WHAT 18 BEING DONE TO COXTltOL CANKER 63 



It might be inferred from this tliat it is a bad practice to prune. It 

 is, where it is done in tlie careless "slipshod" method I have often ob- 

 served, of chopping- the branches off with an ax, sawing from the top 

 and allowing the bark to peel down, leavins? stubs all the way from one- 

 half inch to six inches long, cutting into a cankered tree, then going 

 right ahead to a new tree with the tools all covered with spores and 

 never covering the wounds. If the work is done this way, the trees would 

 be much better off if left unpruned. Careful, judicious pruning must be 

 done and does not injure any tree, but is a means of producing more 

 and better fruit. 



It sometimes requires several seasons for the disease to destroy 

 a limb, especially if it is a large one. At first, the diseased area may 

 be comparatively small, but it gradually extends farther and farther 

 up and down the branch, as well as around it. I have observed these 

 cankers extending down one side of a large limb and the trunk to the 

 ground and affecting the roots. A peculiarity of this disease is that only 

 a small area of the bark at the point of infection may be affected but 

 the mycelium goes deep into the heartwood and travels both up and 

 down the limb, coming to the surface again some distance away, espe- 

 cially if the limb is injured at some other point. The progress of the 

 disease is marked by a dark brown discoloration of the fibers. It is 

 this rapid growth in the heartwood which makes it so difficult to con- 

 trol. 



The increased loss each year, due to this disease, has shown the 

 necessity of securing some means of controlling or preventing it. The 

 stations of Ohio, Illinois, Iowa, Kansas and Nebraska have perhaps done 

 the most work along this line. The methods used so far have proved 

 beneficial but no specific remedy has been discovered. Professor W. O. 

 Gloyer of Ohio station has performed some interesting experiments in 

 which he shows that branches from which about 20 per cent of the wa- 

 ter was driven off were most easily inoculated with the disease, and 

 that a certain amount of oxygen was necessary for development. This 

 was borne out by the fact that in Nebraska at least, trees which have 

 suffered most from winter injury and drouth show the greatest amount 

 of canker, and that infection is oftenest found where stubs have been 

 left in pruning or where a large wound was left uncovered. In either 

 case the amount of water is materially less and oxygen naturally pres- 

 ent. 



We must consider this depletion of water and the presence of oxygen 

 in looking for a remedy. It is necessary first to remove the portion of 

 bark and wood infected; second, to use some disinfectant to destroy any 

 spores which may be present in the wound made; third, to use some 

 sort of a dressing for the wood which \\''ill prevent the loss of sap, and 

 consequently drying out, wiiich will exclude air, and which is cheap 

 enough to not be prohibitive. 



All the work done up to the present time has been along this line, 



