900 



Hop Cultivation. 



[FEB., 



prefer to see a few leaves knocked off by the force of the wash 

 as an indication that there is plenty of force and that the 

 aphides are receiving a good drenching. 



When to Wash. — This is one of the most difficult of the 

 problems which the hop-grower has to face, for there ate 

 many conflicting circumstances that have to be taken into 

 account. 



The aphides begin to arrive about the beginning of May 

 and sometimes continue until the end of July, though usually 

 the last batches come about the middle of that month. It is 

 therefore useless to exterminate the early arrivals if the later 

 ones are left to thrive. On the other hand, the aphides must 

 never be allowed to accumulate thickly enough upon the 

 leaves to check in any way the growth of the plant. Again, 

 the hop-grower is assisted by one natural enemy of the aphis, 

 the ladybird and its larva?, which in favourable seasons 

 (e.g., 1908) are sufficient by themselves to keep the aphis in 

 check for a considerable time and so save the grower the 

 expense of washing. Unfortunately, washing kills both 

 ladybird and aphis ; nevertheless, washing must never be 

 delayed on this account, and, if there is any danger of the 

 aphis checking the plant, washing must be done at once. 

 Further, it must be remembered that the aphis can be much 

 more effectually killed whilst the foliage is thin ; when growth 

 becomes dense the leaves shelter each other from the wash, 

 and so the aphides escape. Finally, when the young hops 

 begin to form and the aphides get into these, washing can do 

 but little good. 



The plan of the hop-grower should be to keep the insects 

 well in check during the earlier part of the season, and when 

 July comes and the winged aphides begin to cease coming he 

 should concentrate all his efforts to clean his hops before 

 the hop cones form. Lastly, it is most important that the 

 late hops (the last pickings) shall be clean, because whilst it 

 is sometimes possible to gather the earlies before these are 

 quite ripe if the aphides become dangerous, this is not 

 possible in the case of the late hops. 



Types of Washing Machines. — Mop washing machines 

 may be divided into three classes according to the power used 

 to produce the force. 



(i.) Hand Washing Machines. — A hand washing machine 



