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MANUAL OF FRUIT DISEASES 



The disease may first be observed on the white pine (Fig. 57) 

 in the spring from April to early June. The stem or branches 

 are often girdled and the portion above dies. Most young 

 trees die in a relatively short time ; others live for some time, 

 but even old stems finally succumb, the tree eventually break- 

 ing at the lesion. The disease in its early stages shows peculiar 



FIG. 55. European currant-rust ; uredinia on lower surface of black 

 currant leaf. 



fusiform, or spindle-shaped, swellings which taper upward. 

 These are usually found on wood at least three years old. When 

 a swelling is first noticeable, small transparent spots appear 

 which develop into blister-like pustules surrounded at the base 

 by a translucent spot, whence the name blister-rust. These 

 pustules break open and drops of sweet, honey-colored fluid 

 exude. Later, spore-pustules break through the bark. These 

 are small, scattered, and from them orange-colored masses of 

 spores push forth through the break in the bark (Fig. 57). 



