8o 



The Hop Aphis. 



of quassia chips, the bitter principle of which is either directly 

 poisonous to the aphis or renders the leaves distasteful to those 

 which escape. Paraffin reduced to a fine emulsion in the soft 

 soap mixture is also employed ; though extremely effective, 

 killing the aphis at once, it requires to be used with great care. 

 However carefully the emulsion is prepared, the paraffin has a 

 tendency to separate and collect in sensible drops, which scorch 

 any foliage on which they fall. Mr. Cousins, late of the Wye 

 College, overcame this difficulty by dissolving naphthalene in 

 the paraffin, thus rendering it heavier and diminishing the 

 tendency to separate. There are also other patented prepara- 

 tions, but the majority of growers still use quassia and soft soap. 



The soft soap should be carefully selected ; it should be 

 newly-made, and from such kinds of oil as do not yield hard 

 flocks of curd when the soap is mixed with hard water. It is 

 advisable to test beforehand the lathering powers and the 

 character of the curd that is formed by dissolving i oz. of the 

 soap in question in half a gallon of water, shaking well, and 

 observing the stability of the latter, and whether any curd 

 separates on standing. The amount of soap to be employed 

 varies with the hardness of the water ; with soft water 4 lb. per 

 IOO gallons will be sufficient, while hard waters often require 

 8 or 10. Large quantities of soft soap will scorch tender 

 foliage ; hence when the water is hard it is advisable to have 

 an analysis made, as it is often possible to reduce the hardness 

 by adding a little carbonate of soda. 



Six pounds of good quassia chips are simmered for two hours, 

 with just enough water to keep the mass liquid ; the decoction 

 is strained off, and the soft soap is stirred in till it dissolves, a 

 process which may be assisted by further boiling. This stock 

 mixture is diluted down as required with cold water to 100 

 gallons. 



Many forms of spraying machines are used for distributing the 

 wash. For small gardens, a hand machine with two nozzles on 

 flexible tubes is used, but large acreages require the use of horse 

 machines holding about 80 gallons of wash, the double or triple- 

 acting pump being driven from the wheels of the machine as it 

 moves along. From an account of competitive trials of various 

 machines, the Journal of the Royal Agricultural Society for 1899, 



