252 EXPERIMENTAL FARMS 



2 GEORGE V., A. 1912 



living through the winter in these affected twigs and growing out into the leaves the 

 succeeding spring. It is now known, however, that the mycelium very rarely lives 

 over and that almost all infection takes place from outside as the leaves unfold. 



The relation between this disease and climatic conditions is well known. The 

 severity of an attack is much increased by cold, damp weather at the time the buds 

 are bursting. The slower the development of the leaf, the longer it is in getting 

 beyond the susceptible stage, whilst excess of moisture in the tissues also seems to 

 directly favour the fungus. 



Control. 



There are few diseases which respond so readily to proper spraying treatment. 

 It has been well established that one application of a suitable spray-mixture completed 

 before the buds begin to swell, will practically control the disease. For this purpose 

 the lime-sulphur mixture, either the home-boiled or the commercial, is recommended, 

 since it is not only thoroughly effective against the fungus but is also an insecticide. 



bacterial blight of English walnut (Juglans Eegia L.) (bacterium {Pesudomonas] 



Juglandis, Pierce). 



This disease was observed at Agassiz, B.C., in the grounds of the Experimental 

 Farm. Nearly all the walnut trees were affected and the nuts produced were practi- 

 cally all rendered useless. The injury manifested itself on the leaves by the produc- 

 tion of more or less large brownish areas of dead tissue; the fruits also showed black- 

 ish spots or they had turned quite black. The shell, generally hard in sound fruits, 

 was soft in attacked ones and the kernel had turned black and putrid. Young twigs 

 also showed signs of the disease. They had died back for a distance of about a foot 

 or more, the wood showing a dark centre for a considerable distance, although no 

 external injury could be observed, with the exception of the dead tips. 



The disease was first investigated by Pierce in Southern California. It is of no 

 little interest to have observed the disease at Agassiz, where it has prevailed for some 

 years. These trees were imported some twenty years ago from France and made quite a 

 satisfactory growth until some years ago when this bacterial blight appeared. In South- 

 ern California, the disease caused serious alarm among the growers, who, at one stage of 

 this disease, offered a reward of $20,000 for a satisfactory remedy, which is another 

 instance of the serious economic importance of plant diseases. The English walnut 

 may easily be grown in the Pacific coast regions as well as in the Niagara district, 

 and the attention of the growers is directed to this outbreak which, in the aspect of 

 its severity and in its cause, is identical with the Californian disease. Trees that 

 have been attacked should be carefully pruned, all dead wood being removed and burned 

 immediately. According to Dr. E. F. Smith, copper fungicides have been found useful 

 in its control, and periodical spraying should be practised. 



DISEASES OF SMALL FRUITS. 



ANTHRACNOSE OF RASPBERRY AND BLACKBERRY (GloeOSporilim Vetietlim, Speg) 



This disease is found on the canes, leaf-stalks, and leaves. It is, however, on the 

 canes that it is most serious. Here it produces purplish spots, which, as they extend, 

 become greyish and depressed in the centre with a reddish border. When the attack 

 is severe, these spots may coalesce in such a way as to ' girdle ' the cane, which then 

 withers and dies. Even where the injury is less marked, the conduction of sap may be 



