A Tomato Canker. 



721 



The Cause of the Disease. 



The cause of this disease is a yellow bacterium belonging to 

 the same group as the organisms causing citrus canker, walnut blight, 

 black rot in cabbage, etc~ It is not identical with any of these, and 

 in a number of cross inoculation experiments it failed to infect any 

 of these hosts; it only attacks the tomato and a few closely related 

 l)lants. The bacterium appears to be one hitherto uudescribed, and 

 will be described in detail elsewliere under tlu> name Jhtcfcri u m 

 rcsicfiforiuTn n. sp. 



CoNJ'UOi; OF llll'; l)lSlv\SE. 



The organism is not very sensitive to the fungicides usually 

 employed in spraying solutions, and experience has shown that spray- 

 ing is of little use in cond)ating plant diseases caused by bacteria. 

 This is particularly 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 gardeneis 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 names of the varieties usually grown. The following methods 

 are therefore suggested for the control of the disease : — 



(1) Selection of resistant varieties. 



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



chloride. 



(-')) 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 irri- 

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

 to the site selected for tomatoes in the following season. 



Fruit Export. 



The following is a return of fruit shipped o^■erseas dui'ing the 

 month of September, 1920: — 



Ux Ex East Ex Port Ex Mossel Ex 



Variety. 



Oranges ... . 

 Naartjes ... . 



Lemons 



Grape fruit 

 Pineapples 



Durban. London. Elizabeth. Bay. 

 Boxes. Boxes. Boxes. Boxes. 



1058 151 4568 81 



— 304 — 



Total ... 



1058 



151 



4872 ^1 18,654 24,816 



The total shiptnents from all ports during July aiid August, 1930, 

 were 37,438 and 29,365 boj^ps respectively. / 



