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Mycosphaerella dearnessii

Brown spot needle blight
 
Mycosphaerella dearnessii M. E. Barr (anamorphic stage - Lecanostica acicola)
 
Species description:
 

"Brown spot needle blight" causes a similar disease of the assimilative organs of pine trees as Mycosphaerella pini. The pathogen was introduced to Slovakia in the mid-90s of the 20th century.

 Its anamorphic stage is the fungus Lecanostica acicola (Thümen) H. Sydow. However, the sexual stage (teleomorph) of the fungus Mycosphaerella dearnasii Rost. in Munk rarely occurs in our conditions.

Differentiation of individual brown spot needle blights is possible mainly through conidia. The conidia of M. dearnessii are more stocky, slightly curved, 2 - 4.5 micrometers wide. The surface of the conidia is moderately bumpy. It is a dangerous cause of disease of the assimilative organs of conifers.

The first symptoms are pale yellow to brown spots, reminiscent of insect wounds. In November, the infected needles are already brown, and by the end of December, brownish-red spots appear on the browned needles up to the transverse stripes (hence the common name).

 
Bionomy - infection cycle:
Needle infections occur from early May to late September. The disease can be transmitted through raindrops, fog, and wind. The most visible signs of infestation are in May and June when last year's infected needles form warty formations, under which acervuli (asexual fruiting bodies) develop. Subsequently, conidia are released from them, which infect other needles through the spiracles. The infection is partially limited as the acervulus matures at the end of August, and the release of conidia occurs in September.

Pycnids are black lumps that pierce the epidermis and form conidia in the spring. However, the development cycle will not resume until the beginning of next year. After the reproductive formations have overwintered, conidia are released under favorable climatic conditions, mainly sufficient rainfalls and air temperature of 18 to 25 ° C.

Symptom:

The initial signs of infestation include visible light yellow resin-stained spots on the needles, which later turn dark brown. Symptoms of the disease are manifested by the brown transverse spots with yellow edging. The subepidermal somatic acervuli of olive-brown to dark green color form on the dead needles. Subsequently, the infected needles turn brown, wither, and fall off, especially from the tops of the shoots. Repeated occurrences of M. dearnessii over several years can lead to the death of entire trees.
 
Conidia of the fungus. Photo: Foto: H. Ivanová Conidia of the fungus. Photo: H. Ivanová

Infested needles of Scots pine with

fungus Lecanosticta acicola in the area

Stará Lesná. Photo: K. Pastirčáková

 Detail of infested Scots pine needle and conidia of an anamorphic stage of Lecanosticta acicola. Photo:
 K. Pastirčáková

Endangered woody plants:

All species of Pinus spp. are endangered. In our conditions, primarily Scots pine and Mugo pine. The disease occurrence on Picea glauca, Picea omorica, is also reported in the literature.
 

Damaged plant parts: Assimilation organs

 
Significance: Very significant
 
Origin and distribution:
 
Same as Mycosphaerella pini, this pathogen is native to Central America, from where it has spread to other continents. In European countries, it is widespread in Greece, France, Germany, Switzerland, Hungary, Slovenia, Croatia, Macedonia, etc. In Slovakia, the occurrence has been recorded in ​​the Nitra district (Chrenová, Zobor). The anamorphic stage Lecanostica acicola (Thümen) H. Sydow was laboratory-confirmed in the area of ​​Kynek (Nitra district), Stará Lesná (Kežmarok district), Kuková (Svidník district). Another occurrence was recorded in the area of ​​Rimavská Sobota in 2017. 
 
Endangered stands and areas:
 
The whole area of Slovakia is endangered by Mycosphaerella dearnessii, forest stands, and urban vegetation. This species can infect practically all species of pines, and its occurrence has also been reported on spruce Picea omorica, P. glauca. The monocultures of pines in the whole area of Slovakia are potentially endangered.
 
Prevention:
 
It is crucial to prevent transporting the seedlings with visible signs of infestation, brown stripes, and black dots on the needles.
The sufficient spacing during planting has to be preserved. Also, the weed in the plantations has to be removed to avoid favorable moisture conditions suitable for the formation of conidia.
 
Monitoring:
 
Continuously control the symptoms listed above. The most endangered are forest tree nurseries, new plantations, and pine stands up to 20 years.
 
Pest control:
 
Defense methods are used mainly in forest nurseries and plantations of Christmas trees.  It can be applied systemic and also contact fungicides to the pathogen. Spraying should be carried out from the beginning of the growing season (April, May) until autumn. After that, the applications of fungicides must be repeated at 2-3 week intervals, depending on climatic conditions. Prevention is also important, compliance with quarantine regulations, only planting seedlings without signs of attack on assimilation organs.
 
Pest category: Funghi
 

Found in Slovakia: Yes

 

Invasive species: Yes

 

Similar species:

Some species of genus Lophodermium cause similar symptoms on pines in our conditions. One of the identifying features is a brown band and spots on the needles when infested with the fungus Mycosphaerella dearnessii M. E. Barr.

Literature:

Bednářová, M., Palovčíková, D., Jankovský, L., 2006: The host spectrum of Dothistroma needle blight Mycosphaerella pini E. Rostrup – new hosts of Dothistroma needle blight observed in the Czech Republic. Journal of Forest Science 52: s. 30–36.

Butin, H., Richter, J., 1983: Dothistroma need le blight: a new pine disease in the FRG.

Nachrichtenblatt des Deutschen Pflanzenschutzdienstes 35, s. 129-131.

Gibson, I.A.S. (1979)  Diseases of forest trees widely planted as exotics in the tropics and southern hemisphere. Part II. The genus Pinus. Commonwealth Forestry Institute and Commonwealth  Mycological Institute, Oxford and Kew, UK.

Gong, X.D.; Liang, Z.C. (1988) The resistance of slash pine to brown spot needle blight.  Journal of  South China Agricultural University9, s. 54-59.

IMI (1994).

Chandelier, P., Lai-aurie, C; Maugari,F., 1994: Decouverte en France de Myeospbaerella dearnessii sur Pinus attenuata x radiata. C.R. Acad. Agric. Fr. 80, s. 103-108.

Ivanová, H., Bernadovičová, S., 2010: Druhová diverzita mikroskopických húb borovice čiernej rastúcej v urbanizovanom prostredí Nitry. In: Juhásová, G., Adamčíková, K., Kobza, M., Ondrušková, E. (eds.): Dreviny vo verejnej zeleni 2010 : Recenzovaný zborník z konferencie s medzinárodnou účasťou, 22. - 23. 6. 2010 Banská Bystrica. Nitra, Ústav ekológie lesa SAV, Pobočka biológie drevín Nitra. 2010, s. 80-87. ISBN 978-80-89408-08-5.

Jankovský, L., Palovčíková, D., 2000:  Karanténní sypavky Mycosphaerella pini E. Rostrup a M. dearnessii M.E. Barr v České republice.   Lesnická práce. 79, (8), p. s. 370 – 372.

Jankovský, L., Palovčíková, D., 2003: Chrádnutí  borovice černé na Moravě a ve Slezku. Lesnická práce, 82,(3), p. s.  24 – 26. 

Jankovský, L., Palovčíková, D., Tomšovský, M., 2009:  Brown spot nedele blight associated with Mycosphaerella dearnessi occurs on Pinus rotundata ina the Czech Republic. Plant Pathology, 2, p. s. 398.

Kais, A.G., 1971: Dispersal of  Scirrhia acicola spores in southern Mississippi.  Plant Disease

Reporter 55, s. 309-311.

Kais, A., Cordell, C., Affeltranger, C., 1986: Benomyl root  treatment controls brown-spot disease on longleaf pine in the southern United States. Forest Science 32, s. 506-511.

Kapitola, P., Růžička, T., Kroutil, P., 2011: Karanténní škodlivé organismy na lesních dřevinách. Státní rostlinolékažská správa Praha. 63 pp.

Karadzić, D., 1989: Scirrhia pini. Life cycle of the fungus in plantations of Pinus nigra in Serbia. European Journal of Forest Pathology 19: s. 231–236.

Kunca, A., Foffová, E., 2000: Ohrozenie porastov borovice čiernej fytokaranténnym patogénom Dothistroma septopora (Dorog). Morelet. In: Aktuálne problémy v ochrane lesa 2000, zborník z referátov z celoslovenského seminára, 17.–18. apríla 2000 v Banskej Štiavnici, Zvolen, LVÚ Zvolen, s. 136–139.

La Porta N, Capretti P, 2000: Mycosphaerella dearnessii, a needle-cast pathogen on mountain pine (Pinus mugo) in Italy. Plant Disease, 84. p. s. 922.

Petrak, F., 1961: Die Lecanosticta Krankheit der Föhren in Österreich. Sydowia 15: s. 252–256.

Zúbrik, M., Kunca, A., Turčani, M., Vakula, J., Leontovyč, R., 2006: Invasive and quarantine pests in forests in Slovakia. OEPP/EPPO Bulletin 36: s. 402–408.

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