252 Blacli Currant Eelworm 



free bud. It is probable, however, that under orchard conditions, 

 decay would take place more rapidly, for the number of worms with 

 which the buds were inoculated in the laboratory, was necessarily 

 small. 



It is obvious that the continuous destruction of the buds influences 

 the growth of the tree. Especially is this the case during the spring 

 and early summer when new growth is being actively made. If, 

 for example, a shoot known to be infected with w^orms is kept under 

 observation in the spring, it is seen that the wood buds which have 

 escaped attack will push into growth. These shoots, proceeding as 

 they do from centres of infection, may grow a few inches and then 

 suddenly wilt and die, owing to the worms piercing the delicate tissues 

 of the young stem and destroying the developing leaves. The con- 

 centration of the sap in the unattacked buds below such an abortive 

 shoot usually causes several of the nearest unattacked buds on the 

 old wood to break into shoots. These may, if growth is being rapidly 

 made, attain to the length of from six inches to a foot. Upon exami- 

 nation of the minute buds they bear it will be found that few have 

 escaped attack. The following figures were taken from such shoots 

 in the first week in April: 



Shoot of 30 buds shewed 28 killed with 2 expanding normally. 



The terminal buds on such infected shoots are invariably killed, 

 as are many of those immediately below. If all the buds at the apex 

 of those new shoots are successively attacked (and such is a frequent 

 occurrence) the shoot dies back to the nearest unattacked bud. The 

 new basal wood which considerably influences the yield of fruit in 

 black currants, is similarly attacked and destroyed. 



Repeated efforts are thus being made by the tree during the growing 

 season to produce new wood with the result that an irregular growth 

 of twigs is produced about a diseased area. During the resting season 

 no alteration takes place in the growth of the tree, but the worms 

 continue to destroy the buds. In the spring long lines of unexpanding 

 buds, interspersed with a few which are developing normally, shew 

 the effect of the activity of the worms during the months when the 

 trees remain dormant. Such a condition is shewn in the accompanying 

 text figure. 



