THE MONTHLY BULLETIN. 



51 



There is considerable difference in the' attacks upon varieties of the 

 apple. The Northern Spy is practically immune and for this reason 

 is much sought after as a resistant root stock for grafting purposes. 

 Vigorous growing varieties such as the Rhode Island Greening and 

 Bellflower are very much injured. In Humboldt County the former 

 is decidedly undesirable because of the great injury from woolly aphis. 



Fig. 4 0. — The 

 woolly aphis, Erio- 

 soma I an i g era 

 (Hausm.) on twig of 

 apple. (After Hall.) 



Fig. 41. — The work of the 

 woolly aphis xipon the roots of an 

 apple nursery tree. (Original.) 



Practically all other commercial varieties are affected in a more or 

 less degree, the King of Tompkins County being injured the least in 

 the north. 



Control. — The control of the pest is given quite fully on pages 46 

 and 47. The important factors to be taken into consideration are 

 to procure a spray that will dissolve the cottony covering; to maintain 

 a pressure from 150 to 200 pounds; to apply a coarse driving spray 

 and to do the work thoroughly, making as many repeated applications 

 as necessary. 



