10 CIRCULAR 2 3 7, U. S. DEPARTMENT OF AGRICULTURE 



be obtained from insecticide dealers. Rosin residue is the sticky 

 resinous material that remains in the stills after the distillation or 

 rosin. It is available on the market in three grades and may be 

 obtained from dealers in naval stores. 3 



A 50-percent emulsion of rosin residue is prepared as follows: 

 4 pounds of casein is dispersed in about 45 pounds of water to which 

 12 ounces of ammonium hydroxide (specific gravity 0.90) has been 

 added ; 50 pounds of rosin residue is added slowly with violent agi- 

 tation, which is continued until the material becomes emulsified. 

 This emulsion can be diluted without difficulty with hard, cold water. 

 In preparing this spray, the rosin-residue emulsion is added to the 

 water in the spray tank, and a thin paste of the derris is poured into 

 the mixture. 



The first application of the spray should be made when the beetles 

 first appear in the orchard. Subsequent applications should follow 

 at intervals of 7 to 10 days, the number necessary being dependent 

 upon the degree of infestation. 



LATE PEACHES 



The fruit of varieties ripening at the same time as or later than 

 Hiley is seldom eaten by the beetle, but the foliage of late-ripening 

 varieties is often severely injured, and, unless protected, the fruit may 

 be of poor quality. The foliage on these varieties and on young 

 trees that have not come into bearing can be protected with the lime- 

 aluminum sulphate spray. Because of the objectionable residue left 

 by this spray, not more than two applications should be made. 

 Under no circumstances should the trees be sprayed after July 15, as 

 considerable residue will be on the fruit at the time of harvest. 



PLUMS 



The spray of derris-rosin residue emulsion is recommended for 

 early-ripening varieties, and that of hydrated lime-aluminum sul- 

 phate for the late varieties. 



CHERRIES 



The cherry crop is usually harvested before the Japanese beetle 

 appears in sufficient numbers to injure the foliage or fruit. After 

 the fruit is harvested, an application of 6 pounds of lead arsenate and 

 4 pounds of flour in 100 gallons of water is recommended for the pro- 

 tection of the foliage. When leaf spot or yellow leaf is present in 

 the orchard, 2% gallons of commercial lime-sulphur solution should 

 be added to the mixture. It may be necessary to repeat the applica- 

 tion 2 or 3 weeks later. 



8 The physical constants of the grade of rosin residue most satisfactory for use in 

 peach sprays are as follows : 



Melting point °C__ 30 



Specific gravity at 25° C 1.03 



Viscosity, Sayholt, at 100° seconds— 100-200 



Acid number . 50-75 



Saponification number 89 



Unsaponifiable percent — 50 



Petroleum-ether soluble do 3. 8 



Volatile with steam at 230° do 25-35 



