Aug. 15, 1925 
Soil Disinfection for Potato Wart 
319 
cost of a trained supervisor. The foregoing costs assume that the 
laborers could do all razing and replacing of fences and poles and all 
treatments of soil that could not be treated by the steam pan. In 
this work a 5 by 9 foot and a 6 by 9 foot steam pan were used, which 
weighed about 400 pounds each; but with several strong men or 
special devices, larger ones could be used. Treatment would obvi¬ 
ously be so slow that several outfits could probably be used to advan¬ 
tage, greatly reducing the cost of transportation of labor and coal and 
possibly enabling a small crew to handle all labor for several outfits. 
It seems doubtful if the cost could be reduced much, if any, below 
$1,500 per acre. 
Cost of Chemical Treatments 
The applications of chemicals made in 1921 were extremely heavy, 
and it seems probable that positive results have been obtained with 
such of these chemicals as are capable of effective sterilization. The 
quantity of chemical used for some of the treatments could doubtless 
be reduced considerably without loss of efficiency. It has not been 
possible to carry out experiments to determine the most effective 
and economic quantity of each chemical used. None of the treat¬ 
ments have been tried on a sufficiently large scale to make possible 
the giving of estimates of the cost per acre of application of the 
materials listed. The steam used in the steam-pan experiments 
was furnished free of charge by a local coal company. Treatments 
requiring water would be relatively expensive to apply since there 
would be large quantities of solution to handle, and water solutions 
soak into the ground more or less slowly. In much of the region 
where potato wart occurs, the water supply is inadequate during most 
of the growing season and special reservoirs would have to be con¬ 
structed to retain the spring run-off if water solutions were to be 
used on a large scale. Experiments have shown that Bordeaux 
mixture will penetrate the soil hardly at all and must be worked in. 
Kerosene ana crude oil penetrate so quickly that their application 
would only require an accurate sprinkler or distribution system. 
The application of dry chemicals should be as cheap and easy as the 
application of fertilizers. 
The prices of some of the chemicals used are extremely variable, 
sometimes as much as 50 per cent variation from one year to the next. 
Unless otherwise specified, the prices given below are those quoted 
in the General Schedule of Supplies of the United States Treasury 
Department, 1924. 
Cost of materials per acre for chemical treatments preventing wart 
Bichloride of mercury_ 
$5.75 for 2,500 grams. One-half gallon of 1 per cent solution 
per square foot. With 5 per cent of salt added to give better 
and more even distribution, the cost would be increased about 
$83.60 per acre, salt being 92 cents per hundredweight. 
Bordeaux mixture_ 
Copper sulphate 8 cents per pound, lime (estimated) 1 cent 
per pound 8-8-50, Yi gallon per square foot. 
Chloride of lime_ 
3 cents per pound, 1.6 pounds per square foot. 
Cleaning solution-- — 7 - 
Sodium chromate, 15 cents per pound. Sulphuric acid (sp. g. 
1.84), 36.8 cents per gallon (5.28 cents per kilo) 10 pounds sodium 
chromate, 3 gallons sulphuric acid, 12 gallons water, 1 gallon per 
square foot. 
$1, 896. 06 
313. 55 
2, 090. 88 
7, 550. 40 
