80 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



Top Canker of Spruce and Pine 



E. Bjorkman 

 Dean, Royal School of Forestry, Stockholm, Sweden 



Scleroderris lagerbergii (Lagerb.) Gremmen. A parasite on Pinus 

 in western Europe and on Picea mainly in Scandinavia. The identity 

 of this fungus was elucidated by Lagerberg in 1913 when, among other 

 things, earlier confusions with Cenangium ferruginosum Fr. were ex- 

 plained, and the pycnidial stage of the fungus, which had been de- 

 scribed as Brunchorstia pinea (Karst.) v. Hohn, was classified under 

 the specific name Crumenula abietina,. This species has later been 

 described by Gremmen and van Vloten in 1953 as Scleroderris abietina 

 (Lagerb.) Gremmen, and by Gremmen in 1955 as Scleroderris lager- 

 bergii (Lagerb.) Gremmen. Some other synonyms are: Crumenula 

 pinea (Karst.) Ferd. & Jorg., and for the pycnidial stage Brunchorstia 

 destruens Eriksson. 



The fungus generally attacks young spruce, but under epidemic 

 conditions may sometimes appear also on older individuals. The 

 damage is generally discovered when the tops of the spruce die and, 

 on a more close investigation, a wound or a clear zone between the 

 living and the dead tissue on the top shoot of the year before is found. 

 The infection will therefore probably take place on the top shoot itself, 

 but it is first in the following year that the supply of nutrition is cut off 

 causing the top of the spruce to die. A heavy resin flow appears near 

 the zone between living and dead tissue where also the reproduction 

 stages will be found. 



The pycnidia are black, hemispherical, and 0.2 to 1.5 mm. in diam- 

 eter. The apothecia are easily confused with the pycnidia, being about 

 1 mm. in diameter, but are as a rule recognized by their flat or concave 

 tops. Through burstings in the pvcnidium wall, the spores are pressed 

 out. especially in wet weather. The spores are sickle-shaped with 2 to 

 6 cells (generally 4) and of varying size. Lagerberg estimates spore 

 size to vary between 4 X 43/x and 3 X 22/*. The spores germinate easily 

 in water. The asci are elongate without an apparent stem, 100 X 160^ 

 and 9 X 15/x. The ascospores are fusiform with 4 cells. In typical cases 

 the size will be 15-24/a and 4-6/x. The spores also germinate easily 

 in water, even if still enclosed in the asci. 



Spruce tops may be much deformed by the fungus ; after a couple 

 of years, however, the results of the damage will as a rule disappear. 

 The fungus can be considered as being of relatively little importance 

 as far as the spruce is concerned. 



On Pinus the species has been described as "bud-drought," as it is 

 the buds on the fully grown shoots that are attacked and then do not 

 shoot in the following spring. This stage can develop into a "branch- 

 drought." Especially on pines imported to Sweden it can have a 

 quite devastating effect. The fungus has broadly been described in 

 this way by Lagerberg, but it has never been necessary to reckon 

 with very heavy damages on Pinus sylvestris. 



In 1958, however, this fungus also started attacking 1-year-old and 

 especially 2-year-old seedlings in a great number of nurseries in north- 

 ern Sweden, and millions of seedlings were killed. Shoots and buds 

 are infected during all summer and autumn, first through conidia and 



