84 JOUENAL OF AGEICULTUEE OF P. E. 



many thousands of dollars, including not only that caused by the 

 immense quantity of fruit consigned to the cull pile, hut that which 

 comes from placing in the lower grades all that is disfigured by 

 the disease. 



Citrus seal) is an introduced disease, which has been present many 

 years, probably having been introduced originally from Florida, it 

 first appeared on the sour orange and lemon, particularly on the 

 seedlings of these varieties in nurseries, but as they were of no 

 economic importance or were soon budded over to the immune orange 

 or grapefruit, no attention was paid to the disease. 



This was the status of affairs until the excessively wet season of 

 1911-12, when the grapefruit was attacked suddenly, and in the 

 most severe fashion in the Bayamon section. Since that date there 

 has been no decrease in virulence, and furthermore most of the 

 other citrus districts have been invaded in turn. 



Varieties attacked. 



As has been noted above the sour orange (Citrus aurantium), 

 and the rough lemon (Citrus limonia var.) have always been es[)e- 

 cially subject to attack, it being quite usual for one hundred per cent 

 of seedlings in the ni;rsery beds to be badly distorted and stunted. 

 The other varieties of the lemon according to reports, were equally 

 diseased at the time when they were grown in commercial groves 

 here. 



Shoots from the lemon roots of grapefruit trees are very subject 

 to scab attack. 



The .lime (Citriis aurantifoUa) . the satsuma, and the mandariji 

 (Citrus nohilis var.) have not been noted as susceptible in Porto Rico. 

 The king orange (Citrus nohilis var.) is attacked, ])ut not seriously. 

 The kumquat (Citrus japouica) is free of the disease in so far as 

 known. 



The sweet orange (Citrus sinensis) is usually considered as im- 

 mune, but in several instances trees have been found bearing a few 

 scabby fruit, generally when in close proximity to diseased sour- 

 orange trees. It is, however, considered not at all unlikely that it 

 may lose this immunity at any time, as has but recently hrippened 

 in the case of the grapefruit. 



Of the grapefruit (Citrus decumana) , three principal types are 

 grown in Porto Rico on a commercial scale, the Duncan, the Marsh's 

 seedless and the Triumph. The latter has at all times been imnuine, 

 with the exception of slight infections found on seedlings. Because 



