38 



Bacterial Disease of the Mango 



Only a few substances could be satisfactorily tested in this way, 

 and the results obtained with these may be tabulated as follows: 



Germicide 



Formalin 

 Copper sulphate 

 Phenol 



Sodium nitrate 

 Kainite 



Amount to 

 retard growth 



20,000 



1,500 



1,500 



25 



25 



Amount to 

 inhibit growth 



1 : 10,000 

 1 : 1,000 

 1 : 1,000 

 1: 10 

 1 : 10 



Amount to 



kill organism 



in 30 mins. 



1 : 1,000 

 1:200 

 1 : 100 



Lithium sulphate in the proportions of 1 : 25 had no effect in 

 retarding growth. I did not find any involution forms in cultures 

 containing 4 % of this salt. 



Substances which caused precipitates in nutrient broth were tested 

 in a slightly different way. Tubes were prepared containing sterile 

 distilled water with various percentages of the germicide. Into these 

 •1 cc. of a 24-hour old broth culture was pipetted and they were allowed 

 to stand at 30° C. for thirty minutes. Plates were then poured as from 

 the beef broth tubes in the previous experiment and these were kept 

 under observation for several days. 



The results obtained were as follows: 



Germicide 

 Mercuric chloride 

 Hycol 

 Formalin 

 Cyllin 

 Lysol 



Copper sulphate 

 Potassium permanganate 

 Iron sulphate 

 Iron sulphide 



Amount to kill 



large percentage 



of organisms 



in 30 mins. 



1 : 20,000 

 1 : 2000 

 1 : 2000 

 1 : 2000 



1 : 400 

 1 : 100 

 1:75 



Amount to kill 



all organisms 



in 30 mins. 



10,000 



1000 



1000 



1000 



400 



400 



350 



25 



25 



From this table it is evident that the organism is most susceptible 

 to mercuric chloride, but it was not considered advisable to make use 

 of this substance for spraying owing to its highly poisonous nature. 



The results of spraying with Hycol have been given in another part 

 of the paper. 



Action of sunlight. The organism is not sensitive to exposure to 

 light. It grows well in the diffused light of the laboratory, though not 

 so rapidly as in the dark. 



