BLACK CURRANT EELWORM. 



By Miss A. M. TAYLOR 



{Plant Breeding Institute, School of Agriculture, Cambridge). 



A DISEASE, which is due to a hitherto unrecorded attack of eelworm, 

 has been found causing a considerable amount of damage to black 

 currant plantations in the vicinity of Cambridge. 



There is evidence that the parasite has been established for some 

 years, but owing to its close association with the black currant mite, 

 Eriojjhyes ribis, it has hitherto escaped attention. 



The symptoms produced by the two diseases are similar in many 

 respects and the economic importance of the nematode was therefore 

 not suspected until microscopic inspection constantly revealed the 

 presence of the worm living in unison with the acarid parasite. 



It is evident, now that the life history of the worm has been dis- 

 sociated from that of the mite, that it is responsible for at least an equal 

 share of the damage attributed to that parasite. 



In order that the essential differences between the two pests may 

 be recognised, the following brief outline of similar and contrasting 

 features in the life history of each is given. 



Points of similarity. Both parasites are true ecto-parasites, and 

 both are concerned with the ultimate destruction of the bud. Both 

 are therefore controlled by the same factors, i.e. the seasonal routine 

 of the tree in the production of buds and their subsequent development 

 into shoots. 



Thus there is a period in the life history of both pests when a 

 nomadic existence is led between the young folded leaves, while the 

 buds are in a rudimentary condition — following which is the longer 

 period spent within th^ developing and mature buds. 



Both gain entrance to the buds between the scale leaves from which 

 they pass on to the true leaves. 



