2 CIRCULAR 65 6, IT. S. DEPARTMENT OF AGRICULTURE 



The ideal dressing should be noninjurious to cambium and should 

 protect the exposed wood against decay-producing organisms during 

 the several months required for healing. It should not melt and run 

 in summer or become hard, crack, and flake in winter; it should 

 adhere to fresh wounds and be easily applied; and it should be suffi- 

 ciently porous to let excess moisture evaporate from the wound 

 beneath it. For use in connection with certain diseases, the ideal 

 dressing should be toxic to the causal organism but should not injure 

 the host. For example, while working with the fungus that causes 

 a killing disease of planetrees and sycamores, Walter and Mook 

 (15) 2 found that asphalt dressings that killed the causal fungus also 

 killed the cambium and that certain asphalt dressings were not anti- 

 septic and might transmit the causal fungus. 



This circular reports studies on the development and evaluation 

 of wound dressings and the effects on callus formation of a number 

 of different types of wound dressings applied to fresh wounds on 

 apple trees and also of the effect of season of wounding upon the 

 healing of the wounds. An attempt was made to discover treat- 

 ments that did not kill the cambium around the wounds on apple 

 trees and thus enlarge them and to learn the time of year when apple 

 tree wounds form callus most readily. The work was begun in con- 

 nection with studies on the perennial canker of apple trees, caused 

 by Neofabraea perennans (Zeller and Childs) Kienholz. It was carried 

 on at Hood River, Oreg., from. 1929 to 1931 and was continued from 

 1931 to 1938 at Arlington Experiment Farm, Arlington, Va. 



REVIEW OF LITERATURE 



The literature on wound dressings indicates that their use has 

 been aimed principally at preventing the entrance of disease-producing 

 organisms at wounds. 



Brooks and Moore (2) showed that it was very difficult to prevent 

 invasion of the silver leaf organism by an application of a fungicide 

 to the wound. They tested many old preparations and also devised 

 a number of new ones, but their preparations usually either did not 

 kill the pathogen or killed too large an area on the treated plant. 

 Brooks (1, p. 272) finally recommended soft grafting wax or a white- 

 lead paint. 



Howe (8) investigated the healing of apple tree and peach tree 

 wounds treated with shellac, white lead, yellow ochre, white zinc, 

 and avenarius carbolineum. He reported impaired healing with all 

 treatments except shellac and stated that many of the commonly 

 used dressings did more harm than good because of their toxic effects. 

 He obtained nearly as good healing where shellac was used as where 

 the wounds (check) were unpainted. 



Zeller (16) recommended bordeaux paint made by stirring raw 

 linseed oil into a commercially prepared bordeaux dust. He contended 

 that one of the chief advantages of this dressing is that it is 

 sufficiently porous to allow evaporation of the exuded sap. 



The early literature on wound dressings was reviewed by Marshall 

 (9), who reported that wounds on certain forest trees healed better 

 if given a coat of shellac than if left untreated. His work also em- 



2 Italic numbers in parentheses refer to Literature Cited, p. 18. 



