CHAPTER XIX 
RECENT WORK WITH HYDROCYANIC ACID GAS 
UCCESSFUL APPLICATION IN ENGLAND.—The black 
currant bud-mite and the mealy bug are among 
the 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 
198 
