In: D. Marčić, M. Glavendekić, P. Nicot (Eds.) Proceedings of the 7th Congress on Plant Protection. Plant Protection Society of Serbia, IOBC-EPRS, IOBC-WPRS, Belgrade, 2015, pp. 247 - 253

COLOUR AND SEX RATIOS IN DIFFERENT BOX TREE () POPULATIONS

Katalin Tuba, Géza Kelemen and Miklós Molnár University of West-Hungary Institute of Silviculture and Forest Protection H-9401 Sopron Pf. 132 [email protected]

Abstract

The box tree moth, Cydalima perspectalis (Walker 1859), is native to East Asia and has recently been introduced in Europe. It was first recorded in South Germany in 2007. This alien moth has been causing severe damage to topiary box tree, hedges and plants in parks, gardens, cemeteries and nurseries as well as to native populations of the box-tree (Buxus spp.) in Europe. The larvae feed on leaves but they can also attack the bark. The affected bushes die after repeated infestations. The box tree moth is a polymorph species. Our aim was to investigate the sex ratio and this polymorphism regarding the appearance of the colours in the case of the sexes. To reach these goals to use of both field and laboratory techniques were required. The number and distribution of morphs were studied in different ways. 1) Light trap data were analysed in 2013 and 2014. 2) The data received from EDDMapS were also gathered and grouped to estimate the colour and sex ratios. 3) More than 100 larvae or pupae were collected from different sites in 2013-2014. These specimens were reared under laboratory conditions. The adults were examined and classified. 4) Last but not least we also gained genetic data from crossings. Three colour morphs were divided in the Hungarian C. perspectalis populations. The white morphs with brown band on the exterior margin only and white ones with brown band both on the exterior and interior margins were observed to start almost flying together. The dark ones fly the latest and the shortest time. The first generation flies for a short time while the third one flies for the longest time. The number of males is usually higher in the population than the number of females. Our results show that the ratio of the three morphotypes varied in different habitats. It seems that the white morph appears first during the course of spread. The crossings resulted in a special ratio among the morphs. Keywords: alien species, morphotypes, distribution

Introduction its spread is the isotherm -16 °C in winter. So it might spread across most of Europe, except for North Fenno- The box tree moth is a relatively new alien species Scandinavia, northern Scotland and high mountain in Europe. It is native to East Asia (Inoue et al., 1982). regions, where the accumulated temperatures are not Its native range here is determined by the occurrence enough to allow the completion of an entire generation of its hosts and the climatic conditions. The limit of a year (Nacambo et al., 2013).

247 Cydalima perspectalis was first detected in south- 1968) and Phigalia pilosaria (Lees, 1974), western Germany in Europe in 2007, but it had oxyacanthae (Steward, 1977), and albovenosa presumably arrived in Germany a bit earlier because (Vakkari, 1980). The increase in the proportion of the infection observed was very high and extended dark Biston betularius morphotype appears to be a (Billen, 2007; Krüger, 2008; Leuthardt et al., 2010). phenomenon for which no explanation has yet been Soon it was recorded in Switzerland (Leuthardt et al., presented in the scientific literature. Bishop and Cook 2010). The box tree moth was found in the Netherlands (1980) say:”The reason is not obvious”. The melanic (Muus et al., 2009) in 2007; in France (Feldtrauer et phenotype is inherited as autosomal dominants (Grant, al., 2009), in Britain (Mitchell, 2009), in Liechtenstein 2004). Two melanic alleles are present regarding (Slamka, 2010) in 2008; in Austria (Rodeland, 2009) Phigalia pedaria moth but also occur at combined in 2009; in Belgium (Casteels et al. 2011, De Prins & frequencies of 2-18% in rural areas across the British Steeman, 2011), in Italy (Biondi, 2010), in Slovenia (Jež, Isles (Lees 1971). Steward (1977) says that selective 2012), in Hungary (Sáfián & Horváth, 2011), in the predation could be a major factor in the variation of Czech Republic (Šumpich, 2011), in Romania (Székely melanic frequencies of fagella and Allophyes et al., 2011), in Turkey (Hizal et al., 2012) in 2011; in oxyacanthae. The uniform black and the patterned Slovakia (Pastorális et al., 2013) and in Croatia (Koren intermediate form of are controlled & Črne, 2012), in Sochi in 2012; in Denmark in 2013 by separate loci. The dark one is completely dominant (Rennwald, 2015). to pale and epistatic to intermediate, and the patterned Main hosts of the box tree moth are different one is partially dominant to pale. The intensity of the boxwood species in Europe (CABI, 2013). C. whitish to yellowish background colouration is affected perspectalis larvae have been observed as causing feeding by the developing strategy. Non-diapausing are damage by chewing the leaves and tree-bark of these paler than diapausing (Vakkari, 1980). plants. Complete defoliation causes the mortality of the damaged boxwood (Albert & Lehneis 2012; Kenis et al. 2013; Leuthardt & Baur 2013; Nacambo et al. Material and Methods 2013).There are two Buxus species, which are native to Europe: B. sempervirens and B. balearica (Di Domenico The number and distribution of morphs were observed et al., 2012). However, in Asia, other reported hosts in different ways. include Ilex purpurea, Euonymus japonicas, Euonymus alatus, Pachysandra terminalis and Murraya paniculata 1) Light trap data were analysed from the beginning of (Korycinska & Eyre, 2011; Wang, 2008). The natural May until the end of October 2013 and 2014. The light populations of Buxus are seriously threatened by C. trap was situated in Sopron where the first C. perspectalis perspectalis (Kenis et al. 2013). Cultivated boxwood was caught in Hungary in 2011. The different sexes and plants in parks, cemeteries and gardens are also colours were separated each day. damaged by this pest under urban conditions. 2) Photos of the moth received from EDDMapS were There are several species that have morphotypes. also gathered and grouped to estimate the ratios of the The morphological differences can appear in different colours and sexes. EDDMapS is an Early Detection and developmental stages. The causes of these phenomena Distribution Mapping System, which has been operated originate under different conditions. Two sympatric by Bugwood Network since 2008. Our institute has colour morphs of Zeiraphera diniana were described adopted this system and adjusted to the Hungarian that are distinguishable only during the final larval conditions. Spreading data of C. perspectalis have been stage; the dark one is found mainly on Larix decidua collected with this system in Hungary since March 2012. and the orange-yellow morph occurs on Pinus cembra 3) One hundred larvae were collected in Gyöngyösfalu (Bovey & Maksymov, 1959). Larvae of Zeiraphera and Sopron in May 2013, and one hundred pupae diniana were raised continuously or at least during their were gathered in Kőszeg and Pápa, Hungary in June latter larval stage at 10 °C were darker than larvae reared 2014. These specimens were reared under laboratory at 18 °C (Baltensweiler, 1977). Nutritional stress causes conditions (20 °C, 16L:8D photoperiod). The larvae an increase in frequency of intermediate morphotypes were fed with leaves of boxwood. The adults were in subsequent generations (Day & Baltensweiler, 1972). examined and classified based on colour and sex. Two or more morphs may be recognised e.g. in the 4) Last but not least we also gained data from crossings. cases of Odontopera bidentata (Kettlewe, 1959; 1973), This survey was carried out in a period of two years. Four Biston betularius (Clarke & Sheppard 1964; Lees, pairs of the moth were placed in a 40x25x25 cm box, and

248 they were fed with a mixed solution of honey and water. on the exterior and interior margins (of the forewing) The larvae hatched were placed into a 0.5 l plastic box. The (hereafter white with brown margin) and 3) the melanic rearing method was similar to that in the case of larvae (greyish-brown) form. and pupae (3). Regarding this examination the white with brown band on the exterior margin only and the 1) Light trap data white with brown band both on the exterior and interior The catches of the light trap show similarity in margins morphs were handled together, because it was not colours and between years. The number of females was possible to do proper crossings among the three morphs a slightly higher than the number of males. Considering neither next to high number of population in same time. the females the melanic form occurred in the highest ratio, while the white with brown margin form was the most frequent among the males (Tab. 1). Results The flight periods of the three colour morphs were variable but partly overlapping. The white and white In Hungary, three colour morphs were observed. 1) with brown margin morphotypes have a bit longer flight The white with brown band on the exterior margin only periods. The melanic form starts to fly later than the (hereafter white) 2) the white with brown band both other two forms (Fig. 1).

Table 1. Colour and sex ratios of C. perspectalis morphotypes based on catches of the light trap

Male Female White White with brown margin Greyish-brown White White with brown margin Greyish-brown 2013 10.1 19.4 17.0 13.2 19.3 21.0 2014 8.5 20.3 13.6 11.9 22.0 23.7

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249 2) EDDMapS data the sample of larvae were collected in May 2013 the EDDMapS data show that the white morph was the melanic morph was the most frequent. In Kőszeg, dominant in comparison of the recognised specimens (Fig. 2). where the moths were found in June 2013 and the The results regarding the data of the observations suggested sample was gathered in July 2014 the white with brown that the first moths emerge between the white morph. margin reached the highest number. In Gyöngyösfalu, where the larvae were found in Augustus 2013 and 3) Results of rearing in Pápa, where the larvae were found in Augustus There were not big differences between the two sexes 2014 and the samples were collected directly after the regarding the ratios of the colours. In Sopron, where finding the most frequent morph was the white type C. perspectalis was recognised in September 2011 and (Fig. 3, Fig. 4).

Figure 2. Occurrence of the three morphs of C. perspectalis based on public notifications

60 54

50

40

28 % 30 27 20 18 20 16 11 9 10 7 8 2 0 0 White White Greyish White White Greyish White White Greyish White White Greyish with brown with brown with brown with brown brown brown brown brown margin margin margin margin Male Female Male Female Gyöngyösfalu Sopron

Figure 3. Colours and sex ratios of the reared C. perspectalis larvae

250 4) Results of crossing Our result shows that the ratio of the three morphotypes The results of the crossing indicated a special ratio was different at different locations. It seems that the most between the white and white with brown margin together frequent colour form may correlate with the length of the and greyish-brown colour morphs in both years. We period after the ecesis or with the number of generations can also find a similarly special ratio by analysing the (1st, 2nd or 3rd). Directly after ecesis the white morph relationship between the sexes (Fig. 5). dominates in the habitats, while one year later (3-5 generations) the white with brown form reach the highest number, while later (6-9 generations) the melanic form is Discussion present in the highest number. The other explanation is that the melanic morphs reach a higher number in the The white and the white with brown margin morphs first generation, the white with brown margin morphs of C. perspectalis were found to start to fly earlier than reach a higher number in the second generation while in the dark ones. The first generation flies for a short time the third generation the white form can be found in the while the third one flies for the longest time. The males of highest number. This phenomenon may correlate with the box tree moth hatched earlier than the females. The the temperature or the length of the day. However, further white morph appears first during the course of spread. examinations are needed to answer this question.

45 39 40 35 30 30 27 25 25 % 20 16 15 12 13 10 8 10 7 7 6 5 0 White White Greyishy White White Greyishy White White Greyishy White White Greyishy with brown with brown with brown with brown brown brown brown brown margin margin margin margin Male Female Male Female KĘszeg Pápa

Figure 4. Colours and sex ratios of the reared C. perspectalis pupae

90 80 72,9 70,4 70 60

% 50 38,9 38 40 34 32,4 27,1 29,6 30 1616,9 9 20 12,5 14,6 12,7 10 0 White Greyish White Greyish White Greyish White Greyish White Greyish White Greyish brown brown brown brown brown brown Male Female Both sexes Male Female Both sexes together together 2013 2013 2014 2014

Figure 5. Results of the C. perspectalis crossing experiment

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