lOt) DISEASES OF ECONOMIC PLANTS 



ever, is undoubtedly in tlie fall, when the foliage is still on 

 the trees and the contrast between that on the blighted 

 and that on the healthy limbs is strong. It is further 

 necessary to make a weekly inspection of every tree through- 

 out the growing season, beginning when the blossoms fall, 

 and to cut out bhght whenever it is found. 



In each case it is necessary to cut well below any external 

 evidences of the disease. To avoid spreading the infec- 

 tion, in case the pruning tools should accidentally cut into 

 the diseased tissue, the cutting blade should each time be 

 disinfected by wiping it with a cloth saturated with a 

 strong solution of corrosive sublimate (1 part to 1000). 

 When the wound made by this excision is at all large, it 

 should be disinfected with the corrosive sublimate solution. 

 Particular care should be taken to remove and burn all dis- 

 eased spurs and watersprouts. 



Unless continued careful inspection is given, but little 

 benefit will follow. 



Rust (Gymnosporangium globosum Farl.). — The rust of 

 pear is very similar in nature to the rust on the apple, though 

 less often injurious. It consists of two stages, a summer 

 stage and a winter stage. The summer stage produces the 

 rust on the leaves of the pear, while the winter stage forms 

 the familiar cedar apple upon the cedar tree. 



The remedy, as in the case of the apple, consists in re- 

 moving all red cedar trees from the neighborhood of the 

 pear orchard; thus eliminating the source of infection. 

 When this is impossible, the trees should be sprayed with 

 the Bordeaux mixture immediately after the early rains 

 which cause the gelatinous horns on the cedar apple, and 

 thus furnish the supply of spores for the spring infection. 



