264 



FUNGOUS DISEASES OF PLANTS 



XLIV. APPLE SCAB AND PEAR SCAB 

 Venturia Pomi (Fr.) Wint. and Venturia Pyrina Aderh. 



ADERHOLD, RUD. Die Fusicladien unserer Obstbaume. Landwsch. Jahrb. 



25: 875-914. pis. 29-31. 1896; Ibid. 29: 541-587. ph. 9-12. 1900. 

 BEACH, S. A. Experiments in Preventing Pear Scab in 1893. N. Y. Agl. 



Exp. Sta. Built. 67 : 183-204. 

 CLINTON, G. P. Apple Scab. 111. Agl. Exp. Sta. Built. 67 : 109-156. 1901. 



(Good bibliography.) 

 DUGGAR, B. M. Some Important Pear Diseases. Cornell Agl. Exp. Sta. 



Built. 145: 616-622. figs. 168-170. 1898. 

 LAWRENCE, W. H. The Apple Scab in Western Washington. Washington 



Agl. Exp. Sta. Built. 64: 1-24. pis. 1,2. 1904. 

 SMITH, RALPH E. Pear Scab. Calif. Agl. Exp. Sta. Built. 163: 1-18. figs. 



Two important fungous diseases popularly known as apple and 

 pear scab have received at the hands of both mycologists and 



horticulturists considerable 

 attention within the past 

 thirty years. The fungi 

 causing these diseases are 

 very closely related, al- 

 though quite generally re- 

 ferred to two distinct 

 species. The conidial form 

 of each of these fungi was 

 first found parasitic upon 

 its respective host ; hence 

 these fungi have long been 

 known by the names of 

 these conidial forms, Fusi- 

 cladiuDi dcndriticuni and 

 7v/ s ic la din m Py r i n u HI . 

 More recently an ascomy- 



cetous fungus, Venturia Pomi, has been found to constitute the 

 perfect stage of the apple scab organism, and a related perithecial 

 form, Venturia /[yrina, has been connected with the pear scab 

 fungus. The perithecial stages develop saprophytically, a phe- 

 nomenon characteristic of many Ascomycetes. 



Distribution and climatic relations. In the United States both 

 the scab of the apple and of the pear are widely distributed. 



FIG. 116. A SEVERE ATTACK OF PEAR SCAB 

 ON FLEMISH BEAUTY 



