24 



BULLETIN 395, U. S. DEPARTMENT OF AGRICULTUEE. 



to peach fruits of the organisms concerned is reported in some detail, 

 as follows: 



Sources of inoculation.— The sources of inoculation were 11-day-old Lima-bean agar 

 cultures of single-spore strains of Cladosporium carpophilum, undetermined fungus A, 

 undetermined fungus B, and Dematium sp., all of which had been isolated from peach 

 twigs. Sporiferous suspensions were obtained by introducing a few cubic centimeters 

 of sterile distilled water into each culture tube, scraping the surface of the fimgal 

 growth lightly with a sterile platinum needle, and shaking. 



Germination tests were made on sterile glass slides in moist chambers with drops 

 of the sporiferous suspensions used for the inoculations. The results are shown in 

 Table IV. 



Table IV. — Summary of a germination test of the spores used in a typical fruit-inocula- 

 tion experiment, Cornelia, Ga., 1913. 



Organism. 



Cladosporium carpophilum 

 Undetermined fungus A. .. 

 Undetermined fungus B .. . 

 Dematium sp. (budding) . . 



Estimated germi- 

 nation in 3 days 

 (per cent). 



Sterile 

 distilled 

 water. 



Prune 

 decoc- 

 tion. 



Methods. — On June 6, fruits bagged on May 8 were inoculated, the technique above 

 described being followed in every respect except that in one-half of the series 0.09 per 

 cent prune decoction was substituted for distilled water in the sporiferous suspensions 

 and in the moisture apparatus. The moisture devices were refilled with sterile dis- 

 tilled water on June 11, June 20, July 17, and July 23. 



Results. — The detailed results of these inoculations are summarized in Table V. 



On the 16 control areas, Nos. 421 to 424 and 437 to 440, not a single infection occurred. 

 The results of Nos. 425 to 427, inoculated with Cladosporium carpophilum, are par- 

 ticularly striking and confirm beyond question those of preceding parallel experi- 

 ments. On the six inociilated areas 406 infections developed, while on the uninocu- 

 lated areas of the three fruits only one infection occurred. The results from the six 

 similar inoculations, Nos. 441 to 443, in which prune decoction was substituted for dis- 

 tilled water, furnish still fiu-ther confirmation of those of the preceding experiments, 

 127 infections occumng upon the areas inoculated. Only in the case of No. 441 did 

 any infection appear upon uninoculated sm'faces of these fruits, 12 lesions developing 

 within a few millimeters of the peduncle. This case stands alone among the fruits 

 bagged on May 8 and apparently represents an unusual instance of early infection 

 about the peduncle prior to bagging. This infection, however, should not be allowed 

 to lessen confidence in the results of the inoculation. That the infections upon the 

 inoculated areas resulted from the inoculation and not from natural infection is con- 

 clusive, because (1) on 100 control areas in this and the three other series of similar 

 experiments not one infection occurred; (2) the disease appeared upon the inocvilated 

 areas at the same time that it became evident upon each of the other similarly inocu- 

 lated areas of this series; (3) the lesions about the peduncle were separated from those 

 upon the areas of inoculation by a zone of clean siuface three-fourths of an inch wide; 

 and(4)in no case has natural infection been observed to occur abundantly about the stem 

 cavity, over the equatorial wettable surface, and over the equatorial protected sm-face 



