RESEARCH CARRIED OUT IN ROMANIA ON THE NORTHERN BARK BEETLE (IPS DUPLICATUS, COLEOPTERA: CURCULIONIDAE, SCOLYTINAE) Mihai-Leonard DUDUMAN, „Ştefan cel Mare” University of Suceava, 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 Banat 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 beetles 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 insects, 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, Suceava County), 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 insect 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; Harghita County – 1965: Topliţa, Sînmartin; Mureş County – 1965: Lunca 10 Bradului; Covasna County – 1965: Baraolt; Buzău County – 1965: Nehoiu; Prahova County – 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, Orthotomicus 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, Zamostea, Feteşti, Fălticeni, Dolhasca) (Olenici et al., 2009; Duduman et al., 2011a). In the years 2010-2011