lOTH June, 19 12.] Fu)tiigation for the Destruction of Scale Insects. 371 



180 as given in N'o. 2 table. For example, if a tree is 20 feet high by 

 1 8 feet in diameter, theformulais 18 x 18 x \\ x 20 x ^"^5- x -^\^ = 2 8| nearly. 

 The charge therefore is 28^ ounces of cyanide, 29 ounces of sulphuric 

 .acid, and 87 ounces of water. It will be noticed that i-oz. weights are 

 often required in weighing the cyanide. As these are not always obtainable, 

 a penny can be used, which weighs exactly \ ounce. 



Observation of the result of fumigating trees varying considerably in 

 size, show that small trees are rarely overcharged, whilst with large trees 

 this often happens when the margin of safety is small. Great care, there- 

 fore, must be taken with the measurements in treating large trees, especially 

 •oranges, during the day. 



It has been noted that, when the sheet has been taken off a small tree 

 .after being on for 45 minutes, the odour of the gas has been scarcely 



FUMIGATING FOR RED SCALE MR. RIESCHIECK S PLANTATION, 

 DONCASTER, VICTORIA. 



perceptible ; whereas, in the case of large trees, the odour of the gas 

 was strong. 



The reason of this is that the area of the sheet enveloping a large 

 tree is, in relation to the .space enclosed, less than the' area of the sheet 

 enclosing a small tree. As there is an escape of gas through the undres.sed 

 calico, the wastage of gas is relatively greater in small than in large 

 trees. 



In fumigating deciduous trees during winter for San Jose Scale, a 

 charge one quarter stronger is necessary. This is found by multiplying 

 the quantity of cyanide given in No. i table by 4, and dividing by 3. 

 Sulphuric acid and water are increased proportionately. The cyanide 

 should always be carefully weighed, and the exact charge given. A little 

 more than the prescribed quantity of sulphuric acid can be given withouf 

 harm, and this is done when small fractions are involved. 



Cyanide is a deadly poison, and should be handled with great care. 

 It should be kept in a secure place, and air-tight, when not in use. 

 Sulphuric acid is dangerous also, and care should be taken not to allow it 



