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The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae) is one of the most important insect pests in deciduous forests of the Palaearctic zoogeographical zone and in northeastern North America where it was accidentally introduced in 1869. The preferred food plants of this polyphagous species are oaks (Quercus spp.). An outbreak species, gypsy moth defoliates large areas of oak forests, primarily in southeast Europe and sandy ridges in the US Appalachian Mountain chain, as well as the more recently invaded areas of North America (McManus and Csóka 2007).
Entomophaga maimaiga Humber, Shimazu and Soper (Entomophtorales: Entomophtoraceae) was described as host specific pathogen of Lymantria dispar japonensis Motschulsky in Japan where it causes epizootics (Shimazu and Soper 1986; Soper et al. 1988). Epizootics were also reported in South Korea, Pacific region of China, Sakhalin Islands, India, and the Primorsky region of far-eastern Russia, as well as from Poland and Yugoslavia (Hajek 1999).
E. maimaiga was first introduced into USA in 1910–1911 and 1985–1986 with inocula from Japan. Both introductions were reported as unsuccessful (Hajek et al. 2005); however, in 1989, the pathogen was reported causing epizootics in gypsy moth populations in seven northeastern US states (Andreadis and Weseloh 1990; Hajek 1999). Andreadis and Weseloh (1990) suggested that E. maimaiga may have survived via resting spores and spread through the North American gypsy moth population, and the ability of the pathogen to spread rapidly suggests that the fungus was probably accidentally introduced into the US prior to its detection in 1989 (Hajek 1999; Nielsen et al. 2005). E. maimaiga has expanded its range by natural distribution and introductions in L. dispar populations in North America (Solter and Hajek 2009).
In 1999–2000 E. maimaiga was successfully introduced in two gypsy moth populations in Bulgaria via inoculum from the US (Pilarska et al. 2000). Several years later, in forest stands situated at considerable distances from the introduction sites, the first important epizootics of the pathogen were recorded (Pilarska et al. 2006). For a period of 10–12 years, E. maimaiga expanded its range (naturally and by introductions) and is now found throughout Bulgaria (Georgiev et al. 2011). Proximity of sites where epizootics have occurred to neighbouring countries suggests that the pathogen probably has spread beyond the borders of Bulgaria (Georgiev et al. 2010). In 2011, E. maimaiga was found in the European part of Turkey (Georgiev et al. 2012a) and in Central Serbia (Tabaković-Tošić et al. 2012).
E. maimaiga is an extremely effective gypsy moth pathogen where epizootics have occurred. After the fungal epizootics in US in 1989, gypsy moth management programs were discontinued in some states. For example, in central New York State, there have been no outbreaks of gypsy moth since 1992 (Hajek 1997; Kereselidze et al. 2011). In Bulgaria, after the introduction of E. maimaiga, the most recent outbreak of L. dispar (2001–2009) included 108,000 ha, approximately 10–20% of the area typical of previous pest infestations, 492,000–1,028,000 ha (Georgiev et al. 2011).
In this study, we report on the first record of E. maimaiga in Greece and the Former Yugoslavian Republic of Macedonia (hereafter, FYROM). The observation of the fungus in both countries was only mentioned at the International Scientific Conference "Forests in Future-Sustainable Use, Risks and Challenges" held in Serbia in 2012 (Georgiev et al. 2012b), however no information about pathogen occurrence nor its prevalence in the gypsy moth populations studied has yet been presented.
Material and Methods
Materijali i metode
The studies were conducted during the spring of 2012. Different oak stands were visited and studied in Greece and FYROM but gypsy moth larvae were observed and collected only in three localities in the region of Xanthi (Greece) and in three sites in the region of Prilep (FYROM). Detailed site data are presented in Table 1.
The study sites in Greece consisted of mixed stands of Quercus frainetto Ten., Quercus cerris L. and Quercus petraea (Matt.) Liebl. In two sites in FYROM, Toplica and Belovodica vill., Macedonian endemic oak, Quercus trojana Webb dominated, and in the third site (Krushevo vill.), Q. cerris was dominant.
Collections of gypsy moth larvae were made from leaves in the lower parts of tree crowns. The age structure of gypsy moth larval population was determined by the width of epicranium. Methods for larval rearing and microscopic analyses of dead larvae were used as described in previous studies (Pilarska et al. 2006; Georgiev et al. 2011; Georgiev et al. 2012a).
Studies in Greece – Istraživanja u Grčkoj
Sixty three and 77 gypsy moth larvae were collected on May 18 and May 31, respectively (Table 1). Gypsy moth larval stages ranged from second to fifth instar on May 18, and from second to sixth instar on May 31.
Development of gypsy moth was more advanced in Thermes, probably due to the lower altitude. In all three localities, however, the structure of larval populations suitable for study included mid- and late-instar larvae (fourth