PEAR DISEASES 



345 



PACIFIC COAST RUST 



Caused by Gymnosporangium Libocedri (P. Henn.) Kern = G. Bias- 

 daleanum (Diet, and Holw.) Kern 



This is one of the recently recognized rusts of the pear family. 

 The name Pacific Coast rust is used in contradistinction to 

 eastern rust of pear (see page 341). The disease here consid- 

 ered was discovered in Oregon on cultivated pear several 

 years ago, but was first given special attention in 1907. Since 

 that date it has been found annually in Oregon and was par- 

 ticularly abundant in 1913. It is believed on good authority 

 that this rust will in time become one of the most important 

 pear troubles within its present range. It is most common on 

 the native hosts, Oregon crab and its apple-hybrids, the haw- 

 thorn and service-berry. It also occurs on the ornamentals 

 mountain-ash, Japanese 

 quince, Japanese pear 

 and flowering crab. It 

 is common on the cul- 

 tivated quince, but is 

 rare on the cultivated 

 apple. 



Symptoms. 



The foliage (Fig. 95), 

 fruit (Fig. 96) and stems 

 are affected, and in each 

 case there results some 

 distortion. Yellow or 

 orange spots develop 

 on the affected parts; 

 within the discolored 



FIG. 95. Pacific Coast rust on pear-leaves. 



bodies with white 



area cup-like 



margins are visible to the unaided eye. The fungus affects 

 the incense cedar (Libocedrus decurrens), symptoms show- 

 ing as brownish pustules -on the leaves .(Fig. 97). Some- 



