Larch and Spruce Canker. 



consisting entirely of females, then migrating to the larch. 

 Under the circumstances a mixture of spruce and larch is not 

 to be recommended, as it furnishes the aphis with its two 

 necessary host- plants. 



As a safeguard against inoculation taking place through bark 

 fissures caused by late frosts, it is advisable not to form seed- 

 beds nor to plant larch in low-lying damp localities, where not 

 only are the plants most exposed to frost, but such situations 

 also favour the presence of the aphis. 



In the case of larger trees there is no cure. If the trunk is 

 not seriously injured the tree may continue to grow and make 

 wood for many years after being cankered. However, it is very 

 important to remember that the toleration of canker-bearing 

 ascophores is a serious menance to surrounding trees. As the 

 spore is the only known means of transmitting the disease from 

 one tree to another in a state of nature, therefore, whenever 

 practicable, all canker wounds should be cut away, and the 

 removed portions burned. Protect the cut surface with a 

 coating of gas-tar. 



In this country ascophores of the fungus are formed every- 

 where in abundance, independent of altitude. 



Literature Quoted. 



1. Hartig, R., Unters. Fprst bot. Inst. Munch: I., p. 63. 



2. Carruthers, J. B., Journ, Roy. Agric. Soc, Ser. III., Vol. II., 



p. 299 (1S91). 



3. Willkomm, M., Die mikroskopischen Feinde des Waldes,. 

 Heft. II., p. 167 (1867). 



4. Ward, H. Marshall, Timber and Some of its Diseases. 

 London (1889). 



5. Buckton, G. B, Mon. British Aphides, Vol. IV., Pl.CXIX., 

 Fig. 4. 



6. Anderson, A. P., Bull. Torrey Bot. Club, v. 29, p. 23 

 (1902.) 



7. Wagner, G. Zeitschr, Pflanzenkr., VI., p. 321 (1891J. 



8. Somerville, W., Report on the Inquiry conducted by the 

 Society into the Disease of the Larch. Trans. Engl. Arboric. 

 Soc. II., p. 363 (1893—94). 



