THIRTY-FOURTH FRUIT-GROWERS^ CONVENTION, 



85 



the twigs, and the bark of the hitter breaks out in corky protuberances 

 or pustules. ^lore or less gumming is associated with the latter. This 

 disease is described in Florida as being due to an excess of organic 

 nitrogen in the soil. That this is not entirely the case, but rather that 

 its cause is more complicated than this, is shown by the appearance 

 of the trouble in this State, where it is limited almost entirely to a 

 certain type of soil. This is the coarse, granitic, ver^' porous soil, which 

 i^^ found particularly along the base of the mountains in various places 

 between Highlands and Pasadena. On such soils the Florida die-back 

 is of quite frequent occurrence. There have been a very few cases of 

 the disease on heavier soils Avhere the Florida experience seems to hold 

 true, all the instances on such soils of which we are aw^are having been 

 associated with very heavy applications of fertilizers rich in organic 

 nitrogen. In the case of the type of soil mentioned, however, the 

 disease occurs very severely in many instances where only moderate 

 amounts of fertilizers have been applied. The most pronounced quality 

 of this soil is the free passage which it affords to water. It becomes 

 very wet during irrigation, but unless water is applied very thoroughly 

 and carefully and quite frequently, the upper soil becomes absolutely 

 dry between irrigations. This soil also takes up water very poorly 

 in a lateral direction, so that the space between the trees and much 

 of the whole body of soil becomes extremely dry in many orchards. 

 The disease appears to be brought about in some ilianner through an 

 irregular food supply, resulting from the irregular water supply which 

 trees get in this soil, unless irrigation is particularly well carried out. 

 With trees which are not well fertilized, the effect is simply one of 

 ordinary die-back. True exanthema seems to result where the soil is 

 of the type described, and a fair amount of fertilizing material has 

 been applied. It is apparently a sort of indigestion in the tree, more 

 food being taken up during irrigation than the tree can take care of 

 after it gets into the condition of drynass which follows. On heavier 

 soils the same thing occurs only where very excessive amounts of 

 nitrogen have been applied. 



Cases of ordinary die-back, failure to grow, poor development, 

 mottled leaf, poor production, barrenness, etc., are of very frequent 

 occurrence, but can not be ascribed to any one cause or considered as 

 representing any special form of disease. These conditions result in 

 a great majority of cases from failure of good cultural methods or 

 unfavorable conditions in the location of the orchard. 



With the orange, the fruit itself is affected by two very characteristic 

 troubles, both apparently due to irregularities or abnormal conditions 

 in the development of the fruit, from causes which can not be fully 

 explained. We refer to the puffing and splitting of the fruit. We can 

 give no information of definite value as to the exact nature or means 

 of control of these troubles. 



In regard to the treatment or means of avoiding the various diseases 

 which have thus far been mentioned we can give no absolute rules to 

 fit all cases; but, in this connection, the following remarks by Mr. C. C. 

 Chapman, at the Citrus Convention held in Riverside in January, 1907, 

 are very suggestive : ' ' There are certain general conditions which I 

 believe are applicable to all of Southern California. First, I think it 

 is an essential requirement that you should keep your grove absolutely 



