Silva Balcanica, 16(1)/2015

First record of the invasive Elm Aproceros leucopoda Takeuchi (: ) in Bulgaria

Danail Doychev University of Forestry – Sofia

Absract

East Asian sawfly Aproceros leucopoda Takeuchi (Hymenoptera: Argidae) was found for first time in Bulgaria. Adults, larvae, cocoons and typical damaged leaves were observed and collected on Ulmus minor Mill. from five sites in Western Balkan Range and Sofia. The larval damages on the host trees were too insignificant – between 1 and 2%.

Key words: Aproceros leucopoda, Ulmus, invasive species, new record, Bul- garia

Defoliating belong to the most important pests on trees in forestry and urban green spaces. Their mass outbreaks can cause considerable damages leading to high economical loses or reducing the tree ornamental effect. Along with common lepidopteran and hymenopteran phylophages, such as Lymantria dispar (L.), Eu- proctis chrysorrhoea (L.), Thaumetopoea pityocampa (Den. & Schiff.), Neodiprion sertifer (Geoff.), an extremely invasive pest of unknown origin, the horse chestnut leaf miner Cameraria ochridella Deschka & Dimic, has spread out in the last 20 years over whole Europe, including Bulgaria (Trenchev et al., 2000; Péré et al., 2010). Besides, another dangerous invasive insect species were also found and reported on different forest tree and shrub species in Bulgaria: Corythucha ciliata (Say) on Platanus spp. (Josifov, 1990), senticetella (Staudinger) on Juni- perus excelsa M. B. (Mirchev et al., 1995), Fenusella hortulana (Klug) on Populus x euramericana Dode (Guinier) (Georgiev, 2006), Myzocallis walshii (Monell) on Quercus rubra L. (Tasheva-Terzieva et al., 2008) and Corythucha arcuata (Say) on Q. robur L. and Q. cerris L. (Dobreva et al., 2013). Since 2003, another invasive species – the East Asian sawflyAproceros leuco- poda Takeuchi, 1939 (Hymenoptera: Argidae) has colonized the elm trees in South- Eastern Europe and several defoliations were even observed until now (Blank et al., 2010). This paper reports A. leucopoda for first time for Bulgaria. The investigations were conducted in June 2015 in five localities (Table 1). The first one is situated in Western Balkan Range near Cherepish Monastery, and the rest are placed in Sofia. Various stages of A. leucopoda have been found on the host

108 tree Ulmus minor Mill. – larvae, pupae, adults and damaged leaves with typical zig- zag larval feeding traces. Collected larvae and cocoons were placed in plastic boxes with elm leaves for rearing in the laboratory of University of Forestry, Sofia. The adults and larvae were identified by the keys of Blank et al. (2010). In localities N1 and N5, where more visible damages occurred, 752 and 2201 randomly selected leaves, respectively, were examined from each of all seven trees and the percentage of damaged leaves by larvae was calculated.

Table 1 Characteristics of localities and studied biological material of A. leucopoda on U. minor

Altitude, Geographic N Locality Biological material m coordinates Western Balkan Range, 43° 05’ 45.98” N 14 leaves damaged, 8 larvae and 1 ♀ 1 500 m NW of 280 23° 36’ 37.01” E 6 June 2015 Cherepish Monastery Sofia, 42° 41’ 16.41” N 2 ♀♀ 2 550 Borisova gradina 23° 20’ 21.27” E 7 June 2015 Sofia, 42° 40’ 44.41” N 2 leaves damaged 3 Gorna banya 680 23° 14’ 18.50” E 09 June 2015 Residential Area Sofia, G. M. Dimitrov 42° 39’ 47.48” N 2 leaves damaged 4 580 Metro Station 23° 21’ 23.93” E 11 June 2015 25 leaves damaged, 2 empty cocoons 17 June 2015 9 ♀♀ reared by larvae 17 June 2015 (cocoons: 19-23 June, Sofia, Mladost 2 Residen- 42° 38’ 58.59” N adults emerged: 26-29 June) 5 590 tial Area 23° 22’ 00.53” E 2 ♀♀ reared by larvae 20 June 2015 (cocoons: 24 June, adults emerged – 28 June) 1 ♀ reared by cocoon collected on 20 June 2015 (adults emerged 27 June)

First, A. leucopoda was found by chance in Western Balkan Range at the be- ginning of June 2015 and in the next days some places in Sofia were observed for it. A total of 15 female adults of A. leucopoda were collected, most of them reared by larvae found on the leaves of U. minor. In addition to presented localities, 40 trees of Ulmus laevis Pall. have been observed in Yuzhen Park in Sofia on 12 June 2015 but no damages by Elm sawfly were found. Aproceros leucopoda occurs naturally in East Asia – Japan (Takeuchi, 1939; Naito, 2004), China (Wu, Xin, 2006) and Russian Far East (Zhelochovtsev, Zinovjev, 1995). In Europe it was collected for first time in 2003 in and Poland (Blank et al., 2010). Actually, in Moldova A. leucopoda has been reported earlier than other European countries (Timuş et al., 2008) but misidentified as Arge

109 sp. Later, it has been also found in , Romania, , (Blank et al., 2010), (Zandigiacomo et al., 2011), (Kraus et al., 2011, Sobczyk, Nuss, 2014; Blank et al., 2014), Slovenia (de Groot et al., 2012; Seljak, 2012), Croa- tia (Matošević, 2012), European Russia (Artokhin et al., 2012), (Boevé, 2013), Serbia (Glavendekić et al., 2013), the Netherlands (Mol, Vonk, 2014) and Czech Republic (Jurášková et al., 2014). The presented localities in Bulgaria are the southernmost points of hitherto known A. leucopoda distribution in Europe. The level of damages on leaves in Bulgaria was very low - 1.73% for local- ity N1 and 1.14% for N5 but severe defoliations and outbreaks (up to 100%) have been observed in Romania, Hungary and Germany (Blank et al., 2010; 2014). The preferred host trees in Europe are U. minor and U. glabra Huds. but larvae feed also on U. laevis and cultivated U. pumila L. (Blank et al., 2010). The presence of A. leucopoda can be easily recognized. The young larvae feeding traces have a typical zigzag pattern (Fig. 1A), later leaves are consumed between lateral veins predominantly (Fig. 1B) and finally almost the mid vein only remained (Fig. 1C). Larvae have greenish body with T-shaped marks on the second and third prolegs (Fig. 1D). A transversal lateral dark stripe crosses the head capsule reaching stemmata. The last instar larvae make a summer net-like cocoon underside of leaves (Fig. 1E, F). Overwintering pupae have more compact, solid-walled co- coon in the litter or the soil. The adult wasp is dark brown to black with light yellow or white legs and palpi (Fig. 1G). A. leucopoda is parthenogenetic, multivoltine species with four generations per year. The adults can be found from April to September (ibid.). Most probably the present observed stages (larvae, damages and cocoons with pupae) belong to the second generation. Undoubtedly A. leucopoda is more wide- spread in Bulgaria but the lack of considerable damages until now may be due to unfavourable abiotic conditions (warmer and drier climate) or just early stages of its invasion.

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110 Fig. 1. A – Zigzag feeding track of young Aproceros leucopoda larva; B – feeding tracks of older larvae; C – final stage of the larval damages on elm leaf; D – mature larva of A. leucopoda; E – net-like cocoon containing an eonymph; F – cocoon with imago ready to emerge; G – female adult of A. leucopoda

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