54 DISEASES OF ECONOMIC PLANTS 



yet so much that all the surface is coated, is the aim. This 

 necessitates a good nozzle giving a spray, or mist, and not 

 drops. It implies also intelligent care and close attention 

 to all the details of the operation. 



SOIL DISINFECTION 



Soil disinfection in the field has as yet in the main 

 proved impracticable. All promising chemicals have been 

 tried without avail. Electricity has not given beneficial 

 results, and at present there is no hope of any practicable 

 manner of ridding fields of parasites by any process of 

 disinfection. In a few instances large applications of hme, 

 formalin, or sulphur have proved beneficial (see sweet 

 potato, onion, etc.), but the general practicability of such 

 usage is doubtful. 



Disinfection of limited areas is, however, practicable, 

 is largely employed, and has already resulted in great 

 benefit. Cutting benches, flats, and other benches in the 

 greenhouse, cold frames, and seed beds, and other small 

 areas may be disinfected with advantage. The means to 

 be employed depend upon the area, its location, and the 

 facihties at hand. The leading methods are given below : — 



Baking. — • Flats, pots, and other small containers of 

 earth may often be satisfactorily disinfected by placing 

 them for some time upon the boiler or over a stove, or in 

 an oven for a comparatively long period. 



Permanent steam disinfectors.^ — A system of 1^- 

 inch pipes, which are perforated with ^-inch holes on their 



1 Adapted from Gilbert, W. W., U. S. Dept. Agr. Bur. Plant Indus. 

 Bui. 158, October, 1909. 



