68o 



Gooseberry Black-Knot. 



[FEB., 



3. Infested bulbs may be fumigated with bisulphide of 

 carbon. The bulbs to be treated should be placed in an 

 air-tight receptacle, and a saucer, containing the bisulphide 

 of carbon should then be placed on the top of them, and the 

 receptacle closed. The bulbs should be left in the vapour 

 for forty-eight hours. This treatment could be usefully 

 extended to imported bulbs, which ought to be examined 

 for the mite. The formula for fumigation on a larger 

 scale is one pint of bisulphide of carbon to 1,000 cubic feet 

 of space. Bisulphide of carbon fumes are very poisonous, 

 and should not be breathed, and no naked light (the operator, 

 for example, should not be smoking) must be brought near them. 



A revised Leaflet (No. 136) on this pest has now been issued, 

 and may be obtained free of all charge on application to the 

 Secretary, Board of Agriculture and Fisheries, 4, Whitehall- 

 place, S.W. 



The fungus (Plowrightia ribesia, Sacc.) causing this disease 

 is closely related to Plowrightia morbosa, Sacc, the widely 

 distributed " black-knot " of plum and 



Gooseberry Black- cherry trees in the United States and 

 Knot. Canada. 



P. ribesia attacks the stem and larger 

 branches of the gooseberry and of the red and black currant 

 bushes in this country, and it is not uncommon to find the 

 disease in neglected gardens, more especially where currant 

 scale or aphides are present in quantity. The fungus is a 

 wound-parasite, since spores placed on an unbroken surface 

 produce no result, whereas infection follows when spores are 

 placed in a, minute wound in the bark. It seems probable 

 that aphides or scale enable the fungus to gain an entrance 

 to the living tissues of the plant, as happens in the case of 

 larch canker, apple-tree canker, &c. 



The first indication of disease is the wilting and yellowing 

 of the leaves, which fall quite early in the season. As a rule, 

 a branch is not killed outright in the first season of the attack, 

 but during the second year the leaf -buds remain in a half- 

 opened condition and the branch dies, owing to the presence 

 of the fungus mycelium in the conducting vessels, which 

 prevents the ascent of water in the branch. 



