12 Department Circular 2GS, U. S. Dept. of Agriculture. 



Practically all scales on the fruit of Plats 1 and 2 were killed by 

 the action of the oil emulsion, the only scales escaping being located 

 deep in the calj^ces. Live scales on the fruit of the other three plats 

 were plentiful. 



The results of this late suimner treatment demonstrate that a fair 

 percentage of the scales can be killed with oil emulsion if cool 

 weather prevails. Much damage from the scale has resulted in this 

 section in former years during the period from the middle of Sep- 

 tember to the middle of November. 



ADVANTAGES AND DISADVANTAGES OF OIL EMULSION. 



The low cost of lubricating-oil emulsion appeals strongly to or- 

 chardists. Another advantage of oil emulsion is the fact that hired 

 hands will do a better job of spraying with this solution than they 

 would with more caustic insecticides. They are not so cautious 

 about dodging the spray when it does not burn the face and eyes. 

 Oil emulsion also leaves the spray-rig in much better condition 

 after an application than is the case with many insecticides. Some 

 growers even consider that a saving in spray material follows from 

 the spreading power of the oil spray. It is not advisable, however, 

 to attempt a saving of spray solution in fighting a bad infestation 

 of the scale. 



Some trouble has been encountered in the Ozark region because 

 the stock emulsion would not mix readily with the water that was 

 used for spraying. Oil is set free in some instances when hard 

 water is used for spraying. Free oil in the spray tank appears as 

 a thick greenish scum on the surface of the dilute solution. A weak 

 Bordeaux mixture, used at the rate of i-i-50, will overcome this 

 difficulty. This weakened Bordeaux has never failed to make the 

 hardest water of this section mix with the stock emulsion. AAlienever 

 available, soft water should be used with the oil emulsion. 



The presence of lime-sulphur residue in the spray tank and spray 

 pump has been responsible for some of the difficulty experienced in 

 obtaining a proper emulsion. A small amoimt of lime-sulphur will 

 set the oil free. Any lime-sulpliur residue present in a spray-rig 

 should be cleaned out by running a strong solution of caustic soda 

 or lye through the pump and washing the inside of the spray tank 

 before the oil emulsion is used. Even then it is ad\dsable to use the 

 weak Bordeaux mixture in the first tank or two. 



Precaution should be taken to prevent the stock emulsion from 

 freezing, which occurs at a temperature of about 15° F. If suffi- 

 cient shelter is not available to protect barrels of oil emulsion during 

 cold weather, they should be thoroughl}^ covered with sti-aw or other 

 suital>le material. ^^Hien the stock has once l)een frozen the emul- 

 sion will break down and become unfit for later use. ' 



SPRAY INJURY. 



The possibility of injury was one of the unknown factors in the 

 use of oil emulsion on apple trees. From experience with this in- 

 secticide in commercial citrus groves in Florida, where an emulsion 

 containing 1 per cent of oil has been used on trees in foliage for a 

 number of years, it was felt that an emulsion containing 2 per cent 

 of oil would be safe on apple trees during the dornnint season. The 



