66 Nebraska Agricultural Exp. Station, Research Bui. 12 
RECOMMENDATIONS 
PLANT RESISTANT VARIETIES 
One of the greatest factors in controlling blister canker 
is to avoid planting trees which are known to be very suscepti- 
ble. It is inadvisable to plant susceptible varieties such as Ben 
Davis and Gano. These varieties will not prove resistant even 
under the most favorable conditions and are of poor quality. 
The Delicious is also a very susceptible variety but is of ex- 
cellent quality. Varieties such as Jonathan, Winesap, and 
Stayman will under average conditions live and produce 
heavily for a long time even after the heartwood has become 
infected. 
AVOID WOUNDS 
It is of the greatest importance to avoid making large 
wounds of any kind. This may be accomplished to some 
degree by training the trees while young. Small wounds in 
young trees are not nearly so easily infected as wounds ip 
old trees which expose wood several years old. If a tree is 
properly pruned and trained while young little pruning will 
be necessary after the tree reaches bearing age. 
PRUNE AT THE PROPER SEASON OF THE YEAR 
A little pruning will always be necessary even in well 
trained trees, but by doing this work at a time when there 
is the least liability to infection a great deal of the trouble 
may be avoided. It certainly is not advisable to prune dur- 
ing warm, wet weather. Summer pruning at any time is 
questionable where wood more than one year old is removed. 
DISINFECT AND COVER ALL WOUNDS 
Pruning wounds, even if made during the winter, may 
become infected unless protected by covers. All wounds which 
expose wood more than one year old should be covered. 
Suitable dressings and disinfectants aid very materially 
in preventing infection. Liquid asphaltum, and white lead 
and oil appear to be of about equal value. A tendency to 
blister may be overcome by making an application with the 
paint quite thin and later putting on a heavier coat. Both pine 
tar and coal tar are readily absorbed by the wood and allow 
the wood to check or crack. Considerable cambium injury 
may also occur. 
Copper sulphate has proved the most satisfactory disin- 
fectant owing to the fact that the tissues for a short distance 
