DISEASES OF CULTIVATED PLANTS 675 



212 Fahr., to be maintained for one hour or more. This applies 

 to high pressure boilers; for low pressure or hot water heating sys- 

 tems where the steam is applied in subdrains, four to five nours 

 steaming will be required with a pressure of six to seven pounds. 

 This treatment is effective for destruction of the eelworms or nema- 

 todes of cucumbers, violets and lettuce, the rot or drop fungus of 

 lettuce, the rosette fungus, and in general of all soil infesting para- 

 sites. 



Another method, the formaldehyde or formalin drench, has 

 proved successful for the control of Rhizoctonia in greenhouse soils. 

 This consists in a solution of 40 percent formaldehyde in water, 

 say at the rate of two to four pounds in 50 gallons of water. This is 

 applied at the rate of one gallon per square foot of area and will in- 

 volve 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 amount- 

 ing from 60 to 90 percent over the ordinary crop. This was ex- 

 plained 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 what- 

 ever applications of the limestone and manure that are to be made 

 to the soil, then after thorough working and application 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, (Ohio E. S. B. 214.) 



