' CITEUS DISEASES. 47 



been expended in the attempt to eradicate it, and the fight has not 

 been concluded. 



Among otlier diseases which can be mentioned in this connection 

 are the brown rot (Pythiacystis) , which caused enormous losses to 

 the California citrus industry before a means of control was devised ; 

 the cottony rot or mold, attacking the fruit as well as the twigs; 

 several types of gummosis due to fungi not known in Porto Rico; 

 and a new bacterial disease of twigs, citrus blast. In Florida there 

 is a disease known as nail-head rust or scaly bark, due to a certain 

 fungTis also as yet unknown to us. Jamaica reports a fungus gall 

 on the branches, and in Ceylon a powdery mildew is so serious that 

 it is said to be impossible to raise citrus fruits even for home con- 

 sumption. 



A considerable number of other diseases, all capable of causing 

 heavy damage, could be mentioned, but these few will suffice to bring 

 out vividly the importance of keeping at arm's length, by means of 

 quarantine, any addition to the already formidable list of Porto Rican 

 citrus diseases. Growers can cooperate most effectively in this im- 

 portant work by not attempting to import any citrus stock, and by 

 reporting anyone who does. Specimens of any unknown disease, 

 or type of injury appearing in the grove, should be sent to the Ex- 

 periment Station for determination. Quick action in cases of this 

 kind will make it possible to check a new disease in the incipient 

 stage. 



In studying the diseases of citrus in Porto Rico, it speedily be- 

 comes apparent that they are much the same as those reported for 

 Florida, differing on the other hand very widely from those of Cali- 

 fornia. That this should be the case seems reasonalile, when it is 

 remembered that the bulk of the groves of the Island originated di- 

 rectly or indirectly from budwood brought from the former State. 

 There is, as might be expected, an even greater similarity to condi- 

 tions existing in Cuba and the Isle of Pines, since the industry in 

 those islands is but an offshoot of that of Florida, and in addition 

 the soil and climate of Porto Rico and Cuba are much alike. 

 Certain diseases, black melanose for example, which are of very minor 

 importance or non-existent on the mainland, occur in the two regions. 



In presenting the following information at this time, it is realized 

 tliat to a considerable extent it is fragmentary, and that much 

 intensive work remains to be done; but it has been prepared in the 

 ho])e that such data as is available will be of sufficient value to 



