RESEARCH CARRIED OUT IN ON THE NORTHERN BARK (IPS DUPLICATUS, COLEOPTERA: , SCOLYTINAE)

Mihai-Leonard DUDUMAN, „Ştefan cel Mare” University of , Forestry Faculty Nicolai OLENICI, Forest Research and Management Institute, Experimental Station for Spruce Silviculture, Câmpulung Moldovenesc Gabriela ISAIA, „Transilvania” University of Braşov, Faculty of Silviculture and Forest Engineering.

Abstract: The northern bark beetle, Ips duplicatus (Sahlberg, 1836), native from Eurasian boreal forests, is an invasive species in Central and Southeast Europe and mainly occurs in the spruce stands located at altitudes below 1000 m a.s.l. It develops outbreaks especially within areas where spruce was cultivated outside of its natural range. The faunistic records of this species started in 1948 in north- eastern part of Eastern Carpathians (Rarău Mountains). Until 1970, this species was faunistically reported from Eastern Carpathians and eastern part of Southern Carpathians. In 2011 the presence of the species was recorded in the most areas where spruce is growing, excepting the Mountains and the areas exceeding 1000 m altitude. Its first outbreak began in 2004-2005 and is still in progress mainly in spruce stands of 35–45 years old, but also in older ones, in hilly zone from north-eastern part of Romania. The vulnerability of the stands where outbreaks occurred increased due to their high density, drought and less favorable soil conditions (pseudogleyzation) in some cases. Regarding the ecology of this species, the research was focused mainly on phenological and chemoecological aspects. Thus, studying the seasonal flight activity of Ips duplicatus versus Ips typographus in different elevation conditions, it was found that Ips duplicatus starts the flight a few days earlier than Ips typographus and, at least in the hilly areas of north-eastern Romania, these species develop two complete generations per year. The chemoecological research was focused on the study of olfactory behaviour of Ips duplicatus adults. It was observed that the bark concentrate on areas with large amounts of fresh spruce debris which release high quantities of specific volatile substances (terpenes and alcohols). The research continues at this time to identify the effects of some monoterpenes from spruce oleoresin (alpha-pinene and limonene), on olfactory behavior of Ips duplicatus bark beetles attracted by synthetic pheromones.

Key words: Ips duplicatus, research development, Romania.

1. INTRODUCTION

The northern spruce bark beetle Ips duplicatus (Coleoptera: Curculionidae, Scolytinae) (Sahlberg, 1836) is, as the name implies, a characteristic species of the Eurasian boreal coniferous forests, being native met from Scandinavia to the Siberian Taiga and Sachalin Island, but isolated in the Austrian Alps (Pfeffer, 1995, Wood and Bright, 1992). The extension of this species areal to Central and Southeast Europe was noted in faunistic records from the early part of the 20th century. Thus, Hagedorn (1910) speaks about the presence of Ips duplicatus at that time, except for Finland and Russia, in the Upper Silesia (South-West of Poland). Subsequently, the species was found in Steiermark Region (Southeast of Austria) and in Świdnica – Lower Silesia (West of Poland) (Reitter, 1916), and in 1920 was reported from Luboreč (South of Slovakia) (Roubal 1937-41 cited by Zúbrik et al., 2006). After 1920, this species was repeatedly collected in the Czech part of Silesia (Wanka, 1927; Pfeffer, 1955, cited by Knižec et al., 2006). In the 1970s it became a common species of spruce stands located at altitudes below 1000 m a.s.l. 9 in Slovakia and Czech Republic (Zúbrik et al., 2006; Mrkva, 1994; Holuša and Knižek, 2007), in Poland being frequently found in coniferous stands located in the Southwest of Sudetes Mountains and in Northern Carpathians, also at elevations which do not exceed 1000 m a.s.l. (Holuša and Grodzki, 2008). The expansion to the west and southeast Europe of this species area was confirmed by records from Germany, Belgium, France, Hungary, the former Yugoslavia, Romania, Bulgaria, etc. (EPPO/CABI, 1996). In Asia, important populations of Ips duplicatus have been reported in Inner Mongolia (China) (Zhang et al., 1995), and some specimens have found in Japan (Honshu Island) (EPPO/CABI, 1996). Ips duplicatus prefers as hosts various species of spruce (Picea abies, P. obovata, P. mongolica), but it can also be found on different species of pine (Pinus sylvestris, P. sibirica, P. strobus) or larch (Larix sibirica) (Schedl, 1981; Pfeffer, 1995; Zhang et al., 1995; Holuša and Grodzki, 2008; Postner, 1974), and according to some authors, even on species of Abies and Juniperus (Stark, 1952; Mrkva, 1994; 1995). This bark beetle prefers weakened trees of 40-70 years, located in sunny places at the forest edges or within thinned stands, and colonizes mainly the upper third of the stem (Stark, 1952; Pfeffer, 1955; Postner, 1974; Bakke, 1975). It avoids the trees which were cut down or it colonizes them only slightly (Bakke, 1975; Lekander el al., 1977). The outbreaks of Ips duplicatus in its native range (boreal zone) are tightly correlated with those of Ips typographus, and are caused by the accumulation of large quantities of favorable host material resulting from the wind felled trees (Bake, 1975). Only rarely happens that Ips duplicatus is more abundant than Ips typographus (Voolma, 2005). However, in areas where the northern bark beetle has extended its range during the last hundred years (Central Europe and Inner Mongolia – China), it was able to develop local outbreaks, especially after the 1950 in China and after 1990 in Central Europe (Zhang et al., 1995; Hrubrik, 2007; Holuša and Knižec, 2006; Grodzki, 2003; Prizybyl et al., 2008; Olenici et al., 2009, 2011). These outbreaks occurred within heavily debilitated spruce stands after combined action of various abiotic and biotic factors. Most of those stands were established on improper sites for spruce species, frequently affected by summer drought and very high temperatures, or by fire, wood decay fungi, defoliator , etc. (Zhang et al., 1995, Holuša, 2001; Knižec, 2001; Stanovský, 2002; Knižec et al., 2006; Prizybyl et al., 2008; Olenici et al., 2009, 2011). The southward enlargement of species area and the problems caused by its outbreaks in the new territories qualify Ips duplicatus as an invasive species in the most countries in Central, West and South Europe (Vakula et al., 2007; Zúbrik et al., 2007; DAISIE, 2009; Sauvard et al., 2010). The occurrence of Ips duplicatus in Romania was proved by records from the years 1948-1953 (Negru and Ceianu, 1957), but the interest for this species remained very low until 2008, when it was found that this species is the main actor in a bark beetle outbreak (Olenici et al., 2009). This fact has stimulated the interest for Ips duplicatus, and studies concerning its distribution in Romania, outbreak evolution, phenological and ecological aspects have been undertaken.

2. IPS DUPLICATUS IN ROMANIA

2.1. Records of the Ips duplicatus

In Romania, the presence of Ips duplicatus was discovered for the first time in 1948, in the northern part of the Eastern Carpathians (Rarău Mountains, ), when 9 beetle (3 males and 6 females) were found under bark of infested spruce, together with Ips typographus (Negru and Ceianu, 1957). The subsequent records, until 1953, were from different locations along the Bistriţa River (1949: Secu-Taşca, Galu, Bicaz, Buhalniţa, Tarcău, Tazlău - Neamţ County), as well as in locations near that of the first record (1951: Lucina and Câmpulung Moldovenesc; 1953: Câmpulung Moldovenesc – Suceava County), or from distant, isolated points as the Dendrological Park Roznov (Neamţ County) and Hemeiuşi Park (Bacău County) (Negru and Ceianu, 1957). Since 1962 appeared new records of Ips duplicatus from areas where the presence had been testified (Suceava County - 1965: Vama, Iacobeni; Neamţ County - 1962: Roznov, 1965: Piatra Neamţ, 1967: Bicaz), but also from new locations, mostly situated on western or southern part of the Eastern Carpathians (Maramureş County – 1965: Dragomireşti, Târgu Lăpuş; – 1965: Topliţa, Sînmartin; Mureş County – 1965: Lunca 10

Bradului; – 1965: Baraolt; Buzău County – 1965: Nehoiu; – 1965 – Mîneciu) or in a isolated location in Southern Carpathians (Vâlcea County – 1965: Voineasa) (Vasiliu et al., 1978). In the most faunistic records from the years 1948-1967, Ips duplicatus is mentioned on infested Norway spruce trees, usually along with Ips typographus and Ips amitinus, and less often together with Pityogenes chalcographus, laricis, Dryocoetes autographus. This bark beetle has been found also on trees of Scots pine (at Tarcău – 1949, Lucina – 1951, Roznov – 1962) and Pinus strobus (at Roznov, 1952) (Negru and Ceianu, 1957; Vasiliu et al., 1978). New records for Ips duplicatus have been reported since 2008. Thus, beetles of this species have been found in captures obtained with pheromone traps for Ips typographus set up in several locations of the mountain area of Suceava County (2008: Paltinu – Ionu; 2010: Giumalău). It has also been collected from under the bark of many infested trees in pure spruce stands growing outside the natural range of this tree species, in the hilly zone of Suceava County (Calafindeşti, , Feteşti, Fălticeni, ) (Olenici et al., 2009; Duduman et al., 2011a). In the years 2010-2011 there have been some observations on the presence of Ips duplicatus both in the areas where it had been already reported as well as in other areas of Romania, where this species was expected to be present. Thus, Duduman et al. (2011b) have verified the presence of the species in thirty-five representative locations using pheromone traps (Intercept® type) baited with specific pheromones of Ips duplicatus (ID Ecolure from Slovakia). These were installed in the proximity (10-12 m distance) of the spruce stands that are located at elevation between 200 and 1200 m a.s.l., and aged 35–115 years. Ips duplicatus occurrence was noted in new locations from all areas where it has been reported before: Suceava County - Giumalău, Ionu, , Zamostea, Calafindeşti, Feteşti; Neamţ County - Bolovăniş, Brateş, Aţa, Valea Uzului; Bacău County - Valea Uzului; Harghita County - Răchitiş; Covasna County - Breţcu; Mureş County - Filipişu Mare; Maramureş County - Mare, Tăuţii Măgheruş, but also in other new areas like Botoşani County - Flămânzi, Bahlui; Iaşi County - Tătăruşi; - Ivăneşti; Braşov County - Tărlungeni, Poiana Braşov, Râşnov, Tohanu Vechi; - Tălmăcel; – Sibişel. The traps installed in (Scânteia), Buzău County (Gura Teghii), Argeş County (Berevoieşti) and Caraş (Izvoarele Nerei) did not capture any Ips duplicatus beetle. In summary, it can be stated that in Romania Ips duplicatus is present in almost all area of Norway spruce (except Banat Mountains), situated at elevation bellow 1000 m a.s.l. (Duduman et al., 2011b).

2.2. Ips duplicatus outbreak in Romania

The first outbreak of Ips duplicatus in Romania was noted in 2008 (Olenici et al., 2009) and it was located in spruce stands of 30-50 years, installed outside of the natural range of spruce in the northeastern part of Romania, namely in the hilly zone of Suceava County (Forest Districts Adâncata, Pătrăuţi, Fălticeni, Dolhasca). Analysing the foci developed in these stands, it was found that Ips duplicatus was the dominant species in the bark beetle assemblages, the other main species attacking the trees being Ips typographus, Pityogenes chalcographus, Polygraphus poligraphus, Pityophthorus pityographus (Olenici et al., 2011). The beginning year of the outbreak was established using chronological data for the number of bark beetle infested trees in spruce stands growing outside of the natural range since 1995 to 2009. Thus, the number of attacked trees significantly increased after 2002- 2004, reaching a level of 50,000 infested trees per year in 2007-2009 (Olenici et al., 2011). In August 2012 there were already reported over 100,000 trees infested during the current growing season. At the same time, it was noted that the Ips duplicatus outbreak covered artificial spruce stands from Botoşani and Iaşi counties, as well as some spruce stands situated at the lower altitudinal limit of the spruce natural range, in the premountain zone of Suceava County (Forest Districts , Putna, , , , Mălini and Râşca).

2.3. Factors that favoured the development of Ips duplicatus outbreak

Research carried out by Olenici et al. (2011) have demonstrated that the Ips duplicatus outbreak in northeastern part of Romania has occurred in severe debilitated spruce stands from outside of this species natural range, after the increase of bark beetle population since 2002. Population increase is most 11 likely due to the introduction into the hilly area of significant quantities of infested wood from the mountain area (located about 50 km away) in the years after the huge windfall that occurred in Suceava county in March 2002 (Simionescu et al., 2007). The debilitation of those spruce stands was due to the common action of several factors, including severe droughts in the years 1986-1987, 1990, 1992, 1995- 1996, 2000-2004 and 2007, whose effects were revealed by the analysis of the tree radial growth, or Pristiphora abietina attacks which started in the years 1993-1994 and continued every year with varying intensities. The strongest Ips duplicatus foci have developed in the most debilitated spruce stands. They were typically very dense stands (2,000–3,200 trees per hectare), installed in less favourable soil conditions (pseudogleyzation) (Olenici et al., 2011). The development of Ips duplicatus outbreaks in Romania has occurred in conditions similar to those of the outbreaks recorded in Central Europe (Stanovský, 2002; Grodzki, 2003; Holuša & Knižec, 2006; Hrubrik, 2007).

2.4. Ecology of Ips duplicatus

Phenological studies about the flight activity of Ips duplicatus versus Ips typographus, conducted in different elevation conditions, using pheromone traps baited with the specific pheromones, showed that, at least in 2010, Ips duplicatus started the flight activity in spring earlier than Ips typographus, and that both species developed two complete generation per season at low altitudes (Zamostea, 375 m) (Duduman et al., 2011a). The monitoring of the flight activity and insect development under the bark of infested trees in Suceava hilly area (Zamostea, Calafindeşti and Feteşti) during the growing season in 2011 has confirmed that Ips duplicatus develops two generations per year in this zone, and that flight activity dynamics has three maxima, by the end of April, end of June – beginning of July, end of August – beginning of September. The chemoecological researches were started with the study of influence of spruce natural volatiles released by fresh debris on Ips duplicatus response to the characteristic synthetic pheromones. We found that in pheromone traps installed within the areas with important quantities of fresh spruce debris there were captured significantly larger numbers of Ips duplicatus beetles than in the traps installed within the areas where no debris were present, concluding that the beetles were concentrated (as with other species of bark beetles) within the areas with large amounts of specific natural volatiles (terpenes and alcohols) from spruce (Duduman and Vasian, 2012). Currently, there are in progress researches on identifying the effect of some monoterpenes from spruce oleoresin ((–)alpha-pinen and (+)limonene) on the olfactory response of Ips duplicatus beetles to the characteristic synthetic pheromones. Preliminary results indicate that the response to pheromones (pheromone blend release rate of 23 mg/day) is intensified as the release rates of (–)alpha-pinen and (+)limonene increase from 50 to 1000 mg/day (Duduman, 2012).

3. CONCLUSIONS

Although Ips duplicatus was recorded in Romania since 1948, and in the meantime extended its territory in almost all area of Norway spruce, except Banat Mountains and mountain zone above 1000 m a.s.l., this species has not attracted significant attention until 2008, when the first outbreak got underway in spruce stands installed outside of the natural range in the hilly zone of northeastern part of Romania. Before 2008, the research conducted on this species in Romania had mostly a faunistical character. After 2008, the research, focused especially on aspects related to the development of Ips duplicatus outbreak, but also on aspects of the ecology of this species (phenology, chemoecology).

ACKNOWLEDGEMENTS

This work was supported by „The National Authority for Scientific Research” CNCSIS- UEFISCSU, PN II-RU 576/2010 – „Role of the Norway Spruce volatile substances upon Ips 12 typographus and Ips duplicatus bark beetles response to aggregative pheromones”, contract number 204/2010 and MOTIVE Project–Models for Adaptive Forest Management, funded by 7th EU Framework Programme.

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