484 Fini(j{ci(f<(/ Propcrtioi of Certain Sprdij-Fla'ulfi 



Gooseberries. 1915. 



For the purpose of ascertaining the efiect of a caustic soda spray 

 upon Gooseberry foliage, a solution of 1-5 % was used on the leaves of 

 two varieties of Gooseberry, viz. Yellow Hough and liancashirc Lad. 

 On Yellow Rough it produced by the first day " scorching " in the form 

 of iiiinuto, black patches on the youngest leaves only ; the extreme 

 tip of one shoot was killed. On the fourth day some of the older leaves 

 showed patches of a brown discoloration and also brown edges; by 

 the tenth day a severe defohation had occurred. On Lancashire Lad 

 by the first day the youngest leaves only showed "scorching" in the 

 form of minute black patches; on the fourth day some of the older 

 leaves showed brown edges, and by the tenth day a few of the leaves 

 had fallen. 



Summary of Observations. IL 



Caustic soda was not tried at a lower concentration than 0-3 %. 

 At this strength it has an immediate injurious action on the mildew 

 and at the same time kills the epidermal cells at the periphery of the 

 mycehum of the mildewed patch. The action is not powerful enough, 

 however, at this concentration, nor at the increased concentration of 

 0-5 %, to kill the mildew, and we find that the mildew recovers gradually 

 until by the ninth to thirteenth day after treatment many of the 

 patches are again powdery with conidia from fresh conidiophores. 



Serious injury to the leaf (apart from the portion occupied by the 

 mildew) has been observed at a concentration of 0-75 % which almost 

 prohibits the use of such a solution. At 1 % the mildew is usually 

 killed and the tip of the leaf is usually "scorched" and killed. In 

 Exper. 7 (recorded above), in which the three mildewed leaves w-ere 

 sprayed on both sides with a 1 % solution, all the patches of mildew 

 were killed very satisfactorily and this was accompanied by the death 

 of the leaf-cells underlying and surrounding each patch. Distinct 

 "scorching" injury was produced to the tip of the leaf and adjacent 

 margin. 



At the contentration of 1-5 % the risk of serious leaf-injury is so 

 great as to prohibit the use of such a solution. In Kx|)or. 10, the older 

 leaves were very seriously scorched by a 1-5 % solution and while the 

 younger leaves showed only injury at the tip, it was found that this 

 so damaged them that they could not develop properly. In one experi- 

 ment (not recorded above) twelve hop plants, bearing numerous patches 



