56 METHODS OF PREVENTION AND REMEDIES. 



ascertained this fact by experience, the foreman in 

 charge of the Board's outfit refrained from covering 

 trees until the sun had sunk from sight on any but 

 cool dull days. The great majority of the trees treated 

 have been fumigated after sunset. The ideal night 

 for fumigating is quiet, cool, and moonlight, and 

 without dew." 



From such valuable and trustworthy evidence ,i> 

 the foregoing we may safely take action with con- 

 signments of hard- wooded plants. But for such tender 

 things as orchids or other rare and costly plants 

 the process is likely to end in serious injury to them, 

 and cannot therefore be expected to find universal 

 favour amongst English horticulturists.* There is this 

 to be added, however, that all other fumigating com- 

 pounds have been found by Mr. Green less effectual 

 to Coccids and more injurious to plant life than the 

 hydrocyanic acid gas. 



In the absence of fumigation or of the application <>\* 

 insecticides, which, owing to the nature and condition 

 of the plant, may be deemed inadvisable, a thorough 

 sponging with clean water should invariably be made. 

 All foreign substances should be removed, and the 

 plant or plants afterwards watched for any signs of the 

 development of scale or bug. 



Coccids are also freely imported into this country on 

 oranges and lemons, including the troublesome and 



* In the Journal of the South-Eastern Agricultural College, Wye, 

 Kent, No. 9, April, 1900, Mr. H. H. Cousins gives ;i report on some 

 excellent results obtained by fumigation of vines and greenhouse 

 plants with hydrocyanic acid. For inealy bug he recommends " 3| oz. 

 cyanide, 5 oz. acid, 8 oz. water per 1000 cubic feet, either before the 

 vines bloom, or when grapes are colouring, or after the crop has been 

 gathered. At either of these stages no harm results to either foliage 

 or fruit. Avoid fumigation when the vines are in bloom or before the 

 grapes have commenced to ripen," (1. c., p. 70). 



" For ordinary greenhouse pests, such as aphis, dolphin, white-fly, 

 slugs, woodlice, red spider, and caterpillars, a dose not exceeding If to 

 2 oz. cyanide, 4 oz. acid, 7 oz. water per 1000 cubic feet has proved 

 itself satisfactory," (1. c., p. 70). In one greenhouse in which the 

 experiment was conducted there were chrysanthemums in full bloom. 

 Mr. Cousins says " not a petal or leaf was injured." 



