CITRUS FRUITS 121 



possible that some other supposedly distinct diseases are 

 in reality forms of gummosis. 



This disease is most common about the crown of the 

 trees, but frequently extends up the trunk and down- 

 ward along the roots. There is first an exudation of 

 gum followed by a brownish coloration and sometimes 

 an odour similar to decaying oranges. In Cuba a 

 peculiar gumming of the twigs has also been observed. 

 The most satisfactory remedies consist in careful cultiva- 

 tion, the removal of the soil from about the crown of 

 the tree so as to admit of thorough aeration, generous 

 and uniform supply of water, cutting away of the 

 diseased parts, and painting with a solution of equal 

 parts of crude carbolic acid and water, and then 

 covering the wounds with wax. The sour orange seems 

 to be the most resistant variety, and budding on sour 

 orange or other resistant stock is to be encouraged. 



Blight. This is one of the most puzzling of the 

 leaf diseases of the orange. It is very common and 

 very destructive in Florida, and has been reported from 

 Cuba. No specific organism has been discovered, and 

 we are therefore compelled to consider it a physiological 

 disease. The leaves wilt and finally fall, in some cases 

 rapidly and in others very slowly. In some cases it 

 originates in a part of the tree and gradually spreads 

 over the entire tree. It is very frequently associated 

 with other diseases, especially the anthracnose, which 

 complicates the diagnosis. 



With our present meagre knowledge of the disease 

 and its cause, the only remedy that can be suggested is 

 to pull out and burn all diseased trees. 



Mottled Leaf. This disease has given some trouble 

 in California. It appears to be a physiological trouble 

 caused by the roots penetrating an unfavourable sub- 

 soil. 



Dieback or Exanthema. This is one of the most 

 serious diseases of the citrus fruits in Florida, and has 

 given some trouble in California. It has also been 

 reported from Australia and Hawaii, and is said to 



