POTATO DISEASES AND THEIR REMEDIES. I7 



is almost coincident with that when the average potato grower 

 abandons his plants to weeds, insects and blights. The thrifty- 

 New England farmer is ashamed to have his neighbors see 

 weeds or bugs in his fields before this period, but, on the other 

 hand, he feels called upon to defend, if not to apologize for his 

 course, if later than this he pulls weeds, or sprays to protect his 

 plants. Yet the beginning of this vegetative period is the very 

 time when certain insects, notably flea-beetles and grasshoppers, 

 do their worst work ; and it is often serious work, indeed. If 

 a period of dry weather follows, and if the soil is either caked 

 or weedy, tip-burn is the inevitable result ; and when this begins 

 it is as a rule prophetic of the steady decline of the plant to its 

 death. Tip-burn is a physiological disease due to inadequate 

 water supply. The potato requires more water than do most 

 plants ; indeed, the production of a full crop demands that fully 

 one-fourth of all the water that falls on the soil during the entire 

 season shall be. absorbed by the plant, and either retained or cast 

 off through its leaves. Aloreover, the time of most active 

 demand for this water is at and shortly following this critical 

 period. The securing of this water supply is dependent upon 

 three things. First, the water-containing character of the soil, 

 determined by humus-content and thorough pulverization. 

 Second, surface tillage to conserve this. Third, healthy foliage 

 to carry on transpiration, which is the pumping process in plants. 

 Much of the so called " blight " of potato foliage is really tip- 

 burn, due to insufficient attention to one or all of these things. 



Starch manufacture is scarcely second to water supply in 

 importance for tuber formation ; this occurs entirely in the green 

 leaves under the invigorating influence of sunlight. The extent 

 of healthy leaf surface is, therefore, an exact index to the 

 capacity for starch formxation. When it is remembered that 

 one-half of the possible crop may be formed after the third week 

 in August, the importance of the preservation of the healthy 

 foliage through the early autumn becomes apparent. Certainly 

 the average potato grower has no just conception of his depend- 

 ence upon this late foliage for a full crop. As evidence of this 

 we are frequently asked by intelligent farmers whether there 

 is not danger of their plants "running to tops" as a result of 

 the spraying, and whether, in that case, they should not prune 



