DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 1-2/2017 str. 54 <-- 54 --> PDF |
When the trap capture results were evaluated as 4 separate months (which are May, June, July and August), it was seen that the averages of June, July and August were not statistically different (p>0,05), mean while, the average for May was statistically different from other months (p<0,05) (Table 3). The average capture ratios for May is 6.32; 5.12 and 10.11 times higher than other months, respectively and according to this result, it is seen that spring captures are considerably higher than summer. In the study by Faccoli and Buffo (2004) for Ips typographus (Linnaeus), it was reported that spring captures are always higher than summer captures. Most bark beetle species’ population intensity tend to increase and decrease according to weather conditions and existence of the host in their natural living habitat (Raffa et al. 2015). Average temperatures in May, when the flights start, are between 10.55 and 14.77 ºC, average maximum temperatures are between 16.13 and 22.91 ºC. Daily maximum temperatures are sustainability to be important for the flight to begin and continue (Özcan et al., 2011). Gaylord et al. (2008), in the studies carried out various bark beetle species, has determined that maximum and average temperatures are more determinant than minimum temperatures in first flights. This determination supports the results of this study. Capturing more beetles in first flight period compared to second period may be due to traps capturing not only beetles in the effective region but also beetles coming from other regions (Jactel, 1991). Also, it is known that this species can fly 5-50 km distance and has the potential of easily going to farther distances where suitable hosts are available (Jactel and Gaillard 1991). It is believed that the population level of second generation is low due to many factors such as host trees being insufficient and climate conditions being unsuitable. 18 of the traps were placed at sunny and 12 at shaded aspects. The difference between the average number of I. sexdentatus captured in traps in sunny and shaded aspects is not statistically significant (p> 0.05). But, the number of beetles captured by traps in shaded aspects are 18.73% less than the sunny aspects (Table 4, Table 5). Özcan et al. (2011) has also found similar results. Also, Lobinger and Skatulla (1996) have reported that I. typographus was captured in higher rate in traps in south aspects than north aspects (Wermelinger, 2004). During the whole flight period of I. sexdentatus, a total of 576 T. formicarius adults were recorded in the traps. They were seen to be always present in the traps in all control dates. Predator insect was encountered mostly in the controls made during 22-29 May. The average amount of predators captured by the traps at this time are 2.3-5.2, respectively. One of the main predators of I. sexdentatus, Thanasimus formicarius L (Coleoptera: Cleridae) (Seedre, 2005), is a predator of many bark beetle species (Warzee and Grégoire, 2003). Also, this predator is attracted to bark beetle pheromones (Schoreder, 1997). Raffa et al. (2015) also suggests that stand structures are effective on the preferences of bark beetles. Accordingly, beetles that may cause severe tree deaths in one year by their outbreaks, can only cause deaths of live trees (Christiansen et al., 1987) when they cause an epidemic by increasing breeding potentials in other words, when their population reaches a level that exceed the resistance of the host (Drooz, 1985). In this study, it was identified that 19.65% of 458 trees evaluated in the sample plot covering 1.2 hectares of area were damaged by the beetle and accordingly, the damage rate in a hectare was 16.38% (Figure 4a, b), however, no |