The Hop Aphis. 287 



sistency. We found it best not to make more of the tobacco decoction tlian could 

 be used up in two days, because if tlie material was kept longer it fermented. 

 The decoction then was not so effective an insecticide as when fresh, probably 

 because of a breaking-down of the nicotine products under the action of fermen- 

 tation. The kerosene emulsion also should not be kept too long before using, 

 because of a tendency which even the most carefully made emulsions have to 

 separate and allow free oil to appear. 



The spray material was made up by taking forty gallons of the tobacco 

 decoction and to it adding three and one-half gallons of the emulsion. This was 

 stirred frequently while being applied to the vines, so that tlie mixture was of 

 uniform quality. \Ye found that a certain amount of separation of the oil in the 

 spray tank was unavoidable in practice. To avoid placing this upon the vines, 

 it is best not to use for spraying the last two or three inches of material from 

 the tank. The free oil burns the hop foliage badly, hence this residue should 

 be emptied out before refilling the tank. 



We used in this yard an outfit consisting of a fifty-gallon barrel and a good 

 spray pump set up on a sled. This, when loaded, was not too heavy for one 

 horse to haul quite readily. Two fifty-two foot leads of hose and short rods were 

 found to economize labor to the best advantage, the sprayers working away from 

 the outfit and covering five rows on each side of the one through which the horse 

 was driven. Vermorel (eddy-chamber) nozzles were used in this work, and great 

 care was taken to get the spray material on the under sides of the leaves, where 

 most of the aphids are found. This one outfit, employing one man to drive and 

 pump and two men spraying, covered from three and one-half to four acres a day. 

 We found it necessary to go over the yard three times before the hops were ready 

 to pick, and we averaged for these three sprayings sixty gallons of material to the 

 acre for each application, or for the entire work one hundred and eighty gallons 

 to the acre. To economize labor, enough of the material to last a half day was 

 made up in the morning- and again at noon : and this was hauled out to the 

 hop yard and left in a situation that would enable the men who were employed 

 in spraying to fill up the barrel on the sled with the least possible delay. We 

 found this to be a great economizer of time and expense. 



The cost of the materials used was as follows : Kerosene, 24 cents per 

 gallon ; soap. 5 cents per pound ; tobacco waste. 1 1-2 cents per pound. Labor was 

 worth .'};i.2.'') a day, and the horse 50 cents a day. losing these figures as a basis, 

 we find that each of the three sprayings on this place cost less than .$2 an acre, 

 or for the entire season's work on the fifty acres, about if24f). 



The results obtained by this spraying amply justify the expeud'ture involved. 

 The material used was effective upon the aphids, and when the crop on this' 

 yard was gathered it was uninjured, while untreated vines and yards in the neigh- 

 borhood had the value of their product, both 1n quantity and quality, reduced 

 fully one-half. 



Whale-Oil Soap and Quassia. — The other hop yard in which experimental and 

 control work was done is six miles from Watsonville, and covered nearly one 

 hundred acres. The aphids did not spread over all this yard, and it was necessary 

 to spray only some fifteen acres of it. Work was begun in the last week of June, 

 as by that time the presence of the aphids was quite evident. The spray material 

 used was made up of the extract of quassia chips and whale-oil soap. The quassia 

 extract was made by soaking the chips in water for a day or two and tlien 

 boiling thoroughly for two hours. Seven pounds of the chips were thus treated 

 in three gallons of water, and the extract obtained was poured into two hundred 

 and fifty gallons of water in which nine pounds of whale-oil soap had been 

 dissolved. This was sprayed upon the vines, the outfit used and the method of 

 application being about the same as that previously described. The same amount 

 of material per acre was used in spraying this yard as in the other case ; that is, 

 sixty gallons for each spraying, or a total of one hundred and eighty gallons 

 for the season's work. 



The cost of the materials used was as follows : Quassia chips. 10 cents per 



