238 Insect Pests. 



The wind, the clothes of the men working among diseased bushes 

 and the soil carried away on their boots are certain means. Lady- 

 bird beetles feeding on aphis on the currants carry the acari with 

 them. One of the most prevalent means is distribution by the Eed 

 Bee (Andrena rufa) and the Hive Bee {Apis mdlifica), both of which 

 visit the bushes when in blossom. 



The great cause of the increased area over which the attack has 

 spread is to be looked for in the propagation of diseased cuttings 

 from infested stock. When considering this point, it should be 

 noticed that the old varieties of black currant were rarely, if ever, 

 attacked, and cuttings were seldom taken from them, while one of 

 the commonest varieties, and the one that was very largely propa- 

 gated, namely, the Baldwin, is also the kind that is the worst infested. 

 Owing to the prevalence of disease, growers have given up the 

 Baldwin to some extent for other varieties, such as Black Xaples 

 and Lee's Proliflc, with the result that these are now, in many 

 districts, as much infested as the Baldwin variety. Before the attack 

 was so well known as is the case at the present time, the sending out 

 of diseased stock from nurseries was to a large extent responsible for 

 the spread of infestation. 



Eecords show that cuttings have been taken from infested bushes 

 solely on account of the large size of the buds, which was taken as an 

 indication of extra strength and vigour. 



I am quite sure from some observations made that the mite may 

 be spread, from an infested to a clean plantation, by means of the 

 baskets used in picking the fruit. 



Some of the agents of distribution mentioned above, especially 

 insects, would probably form the natural means whereby the disease 

 is spread, and if this distribution had been dependent on them alone, 

 the disease would not have obtained such a strong hold as is now 

 the case, and would not have spread to anything like its present 

 extent. 



The grower and the nurseryman, however, by means of propaga- 

 tion from diseased stock, have done more to cause the loss which 

 they now experience than all the natural agents put together. The 

 necessity of obtaining clean cuttings in the first place cannot be too 

 strongly insisted upon, and when obtained they should be put out on 

 fresh ground not previously planted with black currants, situated 

 as far away as possible from any infested plantation. It is possible 

 also that birds may help to carry the pest from place to place over 

 wide areas. 



