Blister Canker 
67 
beneath the surface of the wound retain the copper for a long 
time. 
PREVENT DISSEMINATION OF SPORES 
By scraping away and burning all cankered bark from 
infected trees or by covering all cankered surfaces with a 
coating of heavy paint or liquid asphaltum a great deal of 
infection may be avoided. In the first case the spores are 
destroyed and in the second they are prevented to some extent 
from escaping. Unless treated in this way all cankers should 
be thoroly painted or sprayed with copper sulphate at the rate 
of 1 pound to 2 gallons of water, early in the spring before 
the dissemination of spores begins. This should also prevent 
to some extent the formation of new spores. 
It would also be well when applying the regular orchard 
sprays to cover thoroly all parts of the tree. This would offer 
some protection from canker infection. 
When a cankered limb ceases to bear profitably it should 
be cut off and burned. As soon as a tree becomes so badly dis- 
eased that it is no longer profitable it should be removed from 
the orchard and burned. 
New trees may be planted to fill vacancies. There is little 
danger of their becoming infected thru the roots if one or two- 
year-old trees are used and the roots are not cut back severely. 
(ll-3-'17 — 5M.) 
