DISEASES OF PEARS 1045 



not to lea\e any unopened gashes, as infection may occur there. 

 All bark within the cut area must be removed so as to expose the 

 wood, but it is not necessary to cut away any of the wood. If 

 in removing the bark it is found that discolored bark remains, 

 this also should be cut away and the cut surface should be swabbed 

 out with a sponge or cloth saturated with a solution of corrosive 

 sublimate, made by dissolving one corrosive sublimate tablet in a 

 pint of soft water. This solution must not be kept in metal con- 

 tainers. It will be found convenient to carry an ordinary pint or 

 quart bottle of the liquid, to which a sponge is attached by means 

 of a long cord. Care should be taken to see that every part of the 

 wound is wet with this disinfectant. Germs can be carried on 

 the tools, but if the wound is disinfected every time a cut is made 

 no infection will result. After the wound has dried out, a pro- 

 tective covering of coal tar. will prevent decay of the heartwood. 

 This covering can be applied later in the dormant season if 

 desired. 



Since the bark of a young pear tree is smooth, cankers may 

 be readily detected. As the tree grows older, the outer bark 

 cracks and splits to accommodate the bark within. Oftentimes 

 these cracked areas greatly resemble fire-blight cankers. If in 

 cutting into such areas one finds healthy green .hark, it is an 

 indication that no canker exists. One should be careful always 

 to disinfect all cuts or other wounds made in healthy bark. Fire- 

 blight bacteria are known to produce superficial cankers, referred 

 to earlier in this bulletin, in which only the outer bark becomes 

 affected. As they do no special harm, these should not be re- 

 loved. No matter how much like a canker a certain area on the 

 surface may -appear, it should not be cut away if there is green 

 or white tissue beneath. If, however, it is discolored red, brown, 

 or black, whether due to fire blight, winter injury, or other 

 causes, it should be removed and treated as described above. Fruit 

 spurs coming from the body and large limbs should be broken off, 

 as they are a frequent source of canker. 



The removal of sources of infection in and about one's orchard 

 is a big step toward the control of fire blight, but as long as such 

 sources exist in the neighborhood one cannot hope that infections 

 will not occur. In order to reduce the danger of fire blight to 

 a minimum, an entire community should take action against it. 



