202 FUNGOUS DISEASES OF PLANTS 



XI. LARCH CANKER 



Dasyscypha Willkommii Hartig. 



HARTIG, R. Die Larchenkrankheiten^ insbesondere der Larchenkrebspilz. 

 Untersuch. aus d. Forstbotan. Institut Miinchen 1 : 63-87. 1880. 



Occurrence and effects. The larch canker is one of the most 

 important diseases of this host in certain districts of Europe. It 

 is particularly abundant in the moist, marshy, mountain meadows, 

 but is seldom of importance on hillsides or slopes. The fungus 

 is a typical canker-producing organism, and, so far as is known, it 

 gains entrance to the host only through wounds. It spreads most 

 rapidly in the phloem elements and rapidly causes the death of 

 the bark. The diseased areas become shrunken and brown. The 

 bark may peel away in places and pronounced cankers develop. 

 The fungus appears to spread rapidly only during seasons when 

 the host plant is comparatively inactive, as during the autumn 

 and winter. The wounds of the previous year may, therefore, 

 be practically healed over during the growing season, but the 

 following autumn the fungus continues its spread, and in time 

 large limbs or trunks may be completely girdled and death result. 

 The needles on affected twigs begin to show the presence of the 

 fungus during the late summer. 



The fungus. Upon the death of the bark the fungus appears 

 superficially in the form of creamy or yellowish-white stromatic 

 tufts. Upon the minute conidiophores there are produced simple 

 hyaline conidia. The latter have not been germinated and do not 

 appear to be important in the immediate distribution of the fungus. 

 Later in the season the apothecia may appear on the diseased areas 

 if there is sufficient moisture. The apothecia are short stalked, 

 almost sessile, yellowish without, and orange colored within. The 

 asci measure about 1 20 x 9 /LI. They are cylindrical in form and 

 contain invariably eight ovoidal, unicellular spores. Between the 

 asci are interspersed a considerable number of filiform paraphyses. 

 Inoculation experiments have demonstrated that this fungus is the 

 cause of the canker with which it is associated. No preventive 

 measures can be recommended when the fungus is once estab- 

 lished on larch plantations, and, therefore, in locating new planta- 

 tions, one should bear in mind the conditions under which the 

 fungus is most disastrous. 



