522 Appendix. 



the best I have seen is that made by Edwards, nurseryman, of Leeds. 

 The stock should be left in the fumes for one hour, and then the 

 fumigating shed well ventilated from above and allowed to clear itself 

 of gas for some hours before the stock is removed. 



The figures given here are for dormant nursery stock and for currant 

 and gooseberry bushes in the ground during the winter and for vines. 

 Treatment of large trees out of doors is troublesome and costly, and is not 

 necessary in this country. 



Recently I have found sodium cyanide far better than potassium 

 cyanide, being stronger ; but I have used the same proportions in 

 fumigating apples and pears in winter. Pickering finds it best to use § to 

 J oz. of potassium cyanide to 100 cubic feet or |^ to ^ oz. of the sodium 

 cyanide, and to each ounce of either 1 oz. of sulphuric. 



Uses. 



This gas is deadly to all forms of life. Not only are all the scale 

 insects on fruit trees destroyed by it, but also their eggs, such as those of 

 the mussel scale. Woolly aphis and all plant lice, etc., are killed, and 

 so are the eggs of most insects (with regard to Lackey moth and one or 

 two others we have no definite result, vide body of the work). The 

 Board of Agriculture leaflet is wrong in stating that insects' eggs are 

 not destroyed. It is well known that those of scale insects, aphides, 

 winter moth, etc., are killed if the full strength given above is used. 



Time op Application. 



Before the stock is planted. It is best left a few days so as to get 

 rid of too much moisture, and the rootage should as far as possible be 

 cleaned of earth. For woolly scale insects on currant and gooseberry 

 Lushes in plantations, February is the best month to fumigate. 



Vineries are best treated in the dormant season, and two fumigations 

 will be found better than one very stong one, at two weeks' interval. 



The temperature should not be more than 60° F., nor should the 

 fumigation be carried out in a bright light. 



Other information is given under Mealy Bug in vines (see p. 484). 



BISULPHIDE OF CARBON. 



This fumigant is little used for nursery stock. It is, however, of 

 some benefit as a soil fumigant. The vapour coming from it being 

 heavier than air, sinks into the soil and is fatal to all forms of insect life 

 it comes in contact with. 



Its eff'ect in different soils and at different degrees of liumidity is very 

 varied, however. 



