354 MANUAL OF TREE DISEASES 



sary except that it should be left so that it will not hold water. 

 The bottom should slope outward at a sharp angle from all 

 directions. After the removal of all the diseased wood, the 

 surface of the cavity should be covered with a good wound 

 dressing (see page 348). In the case of cavities in which a 

 large amount of heartwood is exposed, the wood can very ad- 

 vantageously be painted with creosote or carbolineiun. This 

 will serve excellently as a penetrating and permanent disinfect- 

 ant. Then one or more coats of a dressing such as asphaltum 

 (heated to liquid condition) or coal-tar should be applied. After 

 such treatment the work is finished so far as remedying the dis- 

 eased condition is concerned. The diseased part of the tree has 

 been eradicated and the wounded surface protected. There are 

 several additional steps often taken which are non-essential and 

 even harmful to the success of the work. In other words, cavi- 

 ties are better left open. The orchardist, especially, should 

 never spend money filling cavities or even tinning them. If 

 the cavity is left open, it can be inspected yearly and any neces- 

 sary renewals of the dressings made. The only advantage 

 claimed for tinning cavities is that the holes are closed up, the 

 tree appears normal in shape and the metal furnishes a support 

 for the developing callus. In the case of narrow slit-like cavities, 

 this may eventually result in complete healing over. 



Tinning is not to be advised on large cavities. It is mainly 

 advantageous for those which may be expected to heal ulti- 

 mately. The main benefit derived from the tinning is the sup- 

 port of the callus which would otherwise roll inside the cavity. 

 The disadvantage of tinning is mainly that the surface of the 

 cavity is no longer visible. The opening of the cavity must be 

 so shaped that the metal will lie without wrinkling. Also a 

 band of bark, about one-half to three-quarters of an inch wide, 

 must be removed so that the metal may be seated on the wood 

 and nailed fast. The metal should be placed even a little below 

 the inner surface of the bark. Zinc and copper are the best 



