FUMIGATION. 167 



Nursery Fumigation Chambers, — The example set by the curator of 

 the Grahamstown Gardens, and by Mr. Henry Meyers, of the Fernwood 

 nurseries, Newlands, in providing facilities for the fumigation of 

 nursery stock — to which allusion with illustrations was made in last 

 year's report — has been followed by Mr. H. E. V. Pickstone, of Groot 

 Drakenstein, Messrs. Gowie Brothers, of Grahamstown, and by the 

 curator of the GraafF-Reinet Gardens. The two latter nurserymen 

 have erected brick vaults very similar to the one at the Grahamstown 

 Gardens. Other nurserymen have promised to have chambers ready 

 for use at the commeucement of the selling season. All our nursery- 

 men should be provided with fumigation chambers, not only for the 

 treatment of stock being despatched to their customers, but that they 

 may ensure the destruction of any scale insects which might infest stock 

 received by themselves, either from abroad or from other South 

 African nurseries, and also for the disinfection of scions and cuttings. 

 If root cuttings of apple were fumigated before being grafted upon, 

 many of our nurserymen AVould be spared much of the annoyance 

 caused them by the woolly aphis. 



Experiments to ascertai?i amount of Cyanide required. — There is 

 room for considerable investigation in ascertaining the amount of 

 cyanide to a given space necessary to generate sufficient gas to destroy 

 different insects exposed in an air-tight chamber such as nurserymen 

 would use, and if an opportunity presents itself, a little work along the 

 suggested line will be conducted during the present year. A few ex- 

 periments performed last year brought out some interesting facts. In 

 an approximately air-tight closet, the gas from one ounce of cyanide to 

 750 cubic feet in two hours failed to appreciably affect adult scale 

 insects, but destroyed fully 95 per cent, of woolly aphis on stems of 

 apple. One ounce to 450 cubic feet for one hour appeared to be fatal to 

 the red scale in all stages and to all but the eggs of the oleander scale 

 {Aspidiotus nerii), white peach scale (Diaspis amygdall) and greedy 

 scale (Aspidiotus camellia'). The same strength for two hours did 

 little more. One ounce to 300 cubic feet for one hour proved fatal to 

 all stages of the species named and to the eggs of an oleander-infesting 

 mealy bug {Daclylopius sp.), but a few of the adult mealy bugs sur- 

 vived an hour's exposure in one ounce to 200. When any of the species 

 used in the experiments was much massed on the infested surface, the 

 destruction was strikingly less thorough than when the sales occurred 

 singly. A few adult females of the greedy scale in a mass of their kind 

 on the fruit of a large-fruited 8olanum (^Solatium aculeastrum) failed to 

 succumb when exposed for an hour in one ounce to 301), while not one 

 among many hundreds of scattered individuals lived through an hour of 

 of one ounce to 450. Similarly some larviB of the oleander scale shel- 

 tered in the scurf of old scales of its species on American aloe {Agave 

 americana') survived one in 300. These observations confirm what has 

 been suspected with respect to orchard fumigation, that a dose fatal 

 to every scale insect on moderately-infested trees sometimes proves 



