88 PROTECTION OF PLANTS, 1915-16 



Another method of control, or rather prevention, is to keep the trees 

 healthy by thorough and clean cultivation, since it has been found that 

 vigorous trees are less susceptible to attack; and also to remove any wild 

 varieties of plum and cherry that may be in the neighborhood. Nothing, 

 however, has been found so effective, so easy and so economical as good 

 sharp pruning tools. These used freely with a reasonable amount of intelli- 

 gence will readily and efficiently control all cases of the Black Knot of plum 

 and cherry. 



