11 



stem. (See Leaflet No. 131 Apple and Pear Scab.) These 

 scars frequently allow the entrance of the canker fungus, 

 which causes much more serious damage than the superficial 

 injury of the scab fungus. 



Influence of the Soil. Although the presence of wounds 

 is essential for successful infection by the fungus, there are 

 other factors intimately concerned with the prevalence of 

 canker. Chief among these is the question of location and 

 soil. A variety which cankers in one district may remain, 

 comparatively free in another. Canker is always worse on 

 a low site and a clay subsoil, so much so that it is often 

 impossible in such positions to grow certain varieties of apples 

 successfully (e.g., Lord Suffield, and Cox's Orange Pippin). 

 The effect of damp, heavy soil is to cause rank growth, which 

 probably permits the fungus not only to infect more readily 

 but also to develop more rapidly in the tissues. Although a 

 hill slope and more open soil are desirable much good may 

 be done, where a Bad subsoil is present, by careful drainage 

 and by the encouragement of surface rooting. With improved 

 conditions affected trees will sometimes grow out of canker, 

 and by careful pruning, clean, healthy trees may be produced. 



Susceptibility of Varieties. Another factor of great 

 importance is the nature of the variety, some sorts being 

 exceedingly liable to the disease, whilst others are more 

 resistant. Varieties such as Lord Suffield and Cox's Orange 

 Pippin are so prone to attack that they are liable to canker even 

 on good soil, whilst Bramley's Seedling is resistant and will 

 often remain free even when grown on heavy land. The 

 following varieties are amongst those which under most 

 conditions are subject to attack: 



Cox's Orange Pippin. Peasgood's Nonsuch. 



Dumelow's Seedling (Welling- Pott's Seedling, 



ton). Kibston Pippin. 



Ecklinville Seedling. Stirling Castle. 



Lady Henniker. Warner's King. 



Lord Derby. White Transparent. 



Lord Suffield. Worcester Pearmain. 



Amongst the varieties usually less susceptible may be 

 mentioned : 



Annie Elizabeth. Bramley's Seedling. 



Beauty of Kent. Lane's Prince Albert. 



Blenheim Orange. Mr. Gladstone. 



Bismarck. Newton Wonder. 



Measures of Control. 1. Cutting-out of Diseased Wood. 

 Old and badly -diseased trees should be cut down and burned. An 

 exception to this rule may be made if, as occasionally happens, 

 the trees are bearing well. In the case of trees not so badly 

 diseased, cankered shoots and badly-cankered boughs should 

 be cut out. If a sharp look-out be kept for the commence- 

 ment of the canker, affected branches may sometimes be 

 removed without much loss of symmetry to the tree. During 

 winter-pruning all infected shoots should be carefully removed. 



