
New York AGRICULTURAL EXPERIMENT STATION. 563 
soaking with some fungicide before they are planted. The same 
may be said of purchased seed of unknown origin. The cost of 
treating the seed is slight and the operation does not require 
much labor. 
The following preventive measures are also recommended: 
(1.) Select soil free from the scab fungus if possible. No treat- 
ment is known which will insure a crop of smooth tubers on 
infected soil. 
(2.) Plant only clean, smooth seed.* 
(3.) Scabby potatoes or scabby beets$ should be thoroughly 
cooked before being fed to stock in order to prevent the fungus 
, _ from being disseminated with the manure.§§ 

*In experiments conducted by Thaxter, scabby seed very greatly increased the 
number of diseased tubers produced. See Annual Rep. Conn. Exp. Station for 
1891, p. 157. See, also, Beckwith in report of this Station for 1887, p. 310. 
Bolley gives an excellent discussion of this point which leads to the following 
statement based on abundant experimental evidence: ‘‘ 3cabby or disease-bear- 
ing seed tubers can and will under ordinary circumstances produce a diseased 
crop.” See Bulletin No. 4, North Dakota Expt. Station, Dec., 1891. 
§ In the Bulletin just quoted Bolley states that potato scab also attacks the 
various varieties of beets. 
§$ Thaxter says he is convinced ‘‘ That the practice of feeding scabby tubers 
to stock is one of the most important means by which the disease is spread on 
farms. In view of the well-known fact that great numbers of fungus spores 
can and do pass through the digestive tract without injury, and that the scab 
4 fungus is known to grow luxuriantly in decoctions of horse or cow dung, it is 
‘ not unreasonable to assume that its spores, passing through the digestive tracts 
of stock fed with diseased potatoes, continue their development in the manure 
after evacuation.”’ See Annual Report Conn. Expt. Station for 1891, p. 158. 
Kinney states that ‘‘Stable manure scattered in the furrows at time of plant- 
ing is favorable to the development of the disease.”’ Bul. 14, Oct., 1891, Rhode 
Island Expt. Station. 
Ber. In. view of the nature of the disease Thaxter’s conclusion on this point seems 
better than the more positive statement just quoted. He says ‘‘ Barnyard 
manure which has not been contaminated by the scab fungus may not materi- 
ally increase the amount of scab.” 
Hexamer observed that under the exclusive use of commercial fertilizers scab 
almost entirely disappeared while under the exclusive use of barnyard manure 
the amount of scab increased. See American Agriculturist, Vol. LI, p. 172. 
Humphrey states that ‘‘ Potatoes raised on barnyard manure were markedly 
- more scabby and more deeply scahbed:than the rest.” See annual Rep. Mass. 
State Ex. Station for 1889, p. 219. 
Green finds that the use of barnyard manure as a potato fertilizer has increased 
ef potato scab. See Bulletin Ohio Expt. Station, Jan., 1899. 

the yield, but not always the total marketable product because of the prevalence 
