WOUND DRESSINGS ON APPLE TREES 5 



Dressing No. 540 was prepared by heating the rosin with the sardine 

 oil until the rosin melted, then cooling until the addition of a few 

 drops of water caused no spattering, and then adding the soap, which 

 was mixed in by stirring and cautious heating until the wax was a 

 homogeneous mass. Dressing No. 541 was prepared by heating to- 

 gether the rosin and the fish oil. 



Copper soap may be purchased from a marine products or chemical 

 supply company, or it may be made as follows: Dissolve 1 pound of 

 potassium hydroxide in 1 quart of boiling water, add slowly 5H 

 pounds of fish oil while stirring vigorously, and continue heating until 

 a smooth soap is formed; dilute with l / 2 gallon of water and add 2 

 pounds of copper sulfate dissolved in K gallon of hot water; continue 

 heating until the copper soap separates out and the liquid has lost 

 most of its blue color. When cool, decant the liquid. This should 

 leave not more than 12 pounds of soap. There is a great difference 

 in the saponifying properties of different fish oils. Salmon oil has 

 proved very satisfactory. 



Many of the substances and combinations used in the experi- 

 ments reported are poisonous. Therefore potential users unfamiliar 

 with them should ascertain their toxic properties and store their stock 

 supplies or dispose of surplus mixtures where they will be out of 

 reach of children and animals. 



EXPERIMENTAL TESTS OF DRESSINGS 

 Materials and Methods 



Early in the study of wound dressings differences were found in 

 injuries caused by dressings of the same formula but made and 

 applied at different times. Later, it was noted that the same batch 

 of material caused different amounts of injury when applied at dif- 

 ferent seasons of the year. In November 1930 experiments were 

 started to obtain more information on the effect of the seasonal-growth 

 cycle on treated wounds and on callus formation and to determine 

 the effectiveness of a fungicide in a wound dressing. 



At Hood River, Oreg., wound dressings were applied immediately 

 or at definite later periods to pruning wounds made in early spring 

 during the usual pruning operations on apple trees. Also apple trees 

 were wounded and treated at different times during the year. The 

 work was later repeated at Arlington Experiment Farm, Arlington, Va. 



All the apple trees used, in both Oregon and Virginia, were more than 

 20 years old and lacking in vigor. They were named varieties, but as 

 variety was considered unimportant, results for all varieties were 

 combined. The trees developed callus very slowly, and the least 

 vigorous ones were more injured by slightly toxic dressings. Such 

 weak trees are the type on which develops the most trouble in pruning 

 wounds in general orchard practice. 



All the wax preparations were applied at the consistency of a thick 

 paint, this being obtained either by warming with a grafting lantern or 

 by diluting with a solvent such as gasoline. The preparations used 

 were (1) dressing No. 540 (p. 4), (2) dressing No. 541 (p. 4), (3) 

 white lead and raw linseed oil as a thick paint, (4) No. 540 with gasoline 

 as a thinner, (5) No. 541 with gasoline as a thinner, and (6) shellac. 

 During the first year at Arlington Experiment Farm supplemental 



