APPLE DISEASES 129 
turns brown, the cells collapse, and the canker shows a sunken 
surface. If the atmosphere is continuously humid, conidial 
tufts arise from the mycelium. From these tufts, conidia are 
liberated; they are then carried to other points where new 
cankers are formed. The mycelium grows more rapidly parallel 
to the long axis of the limb and hence the canker is the longer in 
this direction. Where the wood is entered, the mycelium in- 
vades the sap-tubes in which it passes up and down. It is be- 
lieved that at points above and below the canker the fungus 
again attacks the cortex, this time from within, thus forming a 
new canker without direct external inoculation. About a year 
after the canker starts to develop the mycelium forms the red 
perithecia. These may act as a means of carrying the fungus 
through the winter. 
Control. 
The chief measures to be used against the European canker 
are those of eradication as outlined for the black-rot canker 
(page 52). The smaller limbs and the badly diseased larger 
branches should be wholly removed. Smaller cankers on large 
valuable limbs and on trunks should be cut out, the upper and 
lower ends of the wound pointed, and finally a wound-dressing, 
preferably coal-tar, should be applied. 
REFERENCES 
Weese, J. Zur Kenntnis der Erregers der Krebskrankheit an den 
Obst- und Laubholzbaumen. Osterreich. landw. Versuchw. 
Zeitschr. 1911: 872-885. 1911. 
Hartig, R. Der Krebspilz der Laubholzbiume. Untersuchungen aus 
dem forstbotanischen Institut zu Miinchen, pp. 109-125. 1880. 
Goethe, R. Weitere Mittheilungen tiber den Krebs der Apfelbiume. 
Landw. Jahrb. 9: 837-851. 1880. 
Aderhold, R. Impfversuche mit Nectria ditissima Tul. Centbl. f. 
Bakt. 2: 10: 763-766. 1903. 
Lapine, N. Der Krebs der Apfelbaume. Landw. Jahrb. 21: 937- 
949. 1892. 
Brooks, Charles. Some apple diseases. European apple canker. 
New Hampshire Agr. Exp. Sta. Bul. 144: 128-129. 1909. 
K 
