ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



69 



spray hose at about 250 pounds' pressure into empty drums for storage 

 until it is used. A second pumping is advisable if the emulsion is 

 to be kept more than a week or so. The emulsion should not be 

 made during freezing weather, but when once made it will stand the 

 ordinary temperatures occurring after March 1. It should be used 

 as soon as possible after making, although it will usually keep for 

 several weeks in closed drums. The cost of making, aside from the 

 cost of the oil, should not be over 2 cents per gallon. 



The methods of preparing emulsions for dormant and summer use 

 are the same, except that different oils are needed for the two pur- 

 poses. The grower should be sure that the proper oil is employed, 

 whether he makes his own emulsions or buys the prepared material. 

 The most important specifications for oils are the viscosity, measured 

 by the rate of flow, and the unsulphonated residue, or degree of 

 refinement. For dormant spraying the oil should have a viscosity of 

 100 to 120 seconds Say bolt, and an unsulphonated residue of 50 to 

 70 percent. For summer spraying under most conditions the vis- 

 cosity of the oil should be 65 to 75 seconds Saybolt, and the unsul- 

 phonated residue should be at least 85 percent. For yellow varieties 

 of apples, such as the Yellow Newtown, the viscosity of the oil should 

 not exceed 55 seconds. When oil emulsion is used with lead arsenate, 

 it should be put into the spray tank first, and the lead arsenate added 

 just before the tank is full. Combinations of some brands of oil 

 emulsion and lead arsenate may cause a slight burning of the foliage, 

 or the mixture may flocculate or "curd" in the tank. Either of these 

 may be prevented by putting hydrated lime or spreader containing 

 lime into the tank, in the proportion of % pound to 100 gallons of the 

 spray, before the lead arsenate is added. Combination sprays should 

 be used immediately after being mixed. If they are allowed to stand, 

 they may undergo changes that will reduce their effectiveness or 

 increase the difficulty of removing spray residues. As a rule, miscible 

 oils must be mixed gradually with a small quantity of water before 

 they are added to the tank. The manufacturer's directions for mixing 

 should always be followed. The quantities of concentrated oil emul- 

 sion or miscible oil required to make 100 gallons of diluted spray for 

 various purposes are shown in table 2. 



Table 2. — Dilutions of concentrated oil emulsions or miscible oils required for 



various strengths of spray 





Quantity ' of concentrated oil emulsion or miscible 

 oil required to make 100 gallons of spray 



Oil in concentrate (percent) 



Dormant 



strength 



for leaf 



roller 



Dormant strength 

 for scale, red 

 spider, etc. 



Spring 



strength 



for 



thrips 



Summer 



•strength 



for 



codling 



moth, red 



spider, 



etc. 





7 per- 

 cent oil 



4 per- 

 cent oil 



3 per- 

 cent oil 



2 per- 

 cent oil 



0.8 per- 

 cent oil 



98 



Gallons 

 714 

 7H 

 7H 



m 



mi 



Gallons 



m 



M 



m 

 m 



6 



Gallons 



m 



4 



4M 



Gallons 

 2 

 2\i 



2H 



2% 

 2% 

 3 



Gallons 



95 



7 A 



90 



7 <4 



80-85 



1 



75 



IH 



67 



1J4 







All quantities expressed in nearest eighth of a gallon, 



