Cristulariella depraedans as causal agent of leaf spots of a maple and other trees and shrubs TADEUSZ KOWALSKI and CZESŁAW BARTNIK Department of Forest Pathology, University of Agriculture in Kraków Al. 29. Listopada 46, PL-31-425 Kraków, rltkowal@cyf-kr.edu.pl Kowalski T., Bartnik Cz.: Cristulariella depraedans as causal agent of leaf spots of maple and other trees and shrubs. Acta Mycol. 43 (1): 5–12, 2008. Results of the first studies in Poland on Cristulariella depraedans, the causal agent of necroses on tree and shrub leaves, are presented. The fungus was recorded on Acer platanoides, A. pseudoplatanus and eight other species of trees and shrubs, including Corylus avellana, Fagus sylvatica, Lonicera xylosteum and Padus avium that were not previously known as hosts of the fungus. The disease symptoms, which depend on the host plant species, the size and number of necrotic lesions on leaves, and the morphological features of the fungal propagules were characterized. Key words: Cristulariella depraedans, Acer spp., leaf spots, host range INTRODUCTION Many and various symptoms with abiotic and biotic causes occur on leaves of maple trees, Acer platanoides L. and A. pseudoplatanus L. Only some of them are easily recognizable.These include symptoms caused by fungi, e.g. Rhytisma acerinum (Pers.) Fr. and R. punctatum (Pers.) Fr. (Butin 1996; Mańka 2005) or by gall-form- ing insects and mites, e.g. Harrisomyia vitrina (Kieffer) and Eriophyes pseudoplatani Corti (Skrzypczyńska 2004). The joint action of fungi and gall-forming insects in the development of necroses can make the diagnosis of their causal agents difficult. Kowalski (2003) recorded 18 species of fungi within the necrotic areas accompanying the galls caused by Drisina glutinosa Giard. The most significant were Colletotrichum gloeosporioides (Penz.) Sacc., Diplodina acerina (Pass.) Sutton, Discula campestris (Pass.) Arx and Phomopsis platanoidis Died. Similar associations were reported by Wulf (1990), who found 12 species of fungi on leaves of A. pseudoplatanus within the necrotic tissues of galls caused by Dasineura vitrina Kieffer. A great variety of fungi can infect maple leaves and recognition of symptoms and signs caused by individual potential causal agents is necessary. ACTA MYCOLOGICA Vol. 43 (1): 5–12 2008 6 T. Kowalski and Cz. Bartnik Studies on diseases of forest trees in the south of Poland led to the identification of Cristulariella depraedans (Cooke) Hoehn., a fungus that occurred commonly on maple leaves in a few locations. Since the species has not been recorded in Poland previously, the objective of this study was to present an analysis of symptoms and signs of infection by the pathogen on maple tree leaves. The symptoms on leaves of the other species of trees and shrubs growing in proximity to the infected maples were also analysed to indicate the pathogen’s hosts range. MATERIALS AND METHODS The study was carried out in 1996-2006, in four localities in the south of Poland (Tab. 1). The majority of observations were made in Ojców National Park, where the trees and shrubs along a route that included the Łokietek Cave, Ojców centre, Prądnik valley, the Kraków Gate and again the Łokietek Cave were surveyed and analysed. From July to October, 1-3 times a year, 30 to 60 leaves with different dis- ease symptoms were collected from 30 trees, mostly self-sown, of Acer pseudopla- tanus and A. platanoides. Samples were either from young trees or from the lower parts of the crowns of older trees. On each occasion, 3-6 diseased leaves from each of 20 other species of trees and shrubs growing in the surrounding area were also collected and assessed (Tab. 2). Their grouping according to the type of symptoms and the presence of sporulation of C. depraedans was made in the laboratory. The number and size of necrotic lesions caused by C. depraedans on 165 maple leaves collected at random from severely affected trees were evaluated. The sizes of similar lesions on leaves of the other species of trees and shrubs and the pigmentation of the necrotic tissues in the centres of the lesions and at their borders with the living leaf tissues were also determined. The propagules formed by C. depraedans were examined microscopically and a macro- and microphotographic record was made of the symptoms and signs of infection by C. depraedans. The nomenclature of host plants is given after Mirek et al. (2002). RESULTS Cristulariella depraedans was recorded in four localities in the south of Poland (Tab. 1). It was common in Ojców and Tatra National Parks and Wolski Forest (Tab. 3) but occurred only sporadically in Świerklaniec Forest District. In Ojców National Park, most infection was recorded in 1996-1998, when more than 80% of trees grow- ing along the route surveyed had local necrotic lesions caused by C. depraedans on their leaves. In a few young maple trees, up to 1 m high, all leaves in the crowns were infected (Fig. 1). In Tatra National Park, Świerklaniec Forest District and Wolski Forest, C. de- praedans occurred only on leaves of A. pseudoplatanus, and in Ojców National For- est it occurred on both species of Acer and on eight species of other trees and shrubs, viz. Carpinus betulus, Cornus sanguinea, Corylus avellana, Fagus sylvatica, Lonicera xylosteum, Padus avium, Quercus robur and Tilia cordata. There were no symptoms of infection by C. depraedans on a further 12 species of trees and shrubs growing in the area surrounding the infected maples (Tab. 2). Cristulariella depraedans 7 Some differences were observed in the symptoms caused by C. depraedans on A. pseudoplatanus and A. platanoides, and on other plant species. Up to 438 necrotic lesions per leaf, with lesion diameters up to 22 mm, occurred on A. pseudoplatanus (Tabs 2, 3). Single lesions were almost round, greyish-white in the centre and dark grey at the edge (Tab. 2; Figs 1, 2). Ta b l e 1 Locations and periods of study and plant species examined (E, examined; N, no symptoms and not examined) Area studied Period of studies Number of observations in a year Species of plants studied Acer platanoides Acer pseudoplatanus Other species of tress and shrubs Ojców National Park 1996-2002, 2006 2 - 3 E E E Tatra National Park 1999-2002, 2005 1 N E E Świerklaniec Forest District 1999-2002, 2006 1 - 2 N E E Wolski Forest 2001-2002 1 N E E List of species is given in Table 2 Ta b l e 2 Presence, size and appearance of lesions caused by Cristulariella depraedans on different trees and shrubs Species of plant Size of necrotic spots Colour of centre Colour of edge (mm) A. Plants with Cristulariella depraedans Acer platanoides L. 1-33 light grey to dark grey to light brown dark brown Acer pseudoplatanus L. 1-22 greyish-white dark grey Carpinus betulus L. 1-3 grey to dark grey light brown brownish-grey Cornus sanguinea L. 1-3 grey violet Corylus avellana L. 1-3 light brown greyish-brown Fagus sylvatica L. 1-2 grey grey or greyish-green Lonicera xylosteum L. 1-5 whitish-grey dark grey Padus avium Mill. 1-3 whitish-grey greyish-brown or greyish-green sometimes with a purplish tint Quercus robur L. 1-6 light beige light brown Tilia cordata Mill. 1-2 light grey dark grey B. Plants with no Cristulariella depraedans Aesculus hipocastanum L. Salix fragilis L. Alnus glutinosa (L.) Gaertn. Sambucus nigra L. Betula pendula Roth. Sorbus aucuparia L. Fraxinus excelsior L. Spiraea salicifolia L. Populus tremula L. Symphoricarpos albus (L.) S.F. Blake Quercus rubra L. Ulmus glabra Huds. 8 T. Kowalski and Cz. Bartnik Germinating C. depreadans propagules were often seen within the initial and smallest lesions. Disintegration of the necrotic tissues caused irregular perforations between the leaf veins in a few of the more advanced lesions. Single, adjacent lesions sometimes merged and the severely infected leaves rolled up, died and were shed prematurely, often as early as August. Up to 338 local lesions per leaf occurred on A. platanoides (Tab. 3). Small lesions were 2–5 mm in diameter and larger lesions reached up to 33 mm in diameter (Tab. 3, Fig. 3). The lesions were light grey to light brown in the centre and dark grey to dark brown at the edge. As on leaves of A. pseudoplatanus, germinating propagules of C. depraedans were often seen within the initial and smallest lesions (Fig. 4). Lesions caused by C. depraedans on leaves of A. pseudoplatanus at Ojców National Park were larger than those recorded at the same time at Tatra National Park (Tab. 3). Ta b l e 3 Numbers and size ranges of lesions caused by Cristulariella depraedans on leaves of Acer platanoides and A. pseudoplatanus at different periods of study Studied area Period of studies Number of leaves Summary number of necroses with diam (mm) (minimal and maximal number on a leaf) < 5 6-10 > 10 Acer platanoides Ojców National Park VIII.1997 10 706 63 73 (2-308) (2-16) (2-14) Ojców National Park VIII.2000 10 710 146 30 (32-113) (8-26) (1-6) Ojców National Park VIII.2001 10 340 52 46 (4-91) (0-11) (1-9) Acer pseudoplatanus Ojców National Park VIII.1997 30 4435 122 11 (12-373) (0-25) (0-6) Ojców National Park VIII.2000 30 5863 423 12 (18-399) (1-37) (0-2) Ojców National Park VIII.2001 30 4501 172 14 (42-321) (1-14) (0-3) Tatra National Park VIII.2000 15 557 0 0 (9-107) (0-0) (0-0) Tatra National Park VIII.2002 15 1721 46 2 (0-219) (0-11) (0-1) Wolski Forest X.2001 15 442 155 57 (3-104) (4 29) (0-8) Cristulariella depraedans 9 Leaves of other species of plants were infected by C. depraedans to different extents. The largest numbers of necrotic lesions per leaf were recorded on Cornus sanguinea (up to 582) and on Quercus robur (up to 286) (Figs 7, 9). Lesions diam- eters were between 1 and 6 mm (Tab. 2). The necrotic tissues showed more or less distinctive differences in pigmentation of the central and peripheral parts in all the species of plants studied (Tab. 2). The near-violet pigmentation of the lesion edges on leaves of Cornus sanguinea and greyish-green pigmentation on leaves of Padus avium and Fagus sylvatica were the most characteristic (Tab. 2, Fig. 9). Differences in pigmentation of these tissues were not species-specific. A similar range of pigmenta- tion was observed during these studies on leaves of C. sanguinea infected by Septo- ria cornicola Desm., of P. avium infected by Stigmina carpophila (Lev.) M.B. Ellis, and on a few leaves of F. sylvatica in the necrotic tissue surrounding galls caused by Mikiola fagi (Hartig) and inhabited by Apiognomonia errabunda (Rob.) Hoehn. The whitish propagules of C. depraedans, which were clearly discernible against the greyish background of the lesions, were observed in the necrotic areas on the undersides of leaves and sometimes also on the upper surface of the leaf blades (Fig. 5). Propagules were bulb-shaped, round, slightly flatten or slightly elongated 60 – 140 µm in diameter, mounted on a septate, hyaline stipe, 120 – 180 µm long and 10 – 15 µm wide (Fig. 6). The bulb, which consisted of many single, round cells, 6 – 9 µm in diameter, was readily separated from the stipe. DISSCUSION The fungus Cristulariella depraedans has been known since the end of 19th cen- tury, when it was described as Polyactis depraedans Cooke (Cooke 1885). It is not a commonly occurring species. It has been recorded previously only in the United Kingdom, Germany, Austria and the USA (Cooke 1885; Saccardo 1908; Sydow 1912; Bowen 1930; Batko 1974; Butin 1981a; Cech, Donaubauer 1990; Wulf 1994). The present studies show that it also occurs in the south of Poland, where it was first re- corded in Ojców National Park. Its occurrence in abundance was associated mainly with heavy rainfall in the growing season of 1996-1997 (Feliksik et al. 2002; Saramak 2005). The significance of wet conditions for the development of the fungus was also noticed and emphasized by Bowen (1930), Butin (1981b), Cech and Donaubauer (1990), Wulf (1994) and Lang (2000). Favorable moisture conditions can be also found on the leaves of susceptible young trees regenerated naturally and growing under the canopy of older stands. In Ojców and Tatra National Parks, favourable moisture conditions occur in the numerous depressions and valleys. For more than 100 years the host range of C. depraedans has been known to include various species of Acer, Bucida buceras L. and Aruncus dioicus (Walt.) Fern. (Redhead 1975; Lang 2000). Only recently studies in Germany in 1996-1999 showed that C. depraedans has a much broader potential host range than known previously. Lang (2000) reported its occurrence on 21 woody and herbaceous plants other than Acer species. The present studies also confirmed that the host range of C. depraedans is not limited to plants within genus of Acer. In Ojców National Park, the fungus was observed on eight other species of plants growing in the areas around the in- fected A. platanoides and A. pseudoplatanus. Four of them, Corylus avellana, Fagus 10 T. Kowalski and Cz. Bartnik sylvatica, Lonicera xylosteum and Padus avium, are new additions to the host range of C. depraedans. Lang (2000) showed that the size and pigmentation of necrotic lesions and their edges, next to the living leaf tissues, depend on the species of host plant and are re- lated to differences in their susceptibility. Lesions were different in size on leaves of A. pseudoplatanus, A. platanoides and the other plant species studied. This undoubt- edly resulted from the interval of time between infection and observation. It should be mentioned that propagules formed within lesions were transferred to other leaves and to other parts of the leaf that had the primary infection, and caused secondary infections at different times in the same growing season. Occasionally, germinating fungal propagules were observed on the initial necroses, with diameters not exceed- ing 1 mm, in the second half of the growing season. Despite the differences in le- sion sizes resulting from the period of infection, effects of host plant on the lesion dimensions were also observed. The larger lesions on leaves of A. platanoides seem to suggest that it is more susceptible than A. pseudoplatanus. The propagules of C. depraedans found in Poland did not differ morphologically from those found in other countries (Redhead 1975; Willetts 1997; Butin 1981b; Wulf 1994). Their presence is essential for the identification of C. depraedans be- cause the lesions are not specific and are very similar to those caused by other fungi or insects and mites causing galls (Kowalski 2003; Skrzypczyńska 2004). The present studies confirm that, on the plants examined, there was no co-oc- currence of a related species, Cristulariella moricola (Hino) Redhead (syn. C. py- ramidalis Waterman & Marshall), which has propagules that are of different shape (Redhead 1975; Trolinger et al. 1978). Acknowledgement. The study was supported by the Ministry of Science and Higher Education, grant no. 2 P06L 036 26. REFERENCES Batko S. 1974. Notes on new and rare fungi on forest trees in Britain. Bull. Br. Mycol. Soc. 8: 19–21. Bowen P. R. 1930. A maple leaf disease caused by Cristulariella depraedans. Conn. Agric. Exp. Stn. Bull. 316: 625–647. Butin H. 1981a. Aktuelle Baumkrankheiten im Forst. Mitt. Biol. Bundesanst. Land – Forstw. Berlin- Dahlem. 203: 177–178. Butin H. 1981b. Die Weißfleckigkeit des Bergahorns – eine „neue“ Blattkrankheit. Allg. Forstzeitschrift. 14: 327-328. Butin H. 1996. Krankheiten der Wald- und Parkbäume. Thieme Verlag. Stuttgart. Cech T. L., Donaubauer E. 1990. Cristulariella depraedans – Weissfleckenkrankheit von Ahornblättern. Forstschutz Aktuell. 12: 3. Cooke M. C. 1885. Some remarkable moulds. Jour. Quek. Micr. Club. S. II, 2: 138–143. Feliksik E., Wilczyński S., Durło G. 2002. Charakterystyka zmienno�ci opadów atmosferycznych na Kop-Charakterystyka zmienno�ci opadów atmosferycznych na Kop- ciowej koło Krynicy Zdroju w latach 1971-2000. Acta Agr. et Silv., ser. Silv. 40: 5–16. Kowalski T. 2003. Endophytic fungi: V. Mycobiota in living leaves of Acer pseudoplatanus and in necrotic tissues around galls of Drisina glutinosa. Phytopath. Pol. 29: 23–35. Lang K. J. 2000. New hosts of Cristulariella depraedans. For. Path. 30: 117–120. Mańka K. 2005. Fitopatologia le�na. PWRiL. Warszawa. Mirek Z., Pięko�-Mirkowa H., Zając A., Zając M. 2002. Flowering plants and pteridophytes of Poland. A checklist. W. Szafer Institute of Botany, Polish Academy of Sciences, Kraków. Redhead S. A. 1975. The genus Cristulariella. Can. J. Bot. 53: 700–707. Cristulariella depraedans 11 Redhead S. A. 1979. Mycological observations: 1, on Cristulariella; 2, on Valdensenia; 3, on Neolecta. Mycologia 71: 1248-1253. Saccardo P. A. 1908. Notae Mycologicae. Series X. Ann. Mycol. 6: 553–569. Saramak A. 2005. Opady atmosferyczne w Gaiku-Brzezowej w latach 1971-2000. (In:) E. Bogdanowicz, U. Kossowska-Cezak, J. Szkutnicki (eds). Ekstremalne zjawiska hydrologiczne i meteorologiczne. Polskie Towarzystwo Geofizyczne IMGW, Warszawa: 184–197. Skrzypczyńska M. 2004. Studies on the population frequency of insects and mites causing galls on the leaves of the sycamore maple Acer pseudoplatanus L. in southern Poland. J. Pest. Sci. 77: 49–51. Sydow P. 1912. Mycotheca Germanica. Fasc. XXII–XIII. Ann. Mycol. 10: 445–451. Trolinger J. C., Elliott E. S., Young R. J. 1978. Host range of Cristulariella pyramidalis. Plant Dis. Reporter 62: 710–714. Willetts H. J. 1997. Morphology, development and evolution of stromata/sclerotia and macroconidia of the Sclerotiniaceae. Mycol Res. 101 (8): 939–952. Wulf A. 1990. Über die Bedeutung von Diplodina acerina (Pass.) Sutton und anderen Blattpilzen als Antagonisten der Fenstergallmücke Dasineura vitrina Kffr. an Bergahorn (Acer pseudoplatanus L.). Nachrichtenbl. Pflanzenschutzd. 42: 97–102. Wulf A. 1994. Pilzbedingte Blattkrankheiten an Ahorn unter besonderer Berücksichtigung des Berg- ahorns (Acer pseudoplatanus L.). Schriften aus der Forstlichen Fakultät der Universität Göttingen und der Niedersächsischen Forstlichen Versuchsanstalt. 116: 46–58. Cristulariella depreadens jako sprawca plamisto�ci li�ci klonów oraz innych drzew i krzewów S t r e s z c z e n i e Badania prowadzono w okresie 1996-2006 na terenie Ojcowskiego PN, Tatrzańskiego PN, Nadl. Świerklaniec i w Lesie Wolskim koło Krakowa (Tab. 1). W okresie od lipca do paździer- nika, z 30 powstałych zwykle w wyniku samosiewu młodych drzew oraz dolnych partii koron drzew starszych Acer pseudoplatanus i A. platanoides pobierano 1 – 3-krotnie 30 do 60 li�ci wykazujących różne objawy chorobowe oraz po 3 do 6 li�ci z objawami chorobowymi dwu- dziestu innych gatunków drzew i krzewów rosnących w sąsiedztwie badanych klonów (Tab. 2). W laboratorium dokonywano analizy nekroz i oznak etiologicznych C. depraedans. C. depraedans stwierdzony został we wszystkich czterech rejonach, gdzie pobierano ma- teriał do badań, przy czym na terenie Nadle�nictwa Świerklaniec C. depraedans występował tylko sporadycznie. Na terenie Tatrzańskiego PN, Nadl. Świerklaniec i w Lesie Wolskim C. depraedans stwierdzono tylko na li�ciach Acer pseudoplatanus, natomiast w Ojcowskim PN na obu badanych gatunkach klonów oraz na 8 innych gatunkach drzew i krzewów: Carpinus betulus, Cornus sanguinea, Corylus avellana, Fagus sylvatica, Lonicera xylosteum, Padus avium, Quercus robur i Tilia cordata. Na 12 innych gatunkach drzew i krzewów rosnących w sąsiedz- twie porażonych klonów nie stwierdzono objawów porażenia przez C. depraedans (Tab. 2). Występowały pewne różnice w objawach porażenia zarówno pomiędzy A. pseudoplatanus i A. platanoides, jak i pomiędzy pozostałymi gatunkami ro�lin. Na jednym li�ciu A. pseudopla- tanus występowało od 9 do 438 nekroz. Osiągały one do 22 mm �rednicy (Tab. 3). Pojedyncze nekrotyczne plamy były prawie okrągłe, w czę�ci �rodkowej szarobiałe, w czę�ci przyobwodo- wej ciemnoszare (Tab. 2; Figs 1, 2). Na jednym li�ciu A. platanoides występowało do 338 lokal- nych nekroz (Tab. 3). Oprócz nekroz małych 1 do 5 mm �rednicy, obecne były nekrozy do 33 mm �rednicy (Tab. 3; Fig. 3). Nekrotyczne plamy miały barwę jasnoszarą do jasnobrunatnej w czę�ci centralnej, oraz ciemnoszarą lub brunatnoszarą w strefie graniczącej z tkankami ży- wymi. Li�cie pozostałych gatunków ro�lin porażone były przez C. depraedans w różnym stop- niu. Najwięcej nekrotycznych plam stwierdzono na li�ciach Cornus sanguinea i Quercus robur, odpowiednio do 582 i do 286 plam (Figs 7, 9). Średnica nekrotycznych plam u ro�lin spoza rodzaju Acer wahała się w granicach od 1 do 6 mm (Tab. 3). U wszystkich gatunków ro�lin 12 T. Kowalski and Cz. Bartnik nekrotyczne tkanki wykazywały mniej lub bardziej wyraźne różnice w zabarwieniu pomiędzy czę�cią �rodkową i przyobwodową (Tab. 3). Propagule miały postać kulistej lub lekko spłaszczonej względnie nieco wydłużonej, wielo- komórkowej główki o �rednicy 60 do 140 µm osadzonej na septowanym, hyalinowym trzonku o długo�ci 120–180 µm i grubo�ci 10–15 µm. Figs 1-4. 1. A young sycamore (A. pseudoplatanus) with symptoms of infection by C. depraedans on all leaves in the crown; 2. A leaf of A. pseudoplatanus with numerous necrotic spots caused by C. depraedans; 3. A leaf of A. platanoides with numerous necrotic spots caused by C. depraedans; 4. A leaf of A. platanoides with the local lesions of different size resulting from different infection times by C. depraedans. 1 3 2 4 Figs 5-9. 5. Propagules of C. depraedans on the underside of a leaf lesion on A. platanoides; 6. Propagulas of C. depraedans (magnified); 7. Leaves of Quercus robur with symptoms of infection by C. depraedans; 8. Leaf developed on sprout of Carpinus betulus with symptoms of infection by C. depraedans; 9. Leaf of Cornus sanguinea with symptoms of infection by C. depraedans. 5 7 8 9 6 2014-01-01T11:46:53+0100 Polish Botanical Society