JOURNAL OF FOREST SCIENCE, 50, 2004 (7): 319–326 Dothistroma needle blight Mycosphaerella pini E. Rostrup, a new quarantine pathogen of pines in the CR L. JANKOVSKÝ, M. BEDNÁŘOVÁ, D. PALOVČÍKOVÁ Faculty of Forestry and Wood Technology, Mendel University of Agriculture and Forestry, Brno, Czech Republic ABSTRACT: Dothistroma needle blight caused by Mycosphaerella pini E. Rostrup was observed for the first time in the Czech Republic on an imported Pinus nigra Arnold in 1999. In 2000, it was also found in the open planting. During three years, it became an important pathogen of pines in the Czech Republic. Its occurrence was noticed in more than 50 localities, above all in the region of Moravia and Silesia and eastern Bohemia. In total, it was found on 10 species of pine (P. nigra Arnold, P. banksiana Lamb., P. contorta Loudon, P. mugo Turra, P. leucodermis Ant., P. sylvestris L., P. cembra L., P. aristata Engelm., P. ponderosa P. et C. Law- son and P. jeffreyi Grev. et Balf.). Also Picea pungens Engelm. was noticed as a host species. In the Czech Republic, Pinus nigra is the most frequent host species of M. pini (80% localities) followed by Pinus mugo (27% localities). On Scots pine P. sylvestris, M. pini was noticed at two localities. The critical period for infection is in the Czech Republic from the second half of May until the end of June. The incubation period lasts about 2–4 months depending on climatic conditions. The first symptoms on the needles infected in the current year appear in August being clearly expressed from September to November. In the CR, Dothistroma needle blight spread probably with infected planting stock obtained from import at the end of the 80s and at the beginning of the 90s. Keywords: Dothistroma needle blight; Mycosphaerella pini; Dothistroma septospora; Pinus; needle cast; quarantine pests; Picea pungens Dothistroma needle blight is caused by the fungus My- stroma needle blight has become one of the most impor- cosphaerella pini E. Rostrup apud Munk (syn. Schirria tant diseases of pines worldwide. At present, it is a com- pini Funk & Parker). It is also known by its asexual state mon pathogen in North America, South America, Central name Dothistroma septospora (Dorog.) Morelet (syn. America, Africa, Asia, Oceania and Europe. Dothistroma Dothistroma pini Hulbary). It is one of the best known needle blight is now distributed worldwide, and has been and most studied needle casts of pines and has caused reported in at least 45 countries (BROWN et al. 2003). extensive damage and defoliation of pines in many parts In most cases where this disease has imparted serious of the world (GIBSON 1972). The pathogen is native on losses, the pathogen has been introduced; optionally the pines in the northern hemisphere and was first recognized hosts have been planted outside of its natural environment. and described from Europe in 1911 (GIBSON 1972) but it M. pini was reported from 12 tropical countries, especially prefers subtropical regions and mountain regions of the from derelict research plots and abandoned plantations tropics. The origins of the pathogen are unclear. IVORY (IVORY 1994). In some mountain regions of subtropics (1994) suggested that Dothistroma pini has been found and tropics, it is a limiting factor for growing pines. to be indigenous to pine forests in Nepal, and it may be A particularly susceptible species is the commercially endemic in the Himalayas. Alternatively, it is supposed most distributed species Pinus radiata D. Don. that the needle blight originates from mountain regions Dothistroma needle blight affects many species of coni- of Central America (Honduras, Guatemala) at altitudes fers, but 2-, 3- and 5-needled pines are the most common 1,600–2,200 m. The early reports described the fungus hosts. Apart from pines, other coniferous species such as both in Europe and the USA prior to the 1920s, although European larch (Larix decidua), Norway spruce (Picea it was not recognized as a serious pathogen until the 1960s abies), sitka spruce (Picea sitchensis) and Douglas fir (BRADSHAW et al. 2000 in BROWN et al. 2003). Together (Pseudotsuga menziesii) are occasionally susceptible. with the development of market with planting stock, rapid In total, over 60 pine species are reported to be prone to spread of the needle blight occurred. Thus, the Dothi- infection (BROWN et al. 2003). Supported by the Ministry of Education, Youth and Sports of the Czech Republic, Project No. MSM 434100005. J. FOR. SCI., 50, 2004 (7): 319–326 319 In Europe, Dothistroma needle blight occurs above all similarly as in case of an attack by more common blights in countries south of the Czech Republic (Croatia, Italy, Lophodermium pinastri (Schrad.) Chev. and L. seditiosum France, Hungary, Spain, France, Switzerland, etc.). In the Minter, Staley et Millar. The phenomenon is conspicuous Czech Republic, the first record originates from Pinus ni- in the course of April to June. At that time, it is possible gra Arnold imported from Hungary in 1999. In plantings to find verrucose formations on last year’s needles and in the open, it was observed at the first time in the planta- needles formed in the year before last. Under the forma- tion of Christmas trees Pinus nigra Arnold near Jedovnice tions, subepidermal acervuli are formed. about 30 km north of Brno in May 2000 (JANKOVSKÝ et al. The aim of the paper is to evaluate the present occur- 2000). At that time, it was already known from a number rence, the host spectrum, symptomatology and bionomy of European countries including Austria (PETRAK 1961), of the needle blight in the region of the CR. France (in 1966; VILLEBONE, MAUGARD 1999 in BROWN et al. 2003), Slovenia (MACEK 1975), Germany (BUTIN, MATERIAL AND METHODS RICHTER 1983), Poland (KOWALSKI, JANKOWIAK 1998) where it was found in May 1990, Slovakia (KUNCA, FOF- Within monitoring carried out in 2000–2003, pine nee- FOVÁ 2000) and Hungary (KOLTAY 1997). dle samples were examined taken mainly in the region During a relatively short period, Dothistroma needle of southern and central Moravia, Silesia and eastern and blight was detected on a number of localities and as com- central Bohemia. Individually also from other regions of pared with the original expectation it became one of the the CR. Samples were taken with symptoms of damage most important quarantine organisms in the CR. In the to the assimilatory apparatus of pines. course of three years, a number of focuses was noticed Mycosphaerella pini was detected on the basis of the oc- above all in the region of Moravia, Silesia and eastern currence of external symptoms of infection and according Bohemia. to morphology of fructification organs. The host spectrum Mycosphaerella pini E. Rostrup (syn. Scirrhia pini Funk and dynamics were studied of the development of infec- et Parker), anamorph Dothistroma septospora (Dorog.) tion symptoms in the course of the year. Morelet, syn. Dothistroma pini Hulbary, Cytosporina Specimens are deposited in the herbarium of the De- septospora Dorog. was rearranged to a new genus Erup- partment of Forest Protection, Faculty of Forestry and tio as Eruptio pini (Rostr. apud Munk) M. E. Barr (BARR Wood Technology, Mendel University of Agriculture and 1996) in 1996. This new name is not usual in phytopatho- Forestry Brno (BRNL). logical literature and a former classification into the genus Mycosphaerella is used so far. However, using a name RESULTS AND DISCUSSION for the anamorphic stage of Dothistroma septospora is more exact, when a teleomorphic stage is very rare being Symptoms of M. pini infection under conditions unknown in some regions. in the CR The most common symptoms of Dothistroma needle blight are red strips on needles where acervuli are formed Typical manifestations related to needle dying of the amounting to 1–30 per needle. Their vicinity is character- lower part of a crown and the abundant occurrence of red ized by more or less marked terracotta colouring. Conidia strips on dead tissues of needles were noticed in the CR are filamentary at length with 1–5 (7) partitions and 8–32 primarily on Austrian pine Pinus nigra. Typical symp- (40) × 2–3 µm in size. On the basis of variability of co- toms were, however, also formed in other pines, viz. P. nidia a number of varieties was described. Ascospores are banksiana Lamb., P. contorta Dougl. ex Loud., P. aristata hyaline, bicellular, obtuse-rounded, 7.5–14 × 2–3.5 µm in Engelmann etc. Dying the needle tips shows markedly in size. In addition to typical articulate conidia, spermogonia susceptible P. ponderosa and particularly P. jeffreyi. of Asteromella synanamorph are also formed 3 × 1 µm Dwarf pine Pinus mugo gets dry in the whole crown in size. Ascospores are noticed only exceptionally; from and, therefore, it is not possible to differentiate the attacked a number of regions, teleomorphic fruit bodies are un- lower third as in Pinus nigra. Thus, the typical needle tip known. dying is not so evident. Rusty strips are rather formed on Infection permeates into plants through stomata. Incu- needles. The strips then enlarge and acervuli begin to form. bation time differs according to local conditions. While Characteristic red strips occur only on quite dead needles. under conditions of subtropics the time can take 6 weeks, On Swiss stone pine Pinus cembra var. sibirica L. from under European conditions incubation lasts 3–6 months. Kunovice locality, a typical dying of needle tips, forma- Dothistroma needle blight is most frequent in plants, tion of acervuli and drying the lower part of a crown oc- young plantations and particularly in Christmas tree plan- curred at the end of March 2003. Similarly as on Pinus tations until about 10–20 years of age.