444 DISEASES OF ECONOMIC PLANTS 



yellowed. Cankers may almost or quite girdle the stem, 

 the diseased area becoming dark. Prune as for blight of 

 pear. 



OAK 



Leaf curl, taphrinose (Taphrina ccerulescens (Desm. & M.) 

 Tul.). — Though close kin to the peach curl, only a small 

 proportion of each leaf in spots 1-2 cm. in diameter is in- 

 volved. Defoliation may result in extreme cases, and con- 

 tinued disease each year may cause death. Affected leaves 

 should be burned and the tree sprayed as for peach curl if 

 the tree value warrants it. 



Powdery mildews, microsphgerose (Microsphcera) . — These 

 appear late and do little harm except upon nursery stock. 



Flowers of sulphur or Bordeaux mixture are useful. 



OSAGE ORANGE 



Rust (Physopella Fici (Cast.) Arthur). — The sori which 

 are scattered thickly over large areas of the lower side of 

 the leaf are small, 0.1-0.3 mm. in diameter and are pale 

 cinnamon-brown. This is known from South Carolina to 

 Texas. 



PECAN 



Scab, fusicladiose {Fusidadium effusum Wint.). — Twigs, 

 leaves, and nuts are affected in the Southern States,* 

 particularly Florida, Louisiana, Georgia, Oklahoma, and 

 Texas. Upon leaves and petioles dead spots, distortion, 

 and defoliation are caused. The new growth of twig is 

 often killed, but the greatest injury is to the nuts. 



1 Orton, W. A., Sci. n. s. 21, 503, March 31, 1905. 



