RECENT WORK WITH HYDROCYANIC ACID GAS 203 



from without. The foliage of the plants should be 

 dry. A temperature not exceeding 60 F. and prefer- 

 ably of 50 F. is desirable. Above 60 F. there is 

 risk of injury to the foliage. 



For mealy bug, 3 ounces cyanide, 5 ounces acid, 

 15 ounces water per 1,000 cubic feet, either before the 

 vines bloom, or when grapes are coloring, or after the 

 crop has been gathered. At either of these stages no 

 harm results to either foliage or fruit. Avoid fumi- 

 gation when the vines are in bloom, or before the 

 grapes have commenced to ripen. 



For ordinary greenhouse pests, such as aphis, 

 dolphin, whitefly, slugs, woodlice, red-spider, and 

 caterpillars, a dose not exceeding 1 24 to 2 ounces cya- 

 nide, 4 ounces acid, 7 ounces water per 1,000 cubic 

 feet, has been found satisfactory in England. For a 

 detailed, account of greenhouse fumigation see Chap- 

 ter XIV. 



Use in New South Wales. In the center of the 

 citrus-growing belt of New South Wales, W. J. Allen, 

 an expert of the government, has conducted some very 

 satisfactory experiments with hydrocyanic acid gas in 

 cooperation with the Glenorie Progress Association. 

 Various sprays were tried at the same time and com- 

 pared with the gas treatment. In his report of the 

 practical tests, printed in Vol. XII. of the Agri- 

 cultural Gazette of New South Wales (see also Agri- 

 cultural Gazette for August, 1899, an ^ July, 1900), Mr. 

 Allen says: 



The fumigation of the trees with hydrocyanic acid 

 gas gave the best results of all. This was conceded 



