CHAPTER XIX 

 RECENT WORK WITH HYDROCYANIC ACID GAS 



UCCESSFUL A PPLI CATION IN ENGLAND. The black 

 currant bud-mite and the mealy bug are among 

 th e most dangerous and elusive enemies of 

 the greenhouse and garden in England. So 

 severe have been the losses by the former that the 

 currant industry is in a critical state. One grower is 

 reported as having said recently that his crop had 

 fallen from 1,400 a year to practically nothing on 

 account of the mite. The latter pest is found gener- 

 ally in the vinery. The application of sprays and 

 washes have not been successful in keeping either pest 

 in check. 



In a recent paper by H. H. Cousins, in the Jour- 

 nal of the Agricultural College, at Wye, Kent (Vol. 

 XXV.), he reports successful results where hydro- 

 cyanic acid gas was used. Speaking of his experi- 

 ments, he says the spread of the black currant bud-mite 

 is clearly due in the first place to the propagation by 

 cuttings from infested stock. Buds of apparently 

 normal dimensions frequently contain a few mites 

 capable of indefinite increase. In the case of the 

 Baldwin currant it is most difficult to find a shoot free 

 from mites, even when the buds appear quite healthy. 

 Diseased stock undoubtedly spreads the infection by 

 the mechanical distribution of the mites on the clothes 



iq8 



