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



Guignardia aesculi. Perithecia: 80 to 170/*, Asci 54^-70 X 15-17/u, 

 big, ascopores elliptoidic 12-18 X 7-9/x big. 



Control measures. — Collecting and burning the infected leaves in 

 autumn. Breeding of resistant species. 



Range : Europe, America. 



Hosts: Aesculus hippocastanum — 

 A. glabra 

 A. pavia 



Literature : 



Petrak, F. Uber ein verheerendes Auftreten der Blattrollkrankheit 

 der Rosskastanie in der sudlichen Steiermark. Sydowia, Ann. 

 Mycol. Vol. X (1-6) : 264-270. 1956. 

 Stewart, V. B. The leaf blotch disease of horse chestnut. Phyto- 

 pathology VI : 5-19. 1916. 



Snow Blight of Pines 



Phacidium infestans Karst. (German term : Weisser Schneeschim- 

 mel an Nadelholzern. ) In Austria every year heavy damage is done 

 by avalanches, including the death of many people. For this reason 

 an effort is made to afforest the steep slopes with Pvrms cembra L. 

 Whereas the snow melts quickly on the southern slopes, it takes a very 

 long time for the northern slopes to become free from snow. The slow 

 melting of the snow creates good living conditions for the fungus 

 Phacidium infestans which infects the young Pinus cembra. Accord- 

 ing to the size of the tree it impedes growth and development and may 

 even cause death. As Bjorkman ascertained (1942 and 1948), this 

 fungus is able to grow actively under a covering of snow at a tempera- 

 ture of minus 5° Celsius. The significance of this fungus as the patho- 

 genic agent for P. cembra in Austria was discovered in 1955. 



The fungus was first described in 1886 by Karsten, who found it in 

 Finland. Until now this fungus has been lound only on pine trees 

 in the northern parts of Europe, Asia, and America. The infection 

 of the trees takes place through the needle stomata in autumn. The 

 first pathological symptoms can be seen in spring as soon as the thaw 

 has started. The needles become brownish. Under the influence of 

 the sunlight they take on a paler color in summer and become greyish 

 toward autumn. The needle cast does not take place the first year 

 after infection. The apothecia do not develop before July, by which 

 time small black dots can be seen on the needles. The apothecia are 

 not fully grown till October. 



Control measures. — No practical controls known. 



Range : Europe, America, Asia. 



Hosts: Pines 



Literature: 



Bjorkman, E. Kenkulturforsok med snoskyttesvampen {Phacid- 

 ium infestans Karst.) Sv. Bot. Tidskr. 36. 1942 ; 



. Studie over snoskyttesvampens (Phacidium infestans 



Karst.) biologi samt metoder for snoskyttets bekampande. Medd. 

 f. Stat. Skogsforkningsinst. 37, 2. 



Petrak, F. liber Phacidium infestans Karst., einen gefahrlichen 

 Parasit der Zirbelkiefer und einige andere in seiner Gesellschaft 

 wachsende Pilze. Sydowia, Ann. Mycol. IX: 518-526. 1955. 



