176 FUNGOUS DISEASES OF PLANTS 



II. PEACH LEAF CURL 

 Exoascus deformans (Berk.) Fuckel 



DUGGAR, B. M. Peach Leaf Curl. Cornell Agl. Exp. Sta. Built. 164: 371- 



388. figs. 66-72. 1899. 

 PIERCE, N. B. Peach Leaf Curl : Its Nature and Treatment. Div. Veg. Path. . 



and Phys., U. S. Dept Agl. Built. 20: 1-204. pis. 1-30. 1900. 

 SELBV, A. D. Preliminary Report upon Diseases of the Peach. Ohio Agl. 



Exp. Sta. Built. 92 : 226-231. 1898. 

 SELBY, A. D. Variation in the Amount of Leaf Curl of the Peach (Exoascus 



deformans) in the Light of Weather Conditions. Proc. Assoc. Prom. 



Agl. Sci., Ann. Meeting 20: 98-104. 1899. 



Peach leaf curl (Krauselkrankhcit in Germany ; Cloqiie du 

 pecker in France) is an important fungous disease affecting par- 

 ticularly the leaves and tender shoots of the peach, but injuring 

 likewise, occasionally, the flowers and fruit. 



Distribution. Attempts to determine the country which might 

 be regarded as the original home of this fungus have proved 

 wholly futile. Leaf curl is now a more or less common disease 

 in nearly all peach-growing regions of the world. In North 

 America it is known throughout the country, at least east and 

 west, and from northern Canada to the Gulf of Mexico ; while 

 in South America it has also been reported from several peach- 

 growing districts. In Europe it has long been common, having 

 been reported in England as early as 1821, and it is disastrous 

 in many sections of China and Japan. This disease occurs also 

 in southern Africa, and from the Sahara northward in Algeria. 

 According to reports it prevailed in Australia even in 1856, and 

 it has proved most pernicious to peach-growing interests in New 

 Zealand. In general, therefore, this disease is known wherever 

 peach growing is practiced. In the United States the general 

 regions in which the more serious' and constant injuries have 

 been felt are apparently two, viz., the region of the Great Lakes 

 and the Pacific Slope region, the latter including also districts in 

 central and northern California. 



Climatic relations. Plant pathologists are almost unanimous in 

 the assertion that this fungous disease is most prevalent and most 

 disastrous when the spring is cold and damp. Practical orchardists 

 likewise concur in this opinion. Pierce about ten years ago col- 

 lected statistics from about one hundred orchardists bearing upon 



