lOTH June, 191 -■] Fumigation for the Destruction of Scale Insects. 369 



sheet will float over the tree without danger of being damaged. The sheet 

 should be sufficiently large to allow of a foot or so to lie on the ground 

 all round the tree. Soil is then thrown over this to prevent the escape 

 of gas, except a few feet, which is left for the purpose of placing in the 

 ■charge. 



When branches of the tree lie on the ground, care must be taken not 

 to cover them up when tucking the sheet around the tree, otherwise, scale 

 occurring on these parts will not be destroyed, owing to the protection 

 afforded by the tent and soil. 



To ascertain the charge required, measure the height and diameter of 

 the tree after the sheet is on. A rod marked plainly off in feet is used 

 for this purpose. 



PLACING SilEEl OVER TRIlL. 



Should the tree be very irregular in shape, it is advisable to take the 

 -diameter two ways, and then take the mean diameter. This also applies 

 in measuring the height. It is usually sufficient to take the extreme height 

 and diameter, but when the margin of safetv is small, as is the case when 

 treating orange trees in the day time, particularly large ones, a good deal 

 must always be left to the judgment of tlie operator. 



After the height and diameter have been taken, a reference to the 

 fumigation table will show the charge required. 



In preparing the charge, the water is first placed in an enamel or 

 earthenware vessel large enough to hold the liquid without danger of 

 boiling over. The sulphuric acid is then slowly added to the water, and 

 the vessel placed w^ell under the tree. When all rs ready, and the tent 

 ■closed down, with the exception of the place where the charge is put in, 

 the cyanide is dropped gently into the vessel. 



