1 



THE JOURNAL 



OF THE 



BOARD OF AGRICULTURE. 



THE INSECT AND ALLIED PESTS OF THE HOP 



(Continued.) 

 Fred V. Theobald, M.A. 



South-Eastern Agricultttral College, Wye. 



The Hop Aphis. 

 (Phorodon humuli, Schnk.) 



The Aphis, or "Fly," is by far the most general and 

 persistent enemy of hops in all parts of the world where they 

 are grown. Every year it is present to a greater or less 

 extent; every locality is liable to its invasion, and every 

 variety of hop is subject to the depredations of this small 

 insect. So persistent is the attack of Aphis in some years 

 that as many as seventeen washings have been given before 

 the pest was conquered. In 1882 the damage done by the 

 Aphis was said to amount to ;£ 1,750,000 and over ,£200,000 

 was spent in labour. 



The life-cycle of the Hop Aphis was first traced by Dr. 

 Plomley in 1849 in the Maidstone area, and was afterwards 

 followed by Riley, the American entomologist, and others. 

 Koch in 1854 records the Hop Aphis on Plum and Sloe, and 

 says: "In June this Aphis quits the leaves of the Sloe, and 

 then betakes itself to tHe wild and cultivated hop." Two other 

 German authors — Taschenberg and Kaltenbach — in 1880 and 

 1874, a lso refer to it as coming from Prunes. At present we are 

 still unable to account for all the vagaries of this "dolphin," 

 and there are evidently important features in its biology 



Vol. XVI. No. 8. 



NOVEMBER, 1909. 



The first part of this article, with Plates I., II. and III., appeared in the journal, 

 October, 1909, p. 555. 



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