652 Journal of Agriculture, Victoria. [11 Xov., 1918. 



after the sixth year. The distance between the next circle and the outer 

 one represents the difference between the radius of the circle circum- 

 scribing this specimen and that enclosing Fig. 1. 



In consequence of the sap ceasing to flow in the cambium of the 

 depressions, the bark of these portions, although becoming partly 

 devitalized from the time of infection, usually retains its natural 

 colour, but becomes coriaceous, and adheres firmly to the wood. 

 .Further experiment and observation will probably reveal the 

 cause of the discontinuance of sap circulation in the affected 

 cambium. With most diseases, a diagnosis is necessary before 

 a remedy can be obtained. In 'the case of the gnarl, however, the 

 fairly satisfactory remedial or preventive measures known at present to 

 exist can generally be adopted. 



When trees become affected while young like that illustrated in 

 Plate 180, no time should be lost in removing and replacing them with 

 others propagated in such a manner as to render them less liable to be 

 attacked. In this specimen, photographed at two years old, (a) shows 

 the point where the bud was inserted in ithe l^orthern Spy stock, and 

 the portion of stem between (b) and (c) commenced to gnarl the first 

 year after the yearling whip-growth was planted. Owing to the violent 

 twisting in the wood, this tree would probably have been broken down 

 by the wind before reaching the age of six years. 



Experiments and observation have shown that by careful bud and 

 scion selection, and by the employment of suitable stocks when propa- 

 gating trees, predisposition to unfruitfulness and ordinary variety 

 degeneration may to a great extent be corrected. Much success has 

 been achieved during recent years by working on these lines. 



A considerably higher percentage of Gravenstein trees develop this 

 impediment when worked on Northern Spy in the ordinary way than 

 when grown on their own roots or on seedlings. Nevertheless, owing 

 to tlieir susceptibility to woolly aphis, these stocks cannot be recom- 

 mended for general use. 



A more practical method of coping with the gnarl is to plant some 

 strong growing variety, such as Emperor Alexander, on Spy stocks, and 

 hard pruning for the first two or three years will insure the production 

 of trees of broad and substantial framework. Then the last yearling 

 growths may be budded over or top-grafted with Gravenstein to com- 

 plete the building of the trees. A. tree ^constructed in this manner, 

 the stem, main, and secondary arms constituting the intermediate stock 

 being immune from gnarl, offers a solid foundation to.ihe Gravenstein 

 superstructure, of which only individual branches could suffer by sub- 

 sequent attack. Then, to further reduce the possibility of perpetuat- 

 ing the twisting habit of the wood, only buds and scions of trees free 

 from gnarl should be employed. 



Insect Pests and Fungus Diseases. 



There is no phase in the general routine work of the orchardist's 

 business in which more knowledge of details is required and thorough- 

 ness of individual attention practised than in the case of sprays and 

 spraying. These remarks especially refer to apple-growing, on account 

 of the many insect pests and fungus diseases which infest apple trees 



