DISEASES OF SPECIAL CROPS 



107 



This disease of pears is particularly abundant upon sev- 

 eral varieties of the Japanese strain. 



Bitter rot, ripe rot (Glomerella rufomaculans (Berk.) 

 Spaul. & von Schrenk). — This disease is of much less 

 frequent occurrence upon the pear than upon the apple. 

 For description and treatment, see pp. 64 and 74. 



Fig. 4-4. — Scab on California pears bought in Raleigh. Original. 



Powdery mildews, sphaerothocose and podosphaerose. 

 — See apple. 



Scab (Venturia pyrina Aderh.). — This scab much 

 resembles that of the apple and consists of a surface blotch 

 or scab, often accompanied by a peculiar cracked appearance 

 of the skin. This symptom, however, is a secondary effect 

 which is not necessarily present. Upon the twigs rough 

 cankers are formed. 



Smith ^ of California recommends plowing under or 

 clearing away dead leaves and using a dormant spray fol- 

 lowed by two applications of Bordeaux mixture while 



1 Smith, R. E., Cal. Agr. Exp. Sta. Bui. 163, p. 17, 1905. 



