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



commence to breed in any numbers until June. An attack 

 of Red Spider usually begins on the lower leaves. This 

 species is also found living on the hollyhock and French 

 bean. 



The Red Spider of vines (Tetranychus telarius) is quite 

 distinct from the Red Spider of Hop, being much smaller, 

 as I pointed out in my report of 1903.* 



Prevention and Treatment. — There is no doubt that the 

 red female acari hibernate in crevices, &c, of hop poles, in 

 broken pieces of bine, and in the snags and other places. 

 It is thus essential to see that all woodwork is well 

 cleaned and made as smooth as possible, and that all un- 

 necessary shelter is burnt in winter. The increasing use of 

 wire undoubtedly tends to the decrease of this pest. After 

 an attack it would be well to have all woodwork in wired 

 gardens well drenched with strong paraffin emulsion in 

 winter, or with any patent wash left over from spraying. 



The best wash for Red Spider is liver of sulphur, but liver 

 of sulphur frequently harms the foliage; so also does paraffin 

 emulsion, the other acaricide. One or the other must be 

 used, as no other substance is known to affect these mites. 

 Repeated experiments with all strengths of nicotine have not 

 given a single good result, either on the Bryobia or Tetra- 

 nychus. It is necessary to use force with the wash for this 

 pest, both in the case of liver of sulphur and paraffin, as the 

 wash needs to be driven hard so that it breaks the webbing 

 and penetrates to the acari beneath. It is also necessary to 

 wash twice in succession with an interval of about ten days, 

 as no known acaricide will harm the eggs. 



If there is a combined attack of Aphis and Spider, then 

 nicotine can be mixed with the liver of sulphur. Liver of 

 sulphur may be used up to 2 J lb. to the 100 gallons, but this 

 may affect the leaves under certain conditions, and it is safest 

 not to use more than ij- lb. 



Miss Ormerod records the Red Spider of hops as being 

 destroyed by a small black ladybird beetle known as Scymnus 

 minimus, Rossi. 



* Second Report on Econo?nic Zoology (British Museum, N.H.), p- 142, 1904. 



