MAINE AGRICULTURAL EXPERIMENT STATION. 7 



disease." This, however, as it occurs in Maine, describes only 

 one phase of it. 



Everyone who prepares potatoes for the table is familiar 

 with the little black or brown spots which sometimes appear on 

 the tubers and which look like hard, superficial particles of 

 dirt which will not wash off. They are not dirt at all, but com- 

 pact masses of fungous threads, or the over- wintering stage of 

 a fungus which is as common as pebbles in New England 

 potato soils. Except that when it appears in quantity and thus 

 makes the surface of the tuber more or less unsightly I had 

 always felt that it was of no economic importance in New 

 England. Our recent experiences with this fungus as a cause 

 of disease of potatoes have led us to conclusions quite the 

 contrary. 



Soon after the potatoes are planted the fungus begins to 

 grow and, often in central and southern Maine, attacks the 

 young sprouts and kills them before they come up. The stalks, 

 however, 'may get some distance above ground before being 

 killed. Again, eases have been observed where fully 90 per 

 cent of the plants were attacked sufficiently to produce a prac- 

 tical failure of the crop so far as merchantable tubers were 

 concerned and very little evidence of disease could be seen by 

 looking at the tops. All through the season they appeared to 

 the average observer to be perfectly healthy above ground and 

 gave promise of an abundant harvest, but they suddenly died 

 when dry weather came on in August, when the tubers were 

 about half grown. In such cases it is a very insidious type of 

 disease. The fungus frequently attacks the underground, tuber- 

 bearing stolons, cutting them off after the young potatoes have 

 formed, or before they obtain much size, thus bringing about 

 the production of a large number of small potatoes in a hill; 

 hence the name, "little potato disease." 



There are a number of disease conditions, mainly character- 

 ized by the appearance of the parts of the plants above ground, 

 some of which are quite distinct while others appear to grade 

 into each other, and which are partly parasitic in nature and 

 partly of unknown origin. In Maine, with one exception, these 

 are by no means as common nor as destructive as they are in 

 the Middle West, Rocky Mountain and Pacific Coast states. 

 However, since those of a parasitic nature, and most of those 



