12 DISEASE RESISTANCE OF POTATOES. 



The relation of the maturit}' of seed to its value has also received 

 considerable attention in Great Britain. Some of the best practical 

 potato growers prefer to have potatoes intended for seed dug before 

 they are fully mature, i. e., while the tops are still green and the outer 

 skin of the tuber rubs up easily. These tubers are then allowed to lie 

 on the ground a short time to " harden" in the light, i. e., to dry and 

 be slighth' sunburned, before they are put into storage. 



The practice of '"boxing" is common and very highly commended. 

 This consists of setting the tubers with "seed end'" up in shallow 

 boxes or trays in a dry, light room for some weeks before planting, so 

 as to have strong, short sprouts started upon them. In this way 

 quicker germination, stronger young plants, and a perfect stand are 

 secured. 



The general preference in Scotland and in England is for planting 

 small tubers, one and one-half to three ounces, planted whole. If 

 larger tubers are used they are cut, as in this countrj-. 



OBSERVATIONS ON POTATO DISEASES AND DISEASE RESISTANCE 



IN EUROPE. 



Insects cause the European potato grower little annoyance or loss 

 as compared with American conditions. Nowhere in Europe, so far 

 as learned, is any use whatever made of insecticides upon potatoes, 

 leaf-eating insects being practicalh" unknown. On the other hand, 

 diseases caused by fungi or bacteria or of nonparasitic origin are even 

 more common and destructive than in America. In the following 

 paragraphs is a discussion of the nature and relative seriousness of 

 such diseases as came under the Avriter's personal observation, coupled 

 in each case with the evidence secured as to disease resistance. The 

 less important and nonparasitic maladies are discussed lirst, reserving 

 until later the consideration of the late-blight and rot. 



CERTAIN MINOR DISEASES. 



INTERNAL BROWN SPOT. 



The peculiar disease of the potato called internal brown spot is as well 

 know^n to plant pathologists and practical potato specialists in Elurope 

 as in America. The writer learned nothing more about it on the Con- 

 tinent than is set forth by Frank," who reached onh" negative conclu- 

 sions. It is considered not to be a parasitic disease, and no remedy is 

 known and no suggestions are made except the doubtful one of aA'oid- 

 ing the use of diseased tubers for seed. . In England and Scotland 

 several potato specialists'' of wide experience gave evidence of like 



"Frank, A. B., Kampfbuch gegen die Schildlinge unserer Feldfriichte, "Bunt- 

 werden oder Eisenfleckigkeit," p. 211. 



6 Prof. J. H. Middleton. Messrs. Suttijn & Sons, and Thomas A. Scarlett. 



