Apr. lo. 1916 Citrus Canker 95 



certain birds and insects also effect this contact of diseased with healthy 

 parts and are therefore to be regarded as agents in dissemination of 

 Citrus canker. 



CONTROL OF THE DISEASE 



During the summer of 191 4 those who had been attempting to solve 

 the problem of controlling Citrus canker realized that it was an exceed- 

 ingly difficult undertaking. Efforts were directed along three lines: 

 Exclusion, protection, and eradication. 



Exclusion. — Those interested in the welfare of the Citrus industry in 

 Florida were the first to realize the serious nature of Citrus canker and 

 that it had been introduced into the State from other States and from 

 foreign countries. For these reasons a quarantine was imposed during 

 the spring of 191 4 to prevent the further introduction into Florida of 

 Citrus trees and buds and thus of Citrus canker. Other of the Gulf 

 States later in the season realized the jeopardy in which their Citrus 

 growers' interests were placed and issued similar regulatory measures on 

 the importation of shipments of Citrus stock. On January i, 191 5, a 

 Federal quarantine was imposed to exclude the further importation of 

 this disease into the United States. The agitation throughout the entire 

 Citrus growing section of the Gulf coast attendant on the adoption of 

 these regulations looking toward control by exclusion have so familiar- 

 ized the growers with Citrus canker that it is unnecessary to advise the 

 exercise of care in ordering trees to be used in setting out a Citrus grove. 

 It is reaUzed that in no case is it safe to purchase trees from nurseries in 

 which this disease occurs. 



Protection. — Since certain fungicides have been successfully used in 

 the control of various Citrus diseases a number of experiments were 

 undertaken during the spring of 1914 to determine the effectiveness of 

 these mixtures in the control of Citrus canker. A grove of badly dis- 

 eased grapefruit was used upon which to make applications of Bordeaux 

 mixture, ammoniacal copper carbonate, and soluble sulphur. Details of 

 these experiments are withheld, since it was reaUzed early in the summer 

 that the appHcation of these fungicides was without appreciable effect in 

 the control of canker. 



Again in the spring of 191 5 another grove of grapefruit was selected 

 in which to test the effectiveness of several fungicides in protecting the 

 trees from infection by the canker organism. All visible signs of canker 

 were carefully removed from the trees prior to the application of the 

 mixtures. Bordeaux mixture, Bordeaux mixture and bichlorid of 

 mercury (12 tablets in 3 gallons), Bordeaux mixture and formaldehyde 

 (i : 100), and a Bordeaux and lead arsenate mixture were employed. 

 Applications were made on March 26, April 29, and May 14, and no new 

 infections had developed on any of the sprayed or unsprayed trees by 

 the last-named date. On May 27, however, new infections were apparent 



