620 The Insect and Allied Pests of the Hop. [nov., 



amount of Aphis on the hops. That a very large percentage 

 come from the damson and the plum is now a well-established 

 fact. If the Aphis on the prunes were destroyed, much of 

 the hop blight would be prevented. This can be done, but it 

 is no use unless it is done by all in a district, for Aphis can 

 migrate for some distance. If damson and plum trees are 

 sprayed with lime and salt wash in February or early March, 

 much of the Aphis is prevented from hatching, and any that 

 may have appeared are killed. If this has not been done, 

 an early heavy spraying with paraffin emulsion will kill the 

 mother-queens before they produce their young. This spray 

 should not be used until the blossom is well set. Treatment 

 by washing hops is well known to everyone in general prin- 

 ciple. Either quassia and soft soap or nicotine and soft soap 

 are the best remedies, for they in no way harm the foliage. 

 Nicotine has far greater penetrating powers than any other 

 substance used, and its effects are much more lasting. Many 

 patent washes are employed, some with success, others not. 



The main thing to aim at is to hit every part of the plant. 

 The idea of using a fine mist is a fatal error ; the finer the 

 mist the less likely are the particles to run into drops and 

 so penetrate the small folded top leaves, which one seldom 

 sees cleaned when a fine spray is sent out. Repeated observa- 

 tion has shown that this is where the lice survive and so 

 carry on the attack — not on the large lower leaves, as seen 

 in the photograph. Nothing but a thorough drenching will 

 get at these, and one good drenching will do more good 

 than a dozen fine sprayings. Owing to frequent migrations 

 in certain years, several sprayings may be necessary. It 

 is advisable to have the lower leaves stripped where the hops 

 are washed by horse machines, as the under surface of many 

 leaves is not hit at all. This is not necessary where the spray- 

 ing is done by hand. The work can be far more thoroughly 

 done in the latter way than by horse power. Hand-spraying 

 may be carried out by means of knapsacks, but large areas can 

 only be satisfactorily done by means of steam tackle. 



It is most important to attack the Hop Aphis as soon as 

 it appears, for if left for even a couple of weeks under favour- 

 able conditions enormous numbers may be produced, and 

 then much harm is done, and they are more difficult to 



