54 A Bacterial Spot of Citrus 



appearing occasionally for the past three years, has gradually increased 

 and is now assuming some economic importance. This disease has 

 been named "Black Pit of Lemon" a term which aptly describes its 

 effects on the fruit, where it causes circular-oval discoloured spots 

 5 to 20 mm. in diameter, the tissue being depressed somewhat below 

 the bottom of the normal oil glands into the white portion of the rind. 

 The cause of the disease proved to be an actively motile rod with 

 a single polar flagellum. and it has been named Baclerium cifri^niteale. 

 The description and illustrations of fruit attacked by this organism 

 correspond very closely with those of spotted lemons from the Western 

 Province, and it was surmised that the same organism would prove 

 to be the source of the trouble. A thorough investigation however 

 has shown that the organism causing the disease in South Africa is 

 quite distinct both in morphology and in cultural characters. 



Distribution. 



The Botanical Division of the Agricultural Department has no officer 

 stationed within easy reach of the citrus orchards of the Western Pro- 

 vince; arrangements were therefore made with the co-operation of 

 Mr C. W. Mally, the Cape Entomologist, to systematically inspect 

 the citrus trees in the districts with a winter rainfall, but unfortunately 

 the exceptionally rainy season prevented this plan from being carried 

 out with any degree of thoroughness. A number of orchards however, 

 have been inspected and a large number of specimens of suspected 

 fruit sent to Pretoria for examination ; and a certain amount of infor- 

 mation has been gleaned as a result of circularising the principal citrus 

 growers of the Union. 



The disease is now definitely known to occur on a number of farms 

 in the region of Simondium and Lower Paarl. It extends along the 

 Berg River Valley and has been found occurring at Welhngton, Sir 

 Lowry Pass and French Hoek. It has also been reported as occurring 

 at Stellenbosch, but no specimens of supposedly infected fruit from 

 that locality have been examined. 



So far as can be ascertained the Transvaal is entirely free from the 

 trouble; there is certainly no sign of it at Warmbaths or Nelspruit, 

 and growers at Barberton state that during a careful examination of 

 their trees they failed to find anything at all resembling the bacterial 

 spot. The Rustenburg area also seems to be clean; one box of 

 oranges and lemons sent from there in response to enquiries proved 



