Polish J. of Environ. Stud. Vol. 20, No. 4 (2011), 1029-1035 Original Research Aesculus hippocastanum L. State Changes in Lithuania Vilija Snieskiene1, Antanina Stankeviciene1, Kęstutis Zeimavicius1, Ligita Balezentiene2* 1Kaunas Botanical Garden of Vytautas Magnus University, Ž. E. Žilibero 6, LT-46324 Kaunas, Lithuania 2Lithuanian University of Agriculture, Akademija, LT-53341 Kaunas distr., Lithuania Received: 17 May 2010 Accepted: 6 December 2010 Abstract Common horse-chestnut (Aesculus hippocastanum) is an introduced plant and has been successfully used for planting for a long time in Lithuania. The state of the A. hippocastanum growing in larger cities was assessed in 1992-2009. Moreover, the assessment was carried out throughout the entire country during 2006- 09. The results of the research described the changing situation of A. hippocastanum during the investigative period: the state was sufficiently good for separate periods, but it began to deteriorate in 1995-97, when a A. hippocastanum was infected with fungi diseases (agents – Guignardia aesculi, Erysiphe flexuosa, and Schizophyllum commune). Unfavourable environmental conditions had also made an influence, whereas horse-chestnut leafminer (Cameraria ohridella) was the most harmful pest over all territory of Lithuania since 2005-06. This invasive pest is common in most European countries. Noteworthy of fallen leaves elimination is the most effective mean restraining abundance of C. ohridella and the spread of fungi diseases. Keywords: Aesculus hippocastanum, diseases, pest, environment Introduction tanoides L. it reaches about 20% of all tree species used for city greening [2]. Thus A. hippocastanum is used quite Aesculus hippocastanum L. is referable to the rarely. Sapindaceae family and Hippocastanoideae subfamily. A. hippocastanum has been in a sufficiently good state This species originated from the southern Balkan peninsu- for a long time because of tolerable climatic conditions and la, in northern Greece, and in southern Bulgaria. A. hip- the absence of disease agents and harmful pests. However, pocastanum was brought from Constantinople to Western the situation has changed during recent years and the state Europe in the late 16th-early 17th centuries [1]. There are no of A. hippocastanum is deteriorating. The phytopathologi- exact records about the beginning of the introduction of A. cal state of A. hippocastanum worsened a few years earlier hippocastanum in Lithuania. Initially they were grown in in countries situated to the west and south of Lithuania. The parks of manor houses, and later this species spread causes of the impairment are both biotic (new disease because of favourable climatic conditions. Currently A. hip- agents and pests appeared over a short time) and abiotic pocastanum is a common ornamental plant in green areas (climate change). However, despite the economic impor- of Lithuanian cities. These ornamental trees are grown in tance of pests and pathogens that represent a key compo- parks, squares, on roadsides, and near country-houses. A. nent of the chestnut environment, species variation for dis- hippocastanum is not the main ornamental species in city ease resistance remains poorly understood. greeneries, as together with Acer negundo L. and A. pla- The aim of our study was to assess the factors deter- mining changes of state to the common A. hippocastanum *e-mail: [email protected] growing in Lithuania during 1992-2009. 1030 Snieskiene V., et al. Table 1. Scale of tree damage assessment. Damage degree Characteristics Point Leaf or trunk defoliation up to 10%, crown characteristic of the species, trees with- Relatively healthy 1 out signs of weakening Trees with slightly open crown reduced increment leaves, trunks or root defoliation Weakened 2 up to 11-25% Open crown highly reduced increment or its absence 26-50% of leaves, branches or Weak 3 trunks are damaged or dead Dying Crown is extremely open 51-80% of leaves, branches or trunk are damaged 4 81-100% of leaves, branches or trunk is damaged. Recently dead trees. Leaves and Dead leaves, fresh deadwood 5 branches could be with fungi mycothallus Materials and Methods After tree state assessment, the average damage grade was estimated, employing a modified procedure applied in The state of A. hippocastanum was investigated and agriculture and forestry [4] according to the formula: assessed every July during 1992-2009 in the larger cities 5 of Lithuania (Vilnius, Kaunas, Panevėžys, Šiauliai, nbii Klaipėda, Marijampolė, etc.). Due to the wide dispersal of ¦ V i 1 C. ohridella, the state of A. hippocastanum was begun to N be assessed over the entire territory of Lithuania in 55 cities and settlements in total. For more precise investiga- ...where: tion A. hippocastanum from three streets, two squares, V – average grade of damage and one park of Kaunas – the Middle Lithuania city – ni – number of plants damaged to the same grade and the were chosen. The state of approximately 1,000 trees was sum of products of the i-th grade assessed. These A. hippocastanum were observed from bi – the numeric value of the i-th grade leaf emergence in spring until their fall, and the state of N – number of checked plants tree trunk was assessed during the period when trees were Pathogens were identified according to the symptoms leafless. of diseases and fungi morphological features defined by The degree of tree damage was estimated according to descriptors [5-8]. The pests were described according to G. the method proposed by A. Ziogas et al. [3] and adapted to Deschka and N. Dimic [9]. our work. The categories of tree state were evaluated with- Statistical calculations were made using MicroSoft Exel in a 5-grade scale (Table 1). 2003. Fig. 1. Cameraria ohridella on Aesculus hippocastanum (a – damaged leaves of Aesculus hippocastanum, b – buterfly, and c – larvae of Cameraria ohridella. Aesculus hippocastanum L. State Changes... 1031 Fig. 2. Spread of Cameraria ohridella on Aesculus hippocastanum in Lithuania in 2009 (1-5 damage point). Results maturely. Stromata forms at the end of the summer and over winter inside them. In spring fruit-bodies with spores In Lithuania A. hippocastanum state was quite good and infecting A. hippocastanum emerge in stromata [10]. The stable until 1997. Later it began to change, with causes occurrence of spotting is subdued according to recent varying from year to year. In Lithuania, like in all Europe, spread of C. ohridella. new pathogenic fungi and pests appeared every few years, A new A. hippocastanum disease – powdery mildew damaging these trees (Figs. 1 and 2). (causative agent Erysiphe flexuosa (Peck) U. Braun & S. A. hippocastanum leaves injured by leaf blotch disease, Takam) was detected in Kaunas, Lithuania; in 2004. It was whose agent is Guignardia aesculi, (Peck) Stew. (anamor- also registered in Vilnius and Šiauliai in the same year [11]. pha Phyllosticta sphaeropsoidea Ellis & Everk. (syn. Cleistothecia (120-160 mm in diameter) of this fungus con- Phyllostictina sphaeropsoidea (Ellis & Everk.) Petr., sists of 3-5 ascos, each containing 6-8 unicelled ascospores Asteromella aesculicola (Sacc.) Petr.) were first noticed in [12]. This fungus originated from North America [7], where 1998 (Fig. 4). The spread of this disease is caused by cli- it is called Uncinula flexuosa, but after genetic research this matic conditions. In springtime, when the leaves of the A. hippocastanum are unfolding, the ascospores that manage 4.5 to place themselves on the leaves, germinate if leaves are 4.0 dewy for a few hours at least. And later, when fungi spread 3.5 repeatedly in conidia, the most favourable condition is wet 3.0 po and warm weather [5]. Therefore, it appeared firmly in 2.5 warm and wet summers of 1998, 2001, and 2003: average 2.0 temperature of summer months was 19.1-20.9ºC and pre- damage, Mean 1.5 cipitation was 118-144 mm. The disease symptoms include Mean damage, p 1.0 big brown irregularly-shaped spots surrounded by a yellow or brownish edge appear on leaves around the middle of the 0.5 summer; later they quickly expand and the edge of the leaf 0.0 starts curling up inward near the spots. Black fruit-bodies 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 are clearly seen in the middle of the spots. The conidia Fig. 3. Dynamics of the horse chestnut damage state in infect leaves repeatedly all summer. Injured leaves fall pre- Lithuania during 1992-2009 (mean±SE, p<0.05). 1032 Snieskiene V., et al. Guignardia aesculi Erysiphe flexuosa Necrosis Cameraria ohridella 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Fig. 4. Dynamics of horse chestnut pests, diseases agents, and necrosis damage in Lithuania during 1992-2009 (p<0.05). fungus was classified to belonging to Erysiphe genus [8]. In the seaside town Klaipėda. During 2003-04 neither C. Europe it primarily appeared in Germany around 1999 [13] ohridella nor mines were found there. However, the pres- and quickly spread to other countries: Switzerland [14], ence of mines was observed in 14 cities and towns in 2005; England [14], Slovakia [13], Slovenia [16], and Hungary this number growing to 27 in 2006 and 40 in 2007 [27]. [17]. Even though J. Buszko [26] reported C. ohridella as an inva- It was ascertained that mildew makes heavier damage sive species in Europe, it had spread throughout Lithuania in for more luxuriant A. hippocastanum growing under more 2006 as accidental species without formation of the repro- favourable conditions and also pruned trees that grow large ducing population. In 2006-07 C. ohridella were found in sprouts. A. hippocastanum, growing nearby under the same separate districts of the Latvian-Lithuanian border. conditions is not equally resistant to Erysiphe flexuosa.