November 3, 1911] 



SCIENCE 



615 



named after Mr. Horace G. Smith, of Denver, 

 who has long studied the fauna of Colorado, 

 and who went to great trouble to revisit the 

 locality and obtain additional material. The 

 other Cyprinids found by Mr. Smith at Jules- 

 burg were Sernotilus atromaculatus macro- 

 cephalus (Girard) and Phenacobius scopifer 

 (Cope). 



t. d. a. cockerell 

 Universitt of Colorado 



a bacterial gummosis of cherries 



Certain varieties of the cultivated sweet 

 cherries grown in the Pacific northwest are 

 very subject to a diseased condition which is 

 commonly known as " cherry gummosis." 

 The disease is characterized by more or less 

 copious exudation of gum from the trunk, 

 branches, spurs and buds as well as by a 

 pustulated appearance of the bark near the 

 diseased areas. Often but little gum is ex- 

 uded, but in such eases an examination of the 

 affected trees generally discloses discolored 

 tissues which is infiltrated with gum. Such 

 areas are spongy to the touch and are usually 

 discernible by the variation in color of the 

 bark as compared with that of the normal. 



Gummosis is found in every cherry grow- 

 ing section of Oregon, but it is in the more 

 humid portion of western Oregon that its 

 prevalence and destructiveness gives it the 

 rank of a major disease, and where its appear- 

 ance in an orchard is most dreaded by the 

 grower. 



Cherry gummosis appeared soon after the 

 first planting of cherries in the state. Its 

 prevalence has varied from season to season, 

 being apparently more abundant in those 

 years when the trees experienced rather sud- 

 den extreme variations in temperature after 

 growth had started. This has led observing 

 growers to attribute the trouble chiefly to the 

 climatic factor. The disease appears on a 

 wide range of soil, but the trees growing in 

 the more exposed locations or on poorly 

 drained or shallow soil are generally the worst 

 affected. 



Cherry gummosis appears in both a local- 

 ized and generalized form. In the former, the 



disease is apparently confined to rather lim- 

 ited areas on the trunk or branches, such 

 areas being most often associated with a 

 blighted spur or bud. In the generalized 

 form, large areas of the trunk or branch may 

 become involved, and it often results in com- 

 plete girdling. This latter type of gummosis 

 often appears to originate in the crotch of the 

 tree. 



The writer was assigned the problem of in- 

 vestigating the possible causes and preven- 

 tion of cherry gummosis while a student in 

 the Oregon Agricultural College. In the 

 spring of 1909, I noted bacteria in sections of 

 blighted cherry fruit spurs, and upon making 

 cultures from fresh material, found the or- 

 ganisms to be rather constantly associated 

 with such diseased spurs. I had to drop the 

 investigation for the time being on account 

 of the stress of other work, but from the few 

 direct inoculations made into healthy spurs 

 a blighting or gumming occurred. 



In the spring of 1910 a large number of 

 cultures were made from material procured 

 in different cherry-growing sections. In the 

 agar plates resulting from such cultures, one 

 type of organism seemed to predominate, and 

 it often appeared in pure culture. From 

 pure cultures thus obtained a series of inocu- 

 lation experiments were made in which the 

 organisms were transferred from agar slants 

 to healthy fruit spurs by needle pricks. The 

 spurs thus inoculated, blighted or gummed, 

 while the checks healed without blighting or 

 gumming. The typical organism was re-iso- 

 lated from the inoculated spurs and again 

 inoculated into other healthy fruit spurs. 

 These inoculated spurs again blighted and 

 gummed while the checks remained normal. 



During the present season the work has 

 been continued, and several series of inocu- 

 lations have been made with different strains 

 of the organism. As a result of these inocu- 

 lations and reinoculations in which I hare 

 tried to follow implicitly the Rules of Proof 

 of Pathogenicity as found in Smith's " Bac- 

 teria in Relation to Plant Diseases," I believe 

 I have found a specific cause of at least one 

 form of cherry gummosis. 



