73 



With reference to the different varieties of Black Currant, 

 certain forms have been claimed to be immune, but further 

 evidence is required as to this supposed immunity, which 

 too often breaks down. It is often observed, however, that 

 in a plantation where several varieties are grown some are 

 more subject to attack than others, while occasionally almost 

 free bushes are found in close proximity to plants badly 

 diseased. There is, undoubtedly, much variation in the 

 [lowers of resistance shown both by different varieties and by 

 different individuals in each variety, and the establishment of 

 a- highly resistant race does not seem impossible. 



2. In gardens, attacked buds should be destroyed as soon 

 as they can be detected so 'as to kill the mites before the period 

 of migration. In commercial orchards, if many of the bushes 

 are affected, it may prove impracticable to collect " big buds,'' 

 but when the mite first appears in a previously clean plantation 

 the twigs carrying diseased buds should be removed and burnt. 

 If only one or two bushes show signs of attack it is better 

 to remove and burn the whole bush. It might be thought 

 that in the case of a bad attack cutting the bushes to the 

 ground would prove a complete cure, but this has not proved 

 to be the case, though it is not known how the fresh shoots 

 become infested. Success has been claimed, however, for 

 certain systems which are based on drastic pruning of thi? 

 nature. The bushes are planted much more closely than usual, 

 and then either (1) every alternate bush is annually cut to the 

 ground or (2) the whole of the old wood is removed immediately 

 after the fruit has been gathered. 



3. Some growers appear to have obtained considerable suc- 

 cess by applying dry or wet " sprays," while others have 

 reported a complete failure. Treatments of this nature are 

 open to the objection that the mites are only affected by them 

 when on migration, and, as the migratory period extends over 

 three months, it is necessary to spray or dust several times. 



The dry spray treatment, originally suggested by Collinge,* 

 is, perhaps, in more general use than the wet spray. It con- 

 sists in dusting the bushes four times with ground quick lime 

 and sulphur, at intervals of a fortnight, beginning at the 

 end of March. The first dressing should contain only 1 part 

 of quick lime and 4 parts of sulphur, the second!, 1 part of quick 

 lime and 8 parts of sulphur, and the last two dressings, sulphur 

 alone. Eisk of burning is lessened by using slaked lime 

 instead of quick lime, about equal quantities of lime and 

 sulphur being allowed. The powder should be applied when 

 the bushes are damp, and it is best distributed by means of 

 one of the machines made for the purpose. 



* Collinge, " A Marraal of Injurious Insects, pf . 240, 241. 



