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 Laubholzbaume. Untersuchungen aus 



dem forstbotanischen Institut zu Miinchen, pp. 109-125. 1880. 

 Goethe, R. Weitere Mittheilungen iiber den Krebs der Apfelbaume. 



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. Bui. 144 : 128-129. 1909. 



