490 CITRUS FRUITS AND THEIR CULTURE. 



die-back, some have argued that this disease is due to a 

 fungus. This is not the case, however, and the beneficial 

 results must be attributed to the chemo-toxic effects of 

 the solution in accelerating the assimilative processes in 

 the leaves and other green parts of the trees. 



If the spraying method of control is adopted, three 

 or four applications should be given at intervals of about 

 thirty days. It must be borne in mind that Bordeaux 

 mixture is not an insecticide, but on the other hand its 

 use is generally followed by an enormous increase in the 

 number of scale insects. Therefore, it is absolutely neces- 

 sary to follow the applications of Bordeaux up with a good 

 insecticide, such as Good Potash Whale-oil Soap, No. 3, 

 to keep the scale insects in check. If the grower is unwill- 

 ing to do this then spraying must be left alone and the cul- 

 tural treatment adopted. 



Blight. This is the most dreaded of all citrus diseases, 

 because, thus far, no satisfactory means have been discov- 

 ered of preventing or combating it. The history of the 

 disease is not definitely known, but it has been prevalent 

 in the Florida districts for a number of years. Many of 

 the worst affected groves have disappeared, but the dis- 

 ease is still quite prevalent. 



Blighted trees appear as though suffering from 

 drought, or look as though they had recently been trans- 

 planted. The leaves wilt, droop and finally drop off. In 

 some cases the disease works very rapidly, in others its 

 progress is decidedly slow. It often manifests itself on 

 a single branch and from that gradually spreads over the 

 whole tree. Trees affected in this way live for a consid- 

 erable length of time. But in many cases it soon brings 

 about the death of the tree. Shoots spring out from the 

 trunk and crown roots of the tree. These also succumb 



