CITEUS DISEASES. 73 



infection. There are many means by which wounds may be produced, 

 including those caused by mechanical agencies such as hoes, or other 

 instruments or machines used in cultivation, animals, and sunburn. 

 Injuries from tliese soui'ces are commonly taken care of, but these 

 resulting' from the attacks of parasitic fungi are but seldom given 

 proper attention. Foot-rot gives excellent opportunities for the en- 

 trance of wood-rot, and similar results follow attack by the pink 

 disease (Corticium salmonicolor) , psorosis, Diplodia branch and trunk 

 cankers, and other trunk diseases. 



A third source of wounds occurs as a result of routine pruning 

 operations. Faulty or careless work, the leaving of stubs which delay 

 or prevent healing, combined with improper treatment, or none at 

 all, make this class of wounds the most common point of entrance 

 for decay. 



As a general rule the rebudding or top working of citrus trees in 

 Porto Rico has not been successful, and there can be but little doubt 

 but that wood rot, following sunburn of unprotected branches and 

 trunks, and untreated or poorly treated pruning wounds, will explain 

 in large measure the poor results obtained here from a system so 

 successfully carried out in other citrus regions. 



Treatment and prevention. 



Under the head of treatment, little need be said. For while it 

 is ([uite possible to apply the usual methods of the tree surgeon to 

 infected trees, it is not advisable from a practical standpoint under 

 Porto Rican conditions. The expense of cutting out diseased wood, 

 filling cavities, putting in braces, and caring for other details would 

 be prohibitive. Treatment is advised only in incipient cases, or 

 where the entire diseased area can be readily reached. This will 

 practically apply only to sap-wood or bark-rot. A word of caution 

 is necessary with regard to attempts at treatment. The removal of 

 part of the rotted wood, only, the part that can be reached readily, 

 for instance, and the scaling over of the wound will prove of no 

 avail, liut on the contrary will permit the decay to progress more 

 rapidly than otherwise, since the wound can not dry out. Moisture 

 is H re((uisite for decay. 



Ft is recommended as a practical and economic measure that trees 

 badly diseased or unthrifty because of wood rot, or any other cause 

 for that matter, be dug up and replaced with healthy trees from the 

 nursery. 



It is to prevention that most attention must be given. Siniply 



