1909.] The Insect and Allied Pests of the Hop. 627 



way out through it and the rind and enter the soil, where 

 they are found as minute white worms, which wander about 

 and fertilise the females. 



The entire development takes from four to five weeks, and 

 successive generations occur throughout the year, reproduc- 

 tion going on as late as November in any case. 



Treatment. — The methods of prevention and treatment that 

 suggest themselves from experiment are the following : — (1) 

 The application of lime, for it has been noticed that this and 

 other eelworm attacks are most frequent in soils deficient 

 in lime, and that an application of it to infected soil has 

 proved of benefit; (2) the use of sulphate of potash at the 

 rate of from 2 to 3 cwt. to the acre. This undoubtedly affects 

 the parasites in the soil, not only just around the affected hill, 

 but also around those near it; (3) collection of the parasites 

 by means of "trap" plants. It has been found that winter 

 rape especially, sown thick, soon becomes attacked. The 

 young plants may then be dragged up and destroyed; a 

 second sowing should be made at once and treated in the 

 same way. It appears that buckwheat attracts this eelworm, 

 and it might be tried. This is especially to be recom- 

 mended where a badly diseased hill has been grubbed, for 

 many of the worms will be left with the fine rootlets in the 

 soil, and would spread to neighbouring hills. An interest- 

 ing feature first noticed by Percival is that transplanted hops 

 suffering from Nettle-head show no further signs of the 

 disease. It is possible, therefore, that cutting away the roots 

 or digging up and replanting might be effectual. 



The Stem Eelworm. 

 (Tylenchus devastatrix, Kuhn.) 



Some years ago Prof. Percival * referred to the presence 

 of this common plant parasite in hops. The part it played 

 in connection with Nettle-head was very doubtful, and it 

 may now be said that it has nothing to do with that specific 

 disease. 



This Eelworm nevertheless may frequently be found in the 

 roots of hops that are either unhealthy or dying. In several 

 cases investigated during the last three years I have 



* Journal S.E. Agric. College, No. I. p. 7, 1895. 



