INOCULATION KXPERIMENTS WITH SPECIES OF COC- 

 COMYCES FROM STONE FRUITS^ 



By G. W. KeiTT 

 Associate Professor of Plant Pathology, University of Wisconsin 



INTRODUCTION 



For three years the writer ^ has had under investigation leaf spot dis- 

 eases of cherries and plums (Prunus spp.) in Wisconsin. In connection 

 with this work in 191 6 and 191 7, more than 1,000 cross-inoculation 

 experiments were conducted with Coccomyces spp. from a number of the 

 more common wild and cultivated species of Prunus of the State, with 

 the aim of furthering our understanding of the relationships of these 

 pathogenes to their hosts and to one another. This paper is a report 

 of progress on these experiments. It is presented at this juncture be- 

 cause of the temporary discontinuance of the work owing to the stress 

 of war conditions. Final conclusions and the discussion of results in 

 relation to the work of others and in their bearing upon other phases 

 of the leafspot problem are reserved for a future paper. 



EXPERIMENTS OF 1916 



Preliminary experiments in 191 5 and in the spring of 191 6, conducted 

 in the light of the results of the similar work of Higgins,^ formed a basis 

 of experience upon which to develop methods for further work. These 

 tests showed that satisfactory experiments might be conducted either 

 in the greenhouse or out of doors, and that, particularly in the out- 

 door inoculations, it is essential to have means of maintaining high 

 humidities about the experimental plants or organs without the de- 

 velopment of excessively high temperatures. In order that the con- 

 ditions of the experiments might be as nearly normal as possible, the 

 further inoculations of 191 6 were made out of doors. The following 

 method was employed, especial attention being given to standardiza- 

 ation of technic, with the aim of increasing both the comparative value 

 and the facility of presentation of results. 



' Approved for publication by the Director of the Wisconsin Agricultural Experiment Station. 



2 KEITT, G. W. a PRELIMrNARY REPORT ON INVESTIGATIONS OP LEAFSPOT OP CHERRIES AND PLUMS IN 



WisconAi. (Abstract.) In Phytopathology, v. 6, no. i, p. 112. 1916. 



SECOND PROGRESS REPORT ON INVESTIGATIONS OP LEAFSPOT OP CHERRIES AND PLUMS IN WIS- 

 CONSIN (Abstract.) /« Phytopathology, v. 7, no. i, p. 75-76. 1917. 



THIRD PROGRESS REPORT ON INVESTIGATIONS OF LEAFSPOT OP CHERRIES AND PLUMS IN WIS- 

 CONSIN (Abstract.) In Phytopathology, v. 8, no. 2, p. 72-73. 191S. 



3 HiGGINS, B. B. CONTRIBUTION TO THE LIFE HISTORY AND PHYSIOLOGY OP CYLINDROSPORtUM ON STONE 



FRUITS. In Amer. Jour. Bot., v. i, no. 4, p. 145-173, pi. 13-16. 1914. 



Journal of Agricultural Research, Vol. XIII, No. 11 



Washington, D. C. June 10, 1918 



np Key No. Wis.-i2 



(539) 



56113°— 18 2 



