454 BOARD OF AGRICULTURE. [Pub. Doc. 



the wound Avith new wood and bark. For this purpose a 

 lasting and antiseptic dressing is required. Coal tar was 

 used almost exclusively in the gypsy moth work. It is 

 inexpensive, penetrates the wood, adheres well, lasts well, 

 and its odor is repellant to insects. Large wounds given 

 one coat of coal tar in November, 1895, are, some of them, 

 still (July, 1902) in a fair state of preservation. 



The objections to its use are, that it must be warmed in 

 cold weather, that it is more difficult to apply than paint, 

 and that it may injure the bark if applied so as to come in 

 contact with it. DesCars says that coal tar should only be 

 used with caution on the wounds of drupaceous fruits (cherry, 

 peach, plum, etc.) ; Card states that coal tar seems to have 

 hindered the healing process ; * Bailey says that coal tar 

 often injures the cambium and bark of fruit trees ; t while 

 Hartig, who experimented mainl}^ with oaks, says, "I have 

 never observed any injurious cflect of the tar on tissues ; " 

 also, " It is only the ruptured organs and their walls that 

 are penetrated and impregnated by the tar." :i: 



It is a matter of common observation that tar applied 

 copiously and directly to the bark of fruit trees may cause 

 injury. Some of our observers affirm that if applied on 

 newly formed callus it injures the cells and checks new 

 growth. It should be used, therefore, with care, for its 

 office is to coat the exposed wood, and not the bark. The 

 tar when dry does not injure the callus, which grows over 

 it precisely as it does over unprotected wood. 



If green branches, larger than one or two inches in 

 diameter, have been removed, it may become necessary the 

 second year or later to apply another coat of thick tar, to 

 fill any small cracks resulting from the drying of the wood. 

 Then the utmost care should be exercised to keep the fresh 

 tar from touchino; the rino- of callus which has formed 

 about the wound. Thick lead or asbestos paint may be 

 used in place of tar. The only objections to their use are 



* " Notes on pruning," Bulletin No. 50, Nebraska Agricultural Experiment 

 Station, 

 t "The pruning book," L. H. Bailey. 

 t " Diseases of trees," R. Hartig. 



