NOTES AND ABSTRACTS. 



139 



Thus exposure of the seed to formaldehyde gas is as effective as steeping 

 in formalin solution. A figure and description of the fumigating room is 

 given. The quantity of formaldehyde gas recommended was found not to 

 injure the eyes of the potato in any way except when the tubers were 

 placed very near the generating pan or immediately above it. Lime was 

 shown to increase the amount of scab materially thus : 



Treatment 1000 lb. lime 500 lb. lime No lime 



Per cent, of scab on potato crop 49 27 11 



F. J. C. 



Potato-Scab, Prevention of. By W. J. Morse (U.S.A. Exp. Stn. 

 Maine, Bull. 141 ; 1907). Potato scab due to the fungus Oospora scabies 

 is reported to be spreading. The scab fungus thrives best in an alkaline 

 soil, and is favoured by the application of stable manure, wood ashes, air 

 slaked or caustic lime, potash, lime and magnesia. It is more prevalent 

 in heavy, moist soils than in light, dry ones. When the soil is once 

 infected the danger of the disease attacking potatos placed in it remains 

 for many years. It is recommended to green manure such land as a partial 

 check upon the disease before attempting to grow potatos upon it. When 

 fresh soil is brought into cultivation care should be taken to. plant only 

 tubers free from scab, and these should be disinfected. The potatos may 

 be soaked for 2 hours in a solution of ^ pint of formalin in 15 gallons of 

 water, or in a solution made by dissolving 2 oz. of corrosive sublimate in 

 15 gallons of water for 1\ hour. The seed tubers may also be disinfected 

 by exposing them to formaldehyde gas in a close room for from 24 to 

 48 hours. The gas is generated by placing potassium permanganate in 

 wide, flat-bottomed tin or galvanized basins 8 inches in height, and 

 pouring over it formalin, closing the room at once. Twenty-three ounces 

 of potassium permanganate and 3 pints of formalin are required to 

 generate sufficient gas to fill 1000 cubic feet. — F. J. C. 



Potato Scab, Varieties Of. (Jour. Bd. Agr. xv. 10, January 1909 ; 

 pp. 749-751 ; 2 plates). — Scab in potato may be due to (1) mechanical 

 injury, due to the presence of ashes or sharp sand in the soil, or to 

 a season of drought ; (2) black scab due to the attacks of a fungus ; 

 (3) the attack of millipedes, especially Julus pulchelhis ; (4) the attack 

 of the fungus Oospora scabies, which produces a scab superficially 

 resembling that due to mechanical injury, but distinguished by the 

 presence of the parasite ; (5) the attack of the fungus Spongospora 

 scabies. — F. J. C. 



Potato Spraying 1 . By W. J. Morse (U.S.A. Exp. Stn. Maine, Bept. 

 1907, pp. 287-304). — Eelative results of spraying with standard Bordeaux 

 mixture against the leaf diseases caused by Phytophthora infestans and 

 Alternaria solani, as compared with dust sprays and spraying with 

 Bordeaux substitute are reported, the results being greatly in favour of 

 the Bordeaux mixture. Heavy and frequent spraying is shown to be 

 more beneficial than frequent light spraying with Bordeaux, owing pro- 

 bably to the better covering of the foliage by the former method. Spray- 

 ing is often ineffectual in Maine because the spray is imperfectly 

 distributed, the commencement of spraying is delayed too long, the 



