64 JOURNAL OF AGRICULTURE OF P. R. 



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lowiui,' treatment the roots should be left exposed for a time at 

 least, and preferably, treated portions should not be recovered 

 at all. 



In addition to eutting away infected bark, all discolored wood 

 should likewise be removed with a gouge, or chisel, although this 

 is not so vitally necessaiy as the first step. The instrument used 

 in this work should be sterilized at frequent intervals by dipping 

 in disinfecting solutions (see appendix). All diseased bark and 

 wood should be removed from the groves and destroyed. 



"When the wound has been thoroughly cleaned, it should then be 

 protected against reinfection. As a preliminary treatment Bordeaux 

 paste (see appendix for formula) is ordinarily recommended, and 

 is efficient, a thick coating being applied over the entire wound 

 surface. After a week or ten days some permanent covering is nec- 

 essary, and for this purpose gas tar is recommended, although there 

 are other substances that serve the same purpose more or less effi- 

 ciently. This phase of the subject is discussed more fully under wood 

 rot. In the majority of eases there is no reason why the tar could 

 not l)e applied without the preliminary treatment, delaying several 

 days until the wound has dried out somewhat. Where entire roots 

 have been cut away in the Mork of eliminating infected areas, a cor- 

 responding cut in the top will be desirable. 



This line of work properly carried out (and it is utterly valueless 

 unless it is properly performed) is an expensive operation, and should 

 not be undertaken when the disease has made any great headway. 

 A common rule of thumb is to take out all trees more than hall' 

 girdled. The loss in yield in seriously deseased trees, combined with 

 the expense of treatment, make it preferable to replant. 



As with many other diseases, much can l)e done in the way of 

 prevention, and it should be the ultimate aim to control by tliis incaiis, 

 rather than by the more laborious and expensive cutting-out method. 

 In this connection one of the most successful factors is the use of 

 resistent stocks. As noted, lemon and to a less extent sweet orange 

 roots are most susceptible. Sour orange and grape fruit, on the 

 other hand, are very resistent. A few cases of disease have been 

 noted on grapefruit, but it is thought that it will prove satisfactory 

 as a stock, although it has not been in general use in Porto Rico suf- 

 ficiently long to judge its ultimate behavior. To avoid foot rot, then, 

 sour orange or grapefruit stocks should be used, particularly when 

 planting in low lands, or Avhere the disease has been prevalent. 



