314 MAINE AGRICULTURAL EXPERIMENT STATION. 1907. 



was entirely prevented.* On the portion of the field which 

 had been under cultivation for many years, the amount of scab 

 varied in different parts as might be expected. While no 

 attempt was made to secure exact data on that part of the field 

 planted to alfalfa in 1904, there was a marked difference where 

 the fertilizer, lime, and ashes plots were located. Where com- 

 mercial fetrilizer was used very little scab resulted, somewhat 

 more was observed on the lime plots, while the potato crop 

 was badly scabbed where a heavy dressing of wood ashes were 

 applied when the alfalfa was planted 3 years "ago. 



WILL FORMALDEHYDE GAS INJURE THE SEED. 



In treating a disease like potato scab the following rule must 

 be taken into consideration. "The poison employed must be 

 sufficiently strong or concentrated to kill the parasite, but not 

 sufficiently powerful to injure the host." Five years of expe- 

 rience in treating potatoes with formaldehyde gas generated in 

 various ways indicate that, if properly handled, the gas from 

 3 pints of 40 per cent formaldehyde may be safely used to the 

 1000 cubic feet of space. In fact over 3 quarts to the 1000 

 cubic feet have been used repeatedly without injuring the ger- 

 minating qualities of the tubers in the least. 



However, the experience of one correspondent indicates that 

 the directions for gas disinfection as given in Bulletin No. 141 

 are deficient in that special attention was not called to the fact 

 that no potatoes should be placed directly over the generator. 

 The action of the potassium permanganate upon a part of the 

 formaldehyde generates considerable heat and makes the liquid 

 boil vigorously. It is this heat which vaporizes the liquid and 

 in a very short time sets free a large per cent of the available 

 gas in the solution. Hence, potatoes directly above the gen- 

 erator are exposed not only to considerable heat but to a gas 

 many times stronger and more active than they would be after 

 the gas became diffused and diluted with the air of the room. 

 The gentleman referred to placed his generator directly under- 

 neath and only a few inches below a large slat work bin in 



* Mr. Joel Remington of Monticello who treated his seed this season 

 with formaldehyde gas feels sure that by this means he prevented the 

 introduction of scab into his new ground. 



