DISEASES OF CULTIVATED PLANTS 343 
Another method, the formaldehyde or formalin drench, has 
proved successful for the control of AAzzoctonza in greenhouse soils. 
This consists in a solution of 40 percent formaldehyde in water, say 
at the rate of two to four pounds in 50gallons of water. ‘This is 
applied at the rate of one gallon per square foot of area and will 
involve a very severe wetting down of the bed and prevent immediate 
resetting of the soil owing to the persistence of the formaldehyde. 
One secondary effect of formaldehyde drench and lime in sandy 
soils in the forcing house was an increased yield of lettuce amounting 
from 60 to 90 percent over the ordinary crop. This was explained 
on the assumption that the parasitic fungus was destroyed and 
certain other inhibiting organisms at the same time. 
THE BEST FORCING HOUSE PRACTICE 
The best forcing house practice will contemplate a recurrent 
disinfection or sterilization of the soil during the idle period; it 
should be preceded by whatever applications of limestone and manure 
that are to be made tothe soil, then after thorough working and appli- 
cation of water to correct unevenness of moisture the soil may be 
sterilized by steam, or the formaldehyde drench be applied with 
assurance of results: obviously also this treatment must extend most 
vigorously to the plant beds and bring healthy seedlings to soil in 
which the soil parasites have been destroyed. 
‘The following tables of seed and soil treatments taken from the 
spray calendar will be of more use than extended description or 
discussion: 
