550 ANNUAL REPORT OF THE Off. Doc. 



FUMIGATION. 



Fumigation has proved absolutely effective in extended tests on 

 stock infected with the San Jo&6 Scale; but in other tests because of 

 impure chemicals, leakages in the fumigating chamber, or the pres- 

 ence of a mud covering over the scale the live scales remained upon 

 the stock. 



The fact that it is easier to combat new insects by prevention than 

 to exterminate them after their establishment, leads careful planters 

 to set out only fumigated stock, for they have an additional safe- 

 guard by so doing. 



For each 100 cubic feet of space use fused cyanide of potassium 

 (98 per cent. pure). One ounce by weight. 



Commercial sulphuric acid one and one-half ounces by measure. 

 Water three ounces by measure. Expose three-fourths of an hour. 



Good fumigation chambers are lathed and plastered with doors 

 made refrigerator style to make the chambers as nearly air-tight 

 as possible. A tight board construction, if doubled with j)aper be- 

 tween, answers well. The stock should rest on a grating or other 

 support to permit free circulation of the gas, and means for ventila- 

 tion after use should be provided. The stock should not be wet 

 nor should mud or earth cover any part liable to infestation. 



The gas should be generated as near the centre of the lot to be 

 treated as practicable, and in case of large amounts, several genera- 

 tors should be used and so placed that rapid and uniform distribu 

 tion of the gas will be insured. The cyanide must be kept in tight 

 bottles in a safe place as it is a volatile, deadly poison. The cubical 

 contents of the fumigating chamber should be estimated, the cyanide 

 weighed out in amounts sufficient for a treatment and put in paper 

 bags. Pour the acid slowly into the water, stirring the mixture con- 

 stantly, otherwise drops may fly and burn those in the vicinity. 

 After the stock is properly arranged, pour the necessary amount of 

 diluted acid into a glazed earthen vessel, place the cyanide while 

 still in the paper bag into th6 acid and water and close the fumiga- 

 tor. The advantage of putting the cyanide into the acid and water 

 while still in the paper bag is that it prevents sputtering which is 

 specially liable to occur when large amounts are used. Great care 

 should be exercised in handling the cyanide, the acid, and in opening 

 after fumigation. The substances used are deadly; even a slight 

 burn from sulphuric acid is very painful. 



Bordeaux Mixture — Copper sulpliate (blue vitriol), ^ pounds; 

 quick lime (best stone lime), 5 pounds; water, 50 gallons. 



Dissolve the copper sulphate quickly by suspending it in n bag in 

 and near the surface of about six gallons of water. Slack the lime 

 using only the amount of water necessary to keep i1 covered and 



