6 FRI/IT TREE CANKERS AND THEIR CONTROL. 
Cankers sometimes are found on nursery stock. Whenever 
nursery stock is purchased, therefore, it should be thoroly 
inspected by the grower before being set out. Any suspicious 
looking cankers should be examined by a competent person and 
if they prove to be of a dangerous nature the tree should not be 
planted. 
After cankers are once established, they can be controlled 
only by tree surgery. Regardless of the origin of the canker, 
the general principles of control ought always to be the complete 
removal of the dead areas. Whenever small branches have seri- 
ous cankers they should be cut off far enough below the external 
visible indications of the canker to insure getting rid of all dis- 
eased material. Whenever branches are cut, the cut should be 
made parallel with the surface of the part of the tree from which 
the branch is growing. This may sometimes make a longer cut 
but healing will be more rapid if the wound is properly made, 
even though it may be larger. The surface should always be 
smooth. Jagged surfaces allow water to accumulate and make 
the process of healing difficult, and also allow the entrance of 
wood-rooting fungi. Long stubs should never be left. They 
are often the source of much annoyance and danger. If the 
wound is large it should be properly protected. If it is small, 
that is, not over an inch and a half in diameter, it will usually 
callous over if properly made. When cankers occur on very 
large limbs or on the trunk it may not be advisable to remove 
the entire limb or the entire tree. The canker can quite often 
be cut out. (See Fig. V.) Whenever this is done the cut should 
be long and pointed at both ends in order to aid in healing. The 
work should be done with a very sharp knife and the cut should 
be perpendicular to the bark, not slanting. (See Figures V2 
and V3.) All dead wood should be removed. If it is not, the 
canker will continue to spread. After the removal of the dead 
area the wound should be protected. (See Figure V4.) 
WOUND COVERINGS 
Whenever large wounds are made either in cutting out 
branches or cutting out cankers on large limbs or trunks, they 
should be properly protected. A good wound dressing ought to 
be cheap and easy to handle and should be a disinfectant as well 
