E. M. DOIDGE 3 



Of the six diseases mentioned above, four are due to the attacks of 

 fungi; the remaining two, of which the cause has not been determined, 

 differ essentially in their effects from the one to be described. 



Geographical distribution . 



Our attention was first drawn to this disease by Messrs Winter Bros, 

 of Barberton, who sent specimens of mangoes from their trees for 

 examination. They stated that it made its first appearance there after 

 the great hail storm in October 1906, which damaged the trees con- 

 siderably ; the marks of the hail are still visible on the trunks and larger 

 branches. A tree standing in a corner of the orchard was the first to 

 become infected, and from this point the infection rapidly spread with 

 the prevailing winds until every tree was diseased. In 1908, in spite 

 of repeated spraying with Bordeaux mixture, they obtained not a single 

 fruit from 60 trees. Almost all the fruit in the town was similarly 

 affected, but at the farms, some distance away, the fruit was then 

 perfectly sound. Every season up to the present (1913-14) the disease 

 has been steadily gaining ground, each year spreading to some orchard 

 which was previously free from infection, and this in spite of the fact 

 that there have been four very dry seasons in succession, a condition 

 which — as will be shown later— is highly unfavourable to the spread 

 of the disease. 



In 1910, a sample of infected fruit was received from Warmbaths. 

 On making an inspection of the orchard in which the fruit was grown, 

 it was found that the infection had started at a corner of the orchard 

 where some young trees had been planted." These young trees were 

 badly infected, and, as at Barberton, the infection had spread with the 

 prevailing winds until a large proportion of the trees was affected. 

 The trees which were apparently the original source of infection had 

 been purchased in Natal, and it seemed probable that in this case the 

 disease had been introduced from that province. 



The writer visited Natal in March 1910, with a view to discovering 

 whether this was the case, and found that it was prevalent throughout 

 the mango-growing districts of Natal. It was actually observed on 

 the leaves and stems of trees at Hillarys, Malvern and Durban. During 

 a later visit in December 1911, it was seen on the fruit in all these 

 localities. 



In 1910, Mr R. A. Davis, the Government Horticulturist, reported 

 that he had examined trees in Swaziland and found them quite healthy. 

 These trees had all been imported from Natal some 14 years previously, 



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