160 rRINCIPI.ES AND PRACTICE OF PRUNING 



surfaces least well of all. Avenarius carbolineum and yellow ocher 

 caused so much injury that neither substance should ever be used 

 (compare 134). Coal tar not only caused injury, but quickly dis- 

 appeared, either through absorption or evaporation. 



White lead and white zinc caused some injury at the time of 

 application, but the wounded tissues recovered rather quickly, and 

 at the close of the first season the injury was not very marked ; at 

 the close of the second season it had nearly disappeared. These two 

 paints are the best of the protective substances used, and of the two, 

 white lead is the better. 



Nothing is to be gained in the treatment of wounds by waiting 

 several weeks before applying any of the various dressings used in 

 these experiments. 



The treatment of peach tree wounds with any of the substances 

 under experiment caused so much injury that it may be said that 

 the wounds of the peach should never be treated with any of them, 

 and it may be inferred that this is true of wounds on trees of all 

 stone fruits. There is nothing to show in this experiment that it is 

 worth while to treat large or small wounds of tree fruits with any 

 of the substances in common use. Had there been a longer period 

 of observation, it might have developed that the wood exposed in 

 the larger wounds would have been somewhat saved from the decay 

 which often sets in on exposed wood of fruit trees. It may prove 

 to be worth while, therefore, to cover large wounds; in which case 

 white lead is undoubtedly the best dressing to use. 



From the results of this experiment several deductions seem war- 

 ranted. First, the dressings commonly applied to pruning wounds 

 retard rather than accelerate the healing of the wounds. Second, 

 the effects are the same whether the dressings are applied when the 

 wounds are made or some weeks later when the cut surface has 

 dried out. Third, the effects of the dressings used are so injurious 

 to peach wood that wounds on peach trees should never be covered. 

 Probably this statement holds true for other stone fruits as well. 

 Fourth, these experiments suggest that the popular notion that 

 wounds need to be covered with some dressing to prevent the en- 

 trance of fungi, in sprayed orchards at least, is usually exaggerate I. 

 It is doubtful if it is necessary to attempt to pre\'ent decay b.y appli- 

 cations of dressings of the kinds under discussion in woimc's under 

 4 or 5 inches in diameter. It remains to be proved wdicther they 

 have any real value in covering large wounds. It maj' be s'.:s"ec el 

 that the injury caused by the dressing when applied to the wounds 

 largely, if not wholly, offsets or even o\'er-l)alances the protection 

 offered, if there be such, against decay. 



134. Painting tree wounds. — The statements quoted from the New 

 York Experiment Station bulletin above, prompted Howard B. Cook 

 t'l publish in the Country Gentleman* an article from which the fol- 

 lowing passages are condensed, Mr. Cook agrees that peach 



• May 6, 1916, Page 988, 



