Control of San Jose Scale With Lubricating Oil. 5 



COMPARATIVE SUSCEPTIBILITY OF APPLE VARIETIES. 



The varieties of apples that have been most severely injured by 

 the San Jose scale in Arkansas are Grimes, Ben Davis, Gano, 

 Western Beauty, and Oliver. Some of the moderately susceptible 

 varieties are Early Harvest, Manmioth Black Twig, Ingram, Jona- 

 than, and Maiden Blush. Winesap, Arkansas Black, and Givens are 

 rather resistant to scale attack. 



Ben Davis is the leading commercial variety of the region. When 

 large limbs of this variety are killed by the scale it is almost cer- 

 tain that blister canker will enter where the large pruning cuts 

 have been made. For this reason Ben Davis trees, even wdien only 

 partly killed by the scale, have small chance of surviving. Figure 

 2 shows a block of Ben Davis trees in Avhich most of the scale- 



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Fig. 



-Ben Davis trees severely injured by the San Jose scale. 



killed limbs have been pruned out. It is questionable Avhether 

 many trees in this block can be saved, even after the scale has 

 been controlled. 



Vigorous-growing varieties like Mammoth Black Twig or Jona- 

 than can be brought back after a severe pruning of limbs killed 

 by the scale. Jonathan, which is probably the second variety in 

 commercial importance in this region, is far more resistant to scale 

 injury than Ben Davis or Gano. Nevertheless, it is not rare to 

 find Jonathan trees incrusted with the scale. 



CONTROL METHODS PRIOR TO 1922. 



Before the San Jose scale became destructively abundant in north- 

 western Arkansas, the usual control procedure consisted of. a single 

 spring dormant spray applied as late as possible before the buds 



