H. WORMALt) 199 



pruned in autumn in the usual way and no special instructions with 

 regard to the disease has been issued to the men entrusted with the 

 work. The consequence was that although a certain amount of "dead 

 wood"' had been cut away a considerable number of spurs and cankers, 

 which subsequently produced the conidial stage of the fungus, remained 

 on the trees. In some cases a dead spur had been cut ofE close to the 

 branch but the diseased tissues of the canker round the base had been 

 left and later the fungus appeared there. In the spring of 1916 it was 

 found that every tree bore the fungus in its infectious (conidial) con- 

 dition, the number of dead spurs and cankers with pustules varying 

 from one to twenty-five per tree with an average of eight. The number 

 of wilting trusses on these trees in May 1916 was 159 and varied from 

 two to twenty- nine per tree ; these numbers would probably have been 

 considerably higher but for the fact that the trees had produced that 

 year exceptionally few trusses of bloom. On several trees however 

 more than one-fifth of the trusses wilted and in one case more than 

 half of those present were killed. 



Thus on those trees from which all dead spurs had been removed 

 (omitting the one on which two had been overlooked) the number of 

 wilted trusses was reduced, on the average, to less than one per tree, 

 the infection in these cases being doubtless due to air-borne conidia 

 from the infected trees in the rest of the row, while those trees on which 

 infected spurs were left had an average of eleven wilted trusses per 

 tree. 



The ideal mode of treatment would be the removal of diseased 

 trusses immediately after they first show signs of wilting; this would 

 involve examining the trees three or four times at intervals of about a 

 week between one examination and the next, all wilting trusses being 

 removed and the spurs cut back until all brown bark and wood is 

 removed, the first of these operations to be done about fourteen days 

 after the earliest flowers open. This method would prevent the develop- 

 ment of cankers which are not only much more troublesome to remove 

 than the spurs themselves but it would prevent the girdling and death 

 of the small branches. 



As such measures would usually be impracticable except in small 

 plantations of bush trees where the disease has not yet become rampant, 

 an alternative would be to prune off all diseased spurs and cut out the 

 cankers as occasion permitted during the summer. This work should 

 be done as early as possible for the dead trusses with their withered 

 brown leaves are easily distinguished from the healthy ones and clearly 



