VI. 



An Eelworm Disease of Hops. 



IN September, 1894, Natural Science (vol. v., p. 170) was good 

 enough to draw the attention of its readers to my investigation 

 of a new disease, which causes hops to become what is termed 

 " nettle-headed," and which during the last two or three years has 

 been giving a considerable amount of trouble to growers in several 

 of the hop districts of Kent. 



The following paper is the more extensive communication which 

 was then promised to this Review. Last July I was asked to examine 

 some of the affected plants, and since that date have been busily 

 engaged in investigating the matter. The results of the work are, I 

 venture to think, of the greatest importance, as the disease, if 

 thoroughly established, promises to become one possessing serious 

 consequences to the hop-grower. 



The exact distribution of the disease in the county I have not 

 been able to learn, owing to want of accurate observation and 

 description on the part of the growers, and also to the inherent 

 difficulty of distinguishing the disease in its early stages from obscure 

 pathological conditions induced by unfavourable soil and manures. 

 However, where it has been known for some time it has assumed a 

 more virulent character, with well-marked characteristic symptoms. 

 Affected plants are said to be " nettle-headed," " silly," or " skinkly." 

 Isolated examples seem to have been noticed as long ago as 1880, 

 but these cases did not extend beyond very small areas in the 

 gardens. Lately, however, the disease has spread considerably, and 

 necessitated the complete uprooting and destruction of several acres 

 of plants in various localities. One correspondent informs me that 

 it first appeared in old plantations of " Colegates," and spread to 

 such an extent that this variety has almost gone out of cultivation. 

 Almost all varieties are subject to attack, but there is a general con- 

 sensus of opinion that the early kinds suffer most, and especially 

 on loamy soils. The worst cases are met with in old gardens, and 

 the disease is rarely noticed on a serious scale until five or six years 

 after planting. I have, however, seen plants attacked in the second 

 year, and this may become the rule rather than the exception. 



The parts above ground in a typically diseased specimen show a 

 marked want of vitality, although this stunting of growth is not 



