ15 m apart and were located along the edge of the stand if cut late in March (sets 1, 2, 4, and 5) and within the stand if cut late in June (sets 3 and 6). Four sections were designated on each trap tree according to the method of Grodzki (2004). The first section (bottom) was located from 0.0 to 0.5 m from the bottom of the tree; the second section (stem) was located midway between the bottom section and the beginning of the crown; the third section (middle) was located at the beginning of the crown; and the fourth section (crown) was located in the centre of the crown. Change in I. cembrae abundance was determined by counting the number of entry holes every 7 to 10 days in one strip (0.1 Î 1.0 m) on the upper part of each section. Each entry hole was marked with a pin to facilitate counting.
We determined how position in the trap tree affected oviposition and larval development. For the four sections of each of three traps trees at ┌týchov in 2008, we determined the number of galleries, the length of maternal galleries, the length of the 10 longest larval galleries, and the numbers of larval galleries.
To determine whether I. cembrae completed development and overwintered in trap trees, five 0.7-m-long logs (Σ 20) were cut from the upper part of each of four trees at SlezskÚ Rudoltice in August 2008 and were left in place until they were moved to the laboratory.. At the end of September, October, November, and December 2008, and of January 2009, four logs (one from each tree) were placed in emergence traps in the laboratory (20 ░C, 16 h of light and 8 h of dark); emergence was assessed every 14 days until the end of March 2009.
To determine whether I. cembrae completed development and overwintered in the forest litter, 10 emergence traps (each covering an area of 0.5 m2) were placed in pairs on the litter near the base of each of five trap trees at SlezskÚ Rudoltice at the end of March 2009; the pairs of traps were 10 m apart, and the number of beetles in the traps was assessed every 14 days until the end of June 2009.
Numbers of entry holes and number of beetles trapped were compared with nonparametric tests (Mann-Whitney U test, Kruskal-Wallis test, median test) performed with Statistica 9.0.
Period of flight activity
A total of 18,258 beetles were captured in the five pheromone traps at SlezskÚ Rudoltice in 2007 and 2008. Flight activity began in the second half of April and ended at the beginning of August (Figure 2). Significantly more beetles were trapped in 2007 than in 2008 (U=1075.5**).
Seasonal increase in abundance in infested wood
The number of entry holes on trap trees at SlezskÚ Rudoltice dropped significantly from spring 2007 to summer 2008 (H[2, N=92] = 57,48****; Table 1). At ┌týchov, the number of entry holes on trap trees increased significantly from spring 2008 to summer 2009 (H [5, N=152] =94.26***; Table 1).