Fifty Years of Hop Farming. 
333 
increase of damson trees in the hop-growing districts has caused 
the attacks of aphides to be more frequent and persistent. 
For clearing the hop plants of aphides, hop-washing engines, 
which are enlarged garden engines with strong pumps, are used. 
These have a length of hose on either side fitted with spray jets, 
which are directed upon the hop plants by two men, while 
another man works at the pump. 
On large plantations, washing-machines, as shown by Fig. 
5 below, are drawn by horses between the rows of hop plants ; 
Fig. 5. — A Horse Hop-washing Machine. 
these are fitted with rows of pipes perforated at proper intervals, 
which can be so adjusted that in all stages of growth the wash 
is forced by the pumps evenly over the plants. 
Various washes are employed. Nothing has been found to 
be more efficacious than the extract of from seven to nine pounds 
of quassia chips with six to eight pounds of soft soap to 100 
gallons of water. 
Washing is a costly and tiresome process, since it is impera- 
tive that each leaf must be treated, as if only two or three 
