UDK 630* 453 Pregledni članci – Reviews Šumarski list, 11–12 (2016): 577–588 P OTENTIALLY IMPORTANT INSECT PESTS OF CELTIS AUSTRALIS IN SLOvENIA, CROATIA ANd HUNGARY POTENCIJALNO ZNAČAJNI ŠTETNI KUKCI NA Celtis australis U SLOVENIJI, HRVATSKOJ I MAđARSKOJ Maja JURC1, György CSÓKA2, Boris HRAŠOVEC3 Summary We have collected published data and carried out pilot studies on European nettle tree (Celtis australis) entomo- fauna in Croatia, Slovenia and Hungary. Seven taxa of Lepidoptera (Libythea celtis, Nymphalis polychloros, Archips xylosteana, Erannis defoliaria, Caloptilia fidella, Phyllonoricter millierella and Hyphantria cunea), one cerambycid (Neoclytus acuminatus) and one hemipteran (Metcalfa pruinosa) were found. Two species of Lepidoptera (L. celtis and P. millierella) are monophagous on the leaves of C. australis. The other recorded species are also known on other woody hosts. For N. polychloros, A. xylosteana, E. defoliaria, C. fidella and N. acuminatus European nettle tree is a new host plant. The monophagous species of butterflies onC . australis have appeared more frequently in the last decade. The results are intended to predict whether this tree species is suitable for introduction on a wider scale in pine plantations of Pinus nigra affected by climatic extremes, pests and diseases, such as sphaeropsis blight (Diplodia pinea). Taking into the account the potential rise and growing impact of European nettle defoliators, which, according to some projections will prosper in the future due to global warming, some reservations arise and reduction of C. australis viability are to be expected. KEY WORdS: Celtis australis, Southern/Central Europe, insects, defoliators, Lepidoptera, Coleoptera, Hemiptera INTROdUCTION (Brus 2005). C. australis is a popular ornamental tree in the UVOD cities of the Sub-Mediterranean area. European nettle tree (Celtis australis L., Urticales, Ulma- C. australis is resistant to drought, wind and air pollution ceae) is a deciduous tree native to the Mediterranean region in cities and is able to withstand temperatures as low as –15 (Southern Europe, North Africa), and it also appears in Asia °C (Potočić et al. 1983). It prefers light, sandy soil and warm, Minor, the Crimea and in the area from the Caucasus to dry limestone terrain. C. australis is a light-loving species. Iran (Potočić et al. 1983). The northern boundary of its area Hence, it is suitable for the afforestation of karstic and dry is Switzerland, where it appears from 800 to 900 meters terrain (Jovanović 1971, Matić et al. 2011). above sea level (Jovanović 1971). On warm South Tyrolean In Slovenia its habitats are sunny, rocky slopes in the Pre- slopes it can even be found up to 1,150 m above sea level Alpine (probably introduced) and Sub-Mediterranean 1 Prof. dr. sc. Maja Jurc, University of Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, SI-Slovenia, Ljubljana, [email protected] 2 Dr. sc. György Csóka, NARIC Forest Research Institute, Department of Forest Protection, H-Hungary, 3232 Mátrafüred, Hegyalja str. 18, [email protected] 3 Prof. dr. sc. Boris Hrašovec, University of Zagreb, Faculty of Forestry, Svetošimunska 25, CRO-10000 Zagreb, [email protected] 578 Šumarski list, 11–12, CXXXX (2016), 577–588 phytogeographic regions (Martinčič et al. 2010). It is com- in the processes of degraded site re-cultivation in the Cro- mon in the Mediterranean area (Kraški rob, Dragonja atian Mediterranean area (Matić et al. 2011). Climatic extre- Valley), but more rare in the Karst area, where it appears in mes, especially drought, can be considered the basic adverse a valley between Brestovica and Gorjanski near Solkan and factor causing stress and physiological weakening of pine in the Vipavska Valley. In warmer Mediterranean and Sub- trees and simultaneously improving the conditions for Mediterranean forests, C. australis grows as an individual attacks of various types of pests. tree or in groups with Quercus pubescens Willd., Fraxinus The conversion of old black pine plantations into ecologi- ornus L., Pistacia terebinthus L. and other thermophilic tree cally more stable broadleaf forests is an important goal in species. It grows on steep, rocky, dry karst areas, protecting many Mediterranean countries. Some native deciduous spe- the soil against erosion (Brus 2005). cies as C. australis, Quercus petraea (Matt.) Liebl., Prunus In Croatia C. australis is indigenous in Istria and throug- avium L., Juglans regia L. and other were used experimen- hout the whole Mediterranean area (Potočić et al. 1983; tally to achieve this gool. Based on their high survival rates Matić et al. 2011). after the first growing season, all tested species showed pro- In Hungary there are some monumental introduced C. au- mising potential for future conversion of old pine stands in stralis trees in the central part of the country (in Dég, at the the Slovenian and Croatia (Topić 1997, Gajšek et al. 2015). Danube river shores in Adony, in Mezőhegyes, Kajdacs, Al- This paper aims to summarize the literature data and the sóhídvégpuszta (county of Tolna)), (Monumental trees at results of our own pilot studies on herbivorous entomofa- Alsóhídvégpuszta… http://www.monumentaltrees.com/ una on C. australis in Slovenia and Croatia, where this tree en/hun/dunantul/tolna/3920_alsohidvegpuszta/). species is native in Mediterranean area, and in Hungary, C. australis is a long-lived, 15–20 m tall tree, reaching a di- where the C. australis has been introduced and planted. The ameter of 1–2 m and an age of 1,000 years, with quality results are intended to give some deciding whether this tree wood (the genus name derives from the Greek word kello species could be introduced on a wider scale in plantations – driven, because of its hard wood used for whips). The of P. nigra in Slovenian and Croation Mediterranean. wood is stiff, with gray colored hardwood and yellow sa- pwood and is suitable for carving, making musical instru- ments, sports equipment, paddles, etc. The young shoots MATERIALS ANd METHOdS are slender and wiry, suitable for whips and rods. The root MATERIJAL I METODE system is strong and deep. The leaves alternate; they are Observations of health status on C. australis 5–12 cm long, simple, with serrate edges; the leaf surface is in the studied area – Opažanja zdravstvenog stanja asymmetrical and with three stronger vessels. The flowers C. australis u području istraživanja are polygamous or hermaphroditic, small, apetalic, with 4–5 stamens, appearing on young shoots. The fruit is round, up On September 8, 2011 on the Dekani location near Koper to 1 cm thick, with a sweet and edible wrapper (Jovanović (Slovenia), we collected 15 branches of C. australis with vi- 1971; Brus 2005). sibly damaged leaves (mines), and on the basis of the symp- Interestingly, according to literature data, C. australis has toms of the damage, the pest species was identified. In 2013 only a few diseases. Some earlier authors, such as Kišpatić we screened a wider area of the Sub-Mediterranean zone in (1983) (Potočić et al. 1983), note that C. australis is rarely Slovenia and assessed various symptoms of biotic damage infected by fungi, such as Laetiporus sulphureus (Bull.) on C. australis. On May 5, 2014, in the Brseč location near Murrill (1920) and Ganoderma applanatum (Pers.) Pat., Opatija (Croatia) (Figure 1), a similar screening procedure which cause rot in old trees. In the monograph Insects and was conducted in an urban environment during a strong diseases damaging trees and shrubs of Europe (Zúbrik et outbreak and total defoliation of European nettle tree al. 2013) only one species (Phyllonoricter millierella (Stau- crowns. We collected 18 branches of C. australis with hea- dinger, 1877)) from C. australis is listed. Aside from these vily consumed leaves with different species of lepidopteran few observations, very little is known about the herbivore larvae. The diameter of twigs averaged 0.8 cm, and total insect assemblages of C. australis, and, to our best length was 3.9 m. They were grown in entomological rea- knowledge, no reports on the health condition of C. austra- ring containers at room temperature until October 1, 2014. lis in recent years exist from other countries within its range. All insects present on the twigs (number / diameter / length Afforestation of the Karst region in south-western Slovenia of twigs, dead larvae, left pupal exuviae, dead pupae, adult began in the 19th century, when the first successful black moths) were analyzed and species identified. Some lepidop- pine (Pinus nigra Arnold) plantations were established and teran species were identified in larval stages according to over time, black pine plantations improved site conditions their specific caterpillar features (Csóka 2003) and on the considerably (Škulj 1988). Black pine was also irreplaceable basis of photos taken at the Brseč location. JURC, M. i dr.: POTENTIALLY IMPORTANT INSECT PESTS OF Celtis australis IN SLOVENIA, CROATIA AND HUNGARY 579 cerambyx.uochb.cz/neoclyt.htm). In August 2006 Hosko- vec collected a dead piece of C. australis wood with ceram- bycid larvae and after rearing identified them asNeoclytus acuminatus (Fabricius, 1775). In 2008 a heavy attack and total die-back of C. australis trees in street plantings in Novi Vinodolski (Croatia) were caused by the same cerambycid (Hrašovec 2009). The outcome of the laboratory experiment of rearing field sampled larvae from European nettle trees taken in Brseč on May 5, 2014, was 40 dead caterpillars, 48 dead undeveloped pupae, 90