APPLE POWDERY MILDEW AND ITS CONTROL. 21 
PREPARATION OF CRUDE-OIL EMULSION. 
Crude-oil emulsion, ready for applying, is prepared as follows: 
Vat eI eer et Ep ee pep eR te Ba od ee 175 gallons. 
AMS Ta UNS Ae a sa ae ge eg 10 to 12 pounds. 
bye Ccaustic soda) <_-=.- 23 22 22 == ete PI a No 2 pounds. 
California cruderoil= vers. so sR hs te ee ae Se nae 25 gallons. 
The materials are to be mixed in the spray tank in the order given 
and with the agitator in motion. The fish-oil soap should be dis- 
solved in hot water before adding it to the 175 gallons of water in 
the tank, and for the first trial 10 pounds should be used. The re- 
quired weight of lye may be added directly to the soap solution in 
the tank, allowing a few minutes for it to dissolve before pouring 
in the 25 gallons of crude oil. A light-brown emulsion should be 
formed as soon as the crude oil is added, and none of the oil should 
remain floating on the top of the mixture. Very little agitation is 
required to keep the oil emulsified, and the mixture is ready for 
immediate use. If the crude oil does not emulsify properly—that 1s, 
if some of the oil floats on the surface or if the mixture seems to 
contain small globules of oil—the preparation has not been successful. 
The trouble may be due to a lack of sufficient soap, in which case 
the remaining 2 pounds should be dissolved in hot water and poured 
into the tank. In some cases, when very hard water is used, a little 
extra lye may be required, and in rare cases it is necessary to use less 
than the 2 pounds. Occasionally a little difficulty 1s experienced in 
preparing the first tank of spray, but when the proportions of soap 
and lye are once determined there will be no trouble in making the 
emulsion. 
It will be noted that the above formula gives a 124 per cent crude- 
oil emulsion. Such a mixture must be used only when the trees are 
entirely dormant, preferably during January. The spraying should 
be very thoroughly done, so as to produce a uniform, shiny, dark- 
brown coating over the entire surface of the twigs and branches. 
It may be well to repeat the statement that this winter spraying 
with crude-oil emulsion is not for the direct purpose of controlling 
the mildew, but is intended as a stimulant which will induce the 
production of vigorous early foliage, and this latter is of decided 
importance in mildew control. 
Investigations that are still in progress seem to indicate that 
under some conditions dormant spraying with solutions of nitrate of 
soda plus caustic soda will be more desirable than crude-oil spraying.! 
1 Ballard, W. S., and Volck, W. H. Winter spraying with solutions of nitrate of soda. 
Journal of Agricultural Research, v. 1, ne. 5, p. 487-444, pl. 50-51. 1914, 
