PEACH SCAB AND ITS CONTROL. 61 



Furthermore, since even on the worst affected varieties the disease 

 may be efficiently and economically controlled by spraying, the use 

 of varieties which are in some degree disease escaping or resistant 

 is imnecessary, though advisable when other factors are equal. 



SUMMARY. 



Peach scab (Cladosporium carpopMlum Thtim.) manifests itself in 

 serious spotting and cracking of the fruit and superficial injuries on 

 twigs and leaves. 



In the United States the disease has been reported from 34 States, 

 which include practically every important peach-producing district 

 east of-the Kocky Mountains. Its occurrence has also been recorded 

 in Austria, Canada, Holland, Australia, southern Europe, and South 

 Africa. 



Among the fungous diseases of the peach in the United States east 

 of the Rocky Mountains, scab ranks next to brown-rot in economic 

 importance. In many sections, before satisfactory control measures 

 were developed it rendered unprofitable the growing of certain valu- 

 able commercial varieties. Unless controlled, it would be a serious 

 menace to successful commercial peach culture in many of the most 

 important peach-producing districts of the Southern, Eastern, and 

 Central States. 



The peach-scab fungus was first described by Von Thiimen (1877), 

 who assigned it the binomial Cladosporium carpophiluTn. Oudemans 

 (1901) described as Fusicladium carpopMlum Oud. a fungus growing 

 on fallen young peaches. He lists as a synonym Cladosporium carpo- 

 pMlum Thiim., but neither gives Von Thiimen credit for the specific 

 name nor states his reasons for transferring the fungus to the genus 

 Fusicladium. Aderhold (1901) expressed the belief that 0. carpo- 

 pMlum Thiim. and C. cerasi (Rbh.) Aderh. are identical, but he 

 admittedly failed to adduce sufficient evidence to justify this con- 

 clusion. Until further evidence is presented, the writer accepts the 

 name Cladosporium carpopTiilum Thiim. for the peach-scab parasite. 



The primarily important diagnostic characters of the fungus are 

 the short, erect, more or less flexuous, one to several septate, rarely 

 branched, olivaceous conidiophores and the ovate-fusiform, obtuse to 

 apicaUy subacute, continuous or 1-septate, light fuscous conidia, 

 which are borne acrogenously, singly or in simple or branched chains. 



The fungus was isolated from peach fruit, twigs, and leaves, respec- 

 tively, in single-spore strains, which were grown comparatively upon 

 more than 30 media. The cultural differences between strains from 

 different organs of the host were no greater than those observed in 

 strains from the same organ. The fungus grew well upon this wide 

 range of media and showed only minor variations upon the different 

 substrata. 



