8 
FRUIT TREE CANKERS AND THEIR CONTROL. 
as a preservative. Paint is often used in Minnesota orchards 
but is not very satisfactory. Recently coal tar has been used 
very successfully. Coal tar can be obtained from the local gas 
company and is cheap and easy to handle. 
TREE. SURGERY FOR WOOD ROTS 
When any part of a tree has begun to rot the decayed por- 
tion should be remqved. Unless a person is experienced in this 
kind of work it may be well to procure the services of a reliable 
tree surgeon. The general principle to be followed, however, is 
the same as that to be followed in the excision of cankers. All 
of the rotted portion should be removed. After the removal of 
the rotted wood the tree should be strengthened by some wound 
filling. Dry sawdust and asphaltum have been used successfully. 
The cavities made are filled with the mixture in the proportion 
of one part asphaltum to from three to six parts of sawdust. 
Tree cement is often used, but is so rigid that it is sometimes 
undesirable. 
Prompt attention to canker control may save considerable 
trouble in the future. Watch your trees carefully. Whenever 
cankers appear cut them out, in order to protect the rest of the 
tree and the rest of the orchard. Burn all diseased material to 
prevent the spread to other trees in the orchard. Control dis- 
eases, protect wounds, prune the trees properly, and do not 
let cankers get started. Keep them in check. When an orchard 
is once badly infested with cankers and wood rots, the work of 
cleaning up is rather discouraging. It is much easier and more 
economical to prevent the development of cankers than to remove 
them after they have once become established. Conditions are 
rather serious in Minnesota now because of the attacks of fire 
blight during 1913, 1914, and 1915, resulting in much dead wood. 
Black rot cankers followed very closely on the attacks of fire 
blight, and wood rots are following closely on the attacks of black 
rot. Clean up the orchard now and keep it clean in the future. 
For further information write Plant Disease Department, Uni- 
versity Farm, St. Paul. 
