46 JOURXAL OF AGRICULTURE OF P. R. 



the wild orange crop this estimate is very low, the loss from shipping 

 rots alone commonly amounting to ten per cent, and often going as 

 high as fifty. 



The need for investigation of the citrus diseases was recognized, 

 and immediate attention given, following the turning over of the 

 present Insular Experiment Station to the Government by the Sugar 

 Producers' Association. Progress reports and publications have been 

 issued from time to time on certain phases of the problems investi- 

 gated. These are noted in the bibliography on page 110. 



As the work has progressed it has become apparent that, consider- 

 ing the groves as a whole, there is taking place a gradual spread of 

 the various diseases, and that certain ones are becoming more virulent. 

 Several have been discovered of comparatively recent introduction, 

 or at least of recent activity on citrus hosts, and these may at any 

 time assume a virulent state. The increased plantings, for the most 

 part of one species, the grapefruit, and often in practically continuous 

 stretches, tend to favor the increase and spread of injurious fungi. 



The entire subject then, and particularly the matter of control 

 measures from the grower's view point, becomes increasingly im- 

 portant. Many who have in the past ignored or given scant atten- 

 tion to the matter of grove sanitation, spraying, and improved 

 cultural conditions, are now confronted with the vital necessity of 

 prompt action along these lines. 



While much has been accomplished in disease control in other 

 citrus-producing regions, we find that recommendations applicable 

 there often fail to give results under Porto Rican conditions, and it 

 becomes clear that our disease problems must be worked out in large 

 part here. The life histories of the various fungi involved and the 

 principles of control can be studied out in the laboratories, or in such 

 field experiments as are possible, l)ut the practical working out of 

 control measures lies very largely in the grower's own hands. 



Citrus diseases not present in Porto Rico. 



Althougli Porto liico has an all-too-long list of diseases present 

 in the groves, there are still a considerable number of diseases, 

 recorded as serious, which exist in other parts, of the world and have, 

 not yet reached the Island. 



Probably the best known of these at the present time is the canker, 

 a most virulent bacterial disease of leaves, fruits, and young twigs, 

 which was aecidently introduced from Japan into a number of the 

 Southern States some years ago. Several millions of dollars have 



