SPRAY MATERIALS 145 



This quantity is sufficient for the fumigation of 1000 cubic 

 feet of space. The fumigation is used to destroy diseases on 

 certain crops when they are placed in storage. The potato 

 and onion are two crops often treated in this way. When 

 fumigation is practised the crops are placed in crates and 

 piled up in rows in a tight room. The gas is generated by 

 pouring the formalin in a flat-bottomed dish and adding the 

 potassium permanganate the last thing before leaving the 

 room. The room should be closed tightly and allowed to 

 remain closed from twenty-four to forty-eight hours. 



Seed Treatment. — The diseases of some of our crops are 

 found on the seed. In such crops, the treating of the seed 

 before planting it is very beneficial and greatly increases 

 the yield. The two common materials used for seed treat- 

 ment are formalin and corrosive sublimate. 



The formalin is more generally used and is more adapted to 

 a larger number of seed. The black leg of the cabbage and 

 the smut of the onion are two common diseases which can be 

 partially controlled by treating the seed with this solution. 



The scab of the potato is greatly reduced by soaking the 

 potato seed in a formalin solution made by placing 1 pint 

 of formalin in 30 gallons of water. The potato should remain 

 in this solution for about two hours. 



Corrosive sublimate is also used for the treatment of potato 

 seed. The corrosive sublimate should be used at the rate of 

 2 ounces to 16 gallons of water and the potatoes allowed to 

 soak one and one-half hours. 



The most recent work on seed treatment is a modification 

 of the cold method treatment. Recently the Iowa station has 

 modified this method by dipping the potatoes for two min- 

 utes in a hot formaldehyde solution and allowing them to 

 dry. They report the efficiency of this method has been 

 demonstrated in the laboratory and in the field. This is a 

 decided improvement over the old method, because a hot 

 solution is more active than a cold one and it has the advan- 

 tage of greater penetration and the ability to kill more 

 rapidly. It is more practical when a large quantity of seed 

 is treated, as it consumes very little time as compared with 

 .the cold method, 

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