ON THE OCCURRENCE OF BACTERIUM CAMP EST RE 

 (PAM.) SM., IN SOUTH AFRICA. 



By Ethel M. Doidce, D.Sc. F.L.S. 



(Plates 8-11 and three text fijjures.j 



In volume 2 of his work on " Bacteria in Rehition to Plane 

 Diseases," Dr. Erwin F. Smith states that nothing is known of 

 the occurrence of Bacterium canipcstre outside of Europe and 

 America, except that Kirk has recently reported it from New 

 Zealand. It has been known for some years that a disease 

 similar to that caused by this organism has been found attack- 

 ing cruciferous plants in this country, but only recently has a 

 favourable opportunity occurred for studying it in detail and 

 establishing the identity of the causal organism. Investigation 

 has shown that the trouble is extremely common and very wide- 

 spread, and I think largely responsible for the failure of cab- 

 bages orown during the summer months. 



Geographical Dtstributton. 



The first record which we have of the disease is of a num- 

 ber of cabbage-leaves sent for examination from Barberton in 

 1906, and a little later from Mooi River, in Natal. In both 

 cases the specimens were characterised by the blackened vessels 

 of the fibro-vascular bundles, and yellowing of tlie affected 

 ])arts. Bacteria were present in large numbers in the bundles. 



In 191 2, a farmer at Piet Retief reported the disease in 

 two fields of cabbages and caulitlowers 150 yards apart; he 

 complained that the leaves withered and turned yellow, ai-id that 

 some of the heads were quite rotten inside. Some time before 

 writing, in looking through his crop and selecting cabbages for 

 the market, a large cabbage fell to pieces as he was examining 

 it to see whether it was hard enough to cut ; later this plant 

 developed a number of small heads, one of which he sent for 

 examination. This specimen also showed the characteristic 

 blackening of the veins and yellowing of the leaf tissues. The 

 same symptoms were observed in some cauliflower leaves sent 

 from the same locality, and in both cases there were innumer- 

 able bacteria in the fibro-vascular bundles 



It was an outbreak of the disease in the writer's private 

 garden during the winter of 1914. which afforded a favourable 

 opportunity for studying the disease in the laboratory. A num- 

 ber of cabbage plants were attacked which had been obtained 

 as seedlings from a local seedsman — a fact which will be re- 

 ferred to later in discussing the origin of infection — and this 

 led to the discovery that the disease is very widespread and 

 extremely common, and that in the neighbourhood of Pretoria 

 anywav it would be difficult to find a garden entirely free from 



