﻿430 Proceedings. 



It will tljiis be seen wliat very formidiible foes tliese iusignifl cant-looking 

 little pests are to our oi'charcls, and two questions naturally arise — first, what 

 is the cause of their being so 1 and, second, where can a thoroughly radical 

 remedy be found against their ravages 1 



There are some particular kinds of apple trees more attractive to these 

 insects than others. Whether this may be attributed to the particular colour 

 of the bark, a deficiency of lime, the presence or absence of certain juices in 

 the sap, or to over-cultivation or climatic influences creating an abnormal 

 condition of the tree, and consequently rendering it more susceptible to para- 

 sitical disease, it is hard to say ; but the blight now treated of is evidently 

 more destructive in semi-tropical climates, such as Australia and New Zealand, 

 than in Britain, owing in a gi-eat measure to the effect which the frequent 

 hot sunny days succeeded by the cold frosty nights of early spring have upon 

 the circulation of the juices of the tree, unduly stimulating their flow in the 

 day time and abruptly checking their current at night, by which they burst 

 their vessels and become the food of such insects as have been already des- 

 cribed, the insects being often mistaken for the cause of the disease, while they 

 are really the effect of it. 



That the action of the American Blight, the Scale Blight, and the Cicadse 

 on our apple trees is to a great extent the effect of the last described condi- 

 tion, there cannot be much doubt. 



Assuming, therefore, such an hypothesis to be correct, it is clear that, in 

 place of the various nostrums or specifics— such as the preparations of carbolic 

 acid, corrosive sublimate, kerosene, lime, or sulphur, which are recommended 

 for washing the diseased trees, or the plastering of the infested parts with 

 moistened clay, all of which are very transient in their effects — a non-liable 

 stock to disease should be selected on which to graft any liable species the 

 grower may desire to cultivate. That there are such stocks proof against 

 blight, there are several authorities for stating, and, moreover, there is a 

 member of this Association, Mr. Lightband, senior, living in our midst, who 

 has succsssfully treated the disease by grafting an anti-blight tree, using a 

 species of winter apple, on diseased ones. 



In Darwin's book, " Animals and Plants iinder Domestication," Yol. II., 

 chapter xxi., " On Natural Selection," he says : — 



" From some unknown cause the "Winter Majetin apple enjoys the gi'eat 

 advantage of not being infested by the coccus. 



" On the other hand, a particular case has been recorded in which aphides 

 confined themselves to the Winter Nelis pear, and touched no other kind in 

 an extensive orchard. * * Liability to the attacks of parasites is also con- 

 nected with colour." 



Considerable controversy has lately been carried on in the pages of the 



