64 



FUMIGATION 



keep below it, i.e., begin to fumigate on the top story and work 

 down, while in the use of bisulfid of carbon the reverse is necessary, 

 and one can work for quite a long period in the fumes of the latter 

 gas until dizziness is felt. 



Fumigation of Greenhouses with Hydrocyanic Acid Gas. 

 Excellent for mealy bugs, white fly, and aphids, but not practical 

 for red spiders and scale insects. 



William Moore, of the Minnesota Station, has done some 

 excellent work in this direction, and we are privileged to quote 

 from his report as well as from results attained by Whitmarsh, 

 of Ohio, and Davis, of Illinois. 



In the fumigation of greenhouses, there are a number of factors 

 to be taken into consideration. The most important feature is to 



FIG. 89. Diagram of greenhouse with two sides of roof equal. 



have the greenhouse accurately measured, so that one can deter- 

 mine the exact dose of chemical which is necessary to kill the insect 

 pests and not destroy the plants. 



Contents of House. Figure 89 shows a view of a greenhouse 

 which has both the slanting roofs equal and the height of each 

 side equal. Such a house is very easily measured and the number 

 of cubic feet determined. In a house of this kind, the height AB 

 is multiplied by the width AE and the result multiplied by the 

 length AH. This gives the number of cubic feet of space in the 

 rectangular portion ABDE-H. The upper portion is still to be 

 estimated. For this purpose, take the height CG and subtract 

 from itAB, the height of the side. This will give the height of the 

 line CF. Multiply CF by the width FB (which equals GA or half 

 AE). This will give the number of square feet in the section BCD. 

 The number of square feet in BCD is multiplied by the length AH, 



