35 



of this stock on an extensive scale has only been practised for 

 the last 10 or 12 years. In the case of Victorias it is usually in 

 trees 20-25 years old that Silver Leaf causes such wholesale 

 damage, hence it is too early to form an opinion based on any 

 extensive trial. The, Yellow Pershore plum itself is un- 

 doubtedly occasionally attacked by Silver Leaf, and, according 

 to reliable growers, Victorias worked on it have, after a time, 

 shown signs of the disease. The whole question of stocks is 

 now under investigation both from a scientific and practical 

 standpoint. 



Measures of Control. Although no cure for Silver Leaf 

 is at present known, the following recommendations, if carried 

 out thoroughly, will materially help in checking the spread of 

 the disease : 



1. Removal of Trees and Cutting out Branches. Some 

 growers advocate the removal and destruction of all trees show- 

 ing silvered foliage ; but, judging from experience in Cambridge- 

 shire on a fairly extensive scale, it appears that this drastic 

 treatment is not necessary. If affected trees are systematically 

 and energetically dealt with as soon as the disease appears, it 

 is possible very considerably to control its spread. To effect 

 this the following two operations must be rigorously 

 enforced : 



(a) All dead trees must be grubbed up and destroyed, and 



also all trees which have begun to die back. 



(b) All silvered branches, even though they show no signs 



of dying back must be cut out. It will be remem- 

 bered that the minute threads of the fungus are 

 usually found in the tissues of the wood consider- 

 ably further down the branch than the level at 

 which the silvered leaves appear. Silvered 

 branches, therefore, mnst be cut back to a point 

 where no dark stain in the wood can be found. 

 Unless this be attended to the operation will not be 

 successful and the disease will spread to other 

 branches. It should further be remembered that, 

 as callus-formation takes place much more readily 

 if the branches are cut back flush with the main 

 branch or stem, it is important, if practicable, to 

 cut back in such a manner. 



2. Protection of Wounds. This is exceedingly important. 

 All wounds made by the removal of branches should be pared 

 over with a knife, and covered at once with Stockholm tar. As 

 tar often loses its effect after three months it is necessary, in the 

 case of the larger branches at any rate to renew the tar dressing 

 at frequent intervals. Wounded surfaces made by the breaking 

 off of branches through wind or other causes should be pared 

 and tarred in the same way, and in the case of the highly 



