Ethel M. Doidgk 429 



of the tomato, Aplanobacter michiganense Erw. Sra. (2) and an organism 

 believed to be identical with Bacillus Lathyri Manns and Taubenhaus(i). 



Aplanobacter michiganense is non-motile, tolerates considerable alkali, 

 growing in — 25 and — 30 peptone bouillon and does not grow in peptone 

 beef bouillon acidified to + 20, + 25, or -f- 30 with malic or citric acid. 



The second organism has four to six peritrichous flagella and grows 

 in Uschinsky's solution : cultures in nitrate broth give a strong reaction 

 for nitrite on the second day. 



The three organisms appear to be quite distinct, and Bacterium 

 vesicatorium differs considerably from the other two in its effect on the 

 host. 



Control of the Disease. 



The organism is not very sensitive to the fungicides usually employed 

 in spraying solutions, and experience has shown that spraying is of 

 little use in combating plant diseases caused by bacteria. This is par- 

 ticularly the case with organisms disseminated, chiefly by rain splash 

 and infecting the plant through the stomata. 



It appears to be the custom of the market gardeners in the Pretoria 

 district to save seed from their own plants for the following season. 

 This custom is probably in part responsible for carrying over the disease 

 from one season to another. Certain varieties are more susceptible than 

 others, but it has been found practically impossible to discover the name 

 of the varieties usually grown. The following methods are therefore 

 suggested for the control of the disease. 



(1) Selection of resistant varieties. 



(2) Sterilisation of the seed by means of formalin or mercuric 

 chloride. 



(3) A long crop rotation. 



(4) Destruction of diseased fruit and of affected plants at the end 

 of the season. 



In connection with (3) it will also be of importance that the irrigation 

 furrows shall not be allowed to flow through the old tomato bed to the 

 site selected for tomatoes in the following season. 



REFERENCES. 



(1) Paine, Sydney G. and Bewley, W. F. Studies in Bacteriosis, IV — "Stripe" 



disease of Tomato. Annals of Applied Biology, vr. 183-202. Dec. 1919. 



(2) Smith, Erwin F. The Grand Rapids Tomato Disease. Bacteria in Relation to 



Plant Diseases, in. 161. 1914. 



