Fumigation by Hydrocvanic Acid Gas. [sept., 



packed, dark coloured conidiophores, each bearing a dark, many- 

 celled conidium at its tip. 



Preventive Means. — Thorough spraying with potassium sul- 

 phide solution at frequent intervals. All diseased parts should 

 be cleared away and burned, otherwise they continue to grow on 

 shrivelled fruit, stems, and leaves. The use of stable manure is 

 considered to favour the disease, and also causes the fruit to 

 crack, thus rendering it susceptible to a high degree. 



Fumigation by Hydrocyanic Acid Gas is recommended as a 



remedy for mussel scale (Leaflet No. 107), and also in the case 



of young nursery stock for the prevention 



Fumigration by Woolly Aphis and other pests. It is also a 

 HydFOcyanie - , r 1 • 1 u 



Acid Gas.* "^^^^ useful means 01 clearmg glass-houses 



of insect pests, mealy bug on vines, &c. 



In leaflet No. 107 a treatment suitable for young fruit bushes 

 or trees is described. The following instructions are more 

 applicable to greenhouses, conservatories, &c. : — 

 • The materials necessary for purposes of fumigation are : — (i) 

 cyanide of potassium ; (2) sulphuric acid ; and (3) water. 



The proportions in which these are used and the amount of 

 space per unit of cyanide vary slightly as recommended by 

 different workers, thus one recommends : — i oz. of cyanide 98 

 per cent, purity to every 500 cubic feet of space ; another, i oz. 

 of cyanide 98 per cent, purity to every 300 cubic feet of space ; 

 and another, i oz. of cyanide 98 per cent, purity to every 200 

 cubic feet of space. 



Strawson recommends the following as a standard : — Half as 

 much again of sulphuric acid as cyanide, and of water 2\ times 

 more than the quantity of acid, thus : — Cyanide of potassium, 

 98 per cent., i oz., sulphuric acid \\ fluid oz., and water 4 oz. 



The variation in the amount of cyanide depends to some 

 extent on the character of the plants that are being treated. 

 In the case of tender plants, i oz. of cyanide may serve for 500 

 cubic feet of space, while hardy plants may be treated with 

 I oz. of cyanide to 200 cubic feet of space. 



Method of Application. — The glass-house or other place which 

 is to be treated must be rendered airtight. 



* [ournil, Vol. XII., p. 496, Nov., 1905. 



