3o6 DISEASES OF CROP-PLANTS 



of the cane, extending from one or both ends, so that when a 

 cutting is split open it shows a blackened core, around which the 

 tissues may retain their normal colour or be somewhat reddened. 

 The smell is often an aid in diagnosis, being distinctly more fruity 

 than that of merely sour cane. 



Attacks on standing cane are comparatively seldom noticed. 

 Their occurrence is favoured by wet weather. There is the same 

 blackening of the tissues as in cuttings. The fungus is un- 

 doubtedly capable of parasitism and may extend to a considerable 

 distance up and down from the original point of entry. 



In the case of cuttings there is no difficulty about entrance ; 

 in standing canes it occurs most commonly by way of borer 

 holes, but may take place through the leaf scars. 



Loss of cuttings from this disease usually occurs when owing 

 to the prevalence of dry weather they remain a long time in the 

 ground before springing. In such an event the fungus has time 

 to destroy the whole cutting and the loss of a planting may be 

 complete. There is no evidence of varying resistance in different 

 cane varieties, though it is a matter of common experience that 

 these differ greatly in their germinating capacity. 



Control. 



The standard measure for the protection of cuttings against 

 infection is to dip or soak them in Bordeaux mixture, and im- 

 proved germination has on occasion been secured by this treat- 

 ment. On the other hand many disappointments have been 

 experienced when the measure has, nominally at least, been 

 adopted. When the weather is favourable - the treatment is 

 not found to be necessary, but since this cannot be depended 

 on it is usually desirable as a precautionary measure. It needs 

 to be pointed out to planters, however, that dipping has no 

 ceremonial value, so that unless, after the cutting has been 

 handled, placed in the ground, and covered in, there remains 

 on its ends a well-distributed fihn of blue sediment, the benefits 

 of the process will be looked for in vain. Nor must it be expected 

 to give protection if the ends of the cuttings are split or ragged. 

 Dipping the ends in gas tar has been advocated as affording 

 a more adhesive coating, but it is difficult to apply on a large 

 scale and most planters will prefer to take chances, as indeed 

 many do rather than trouble with the comparatively simple 

 Bordeaux treatment. 



The method commonly in use in applying Bordeaux mixture 

 is to prepare it in a tank or hogshead and soak the cuttings 

 either loose or in bags. There is no virtue in soaking and the 

 crystallization of the precipitate after standing makes it less 

 adhesive. The points that are of importance are (i) the prepara- 

 tion of a mixture with a finely divided and adhesive precipitate 

 and its use while fresh, (2) the agitation of the mixture so that 



