WATERMELON STEM-END ROT 



[preliminary paper] 



By F. C. Meier, 



Sftident Assistant, Cotton and Truck Disease Investigations, 



Bureau of Plant Industry 



During the last few years in certain parts of the United States shippers 

 have been seriously troubled by a decay which attacks watermelons 

 {Citrullus vulgaris) in transit and may sometimes destroy or render 

 unsalable a large percentage of a shipment before it reaches its destina- 

 tion. Owing to this fact, in the season of 1915 the Department of 

 Agriculture began a careful investigation of shipping conditions, in the 

 course of which the present writer had an opportunity to make a labora- 

 tory study of some decayed material. 



This material was taken from a shipment received in Washington, 

 D. C, on July 24, 1915. The shipment consisted of five carloads of 

 approximately 900 watermelons each, no one car of which yielded more 

 than 300 salable melons, owing to the prevalence among them of the 

 disease. The decayed watermelons were distributed through the car 

 entirely without reference to position, a fact which made it seem mani- 

 festly impossible that the trouble could have originated from mechanical 

 or chemical injury received from contact with the walls or the floor of 

 the car. 



This examination indicated, moreover, that, as has been reported in 

 the case of other shipments, the injury of these watermelons had occurred 

 in a very uniform manner. In its early stages the presence of the decay 

 was indicated by a watery discoloration of the rind in an area closely sur- 

 rounding and apparently extending from the stem. Beginning in this 

 way there were all stages of decay up to those where about half or three- 

 quarters of the melon were involved. In such cases the rind of this por- 

 tion had become soft and wrinkled, so that in cross section it appeared 

 much like that of the watermelons shown in the lower row of Plate XVII, 

 figure I . The meat below this part of the rind was slimy and blackened, 

 while that at the opposite end of the melon remained sound, not having 

 as yet become included in the decay. Owing to the warm, moist con- 

 ditions at this season, the portion involved was covered by a gray or some- 

 what black mold, so that the origin of the trouble could not be readily 

 ascertained. 



An abundance of material being available at this time, an attempt 

 was made to find out whether the injury was due to the action of some 

 fungus, and, if this proved to be the case, to obtain the specific organism 



Journal of Agricultural Research, Vol. VI, No. 4 



Dept. of Agriculture, Washington, D. C. Apr. 24, 1916 



dg G— 76 



(149) 



