194 DISEASES OF THE SWEET PEA 



the weight of the entire pan not being over 

 400 lb. The soil to be sterilized is pre- 

 pared as in the previous method, a few 

 potatoes being buried to gauge the amount 

 of heat produced. The steam is kept at 

 as high a pressure as possible, 80 to 100 

 lb. being best, for one to two hours accord- 

 ing to the pressure maintained. When 

 one section of the bed is treated, the pan 

 is lifted and carried to an unsterilized por- 

 tion and the operation is repeated until the 

 entire bed is steamed. 



(b) Formaldehyde. When steam ster- 

 ilization is not feasible because of the 

 absence of a steam boiler or for some other 

 reason, the formaldehyde treatment is the 

 next best. It will kill Thielavia, Fusar- 

 ium, Rhizoctonia, Pithyium, and Chaeto- 

 mium in infected soils. It is doubtful, 

 however, if it will entirely remove eel 

 worms from such soils. The formalde- 



