Second Repopi' on Potato Culture. 59 



others, and it may at times be confined to certain localities, yet with- 

 out doubt this is one of the enemies to the potato crop which must 

 hereafter be taken into consideration and remedial measures adopted 

 in order to insure the success of the potato crop. 



Two kinds of blight, designated respectively as early and late, prey 

 upon potato^, and as they differ essentially in their characteristics will 

 be described separately. 



Early Blight [Macrosporium solani). 



As the name indicates, this usually makes its appearance early in the 

 season and upon early varieties of potatoes. Hot, dry weather favors 

 its growth, and it is usually most severe in its attacks where the pota- 

 toes are planted on dry soils. It will, however, make its appearance 

 when the weather is moderately cool. Whenever the potato foliage 

 has been injured by the flea-beetles it seems to be predisposed to attacks 

 of the early blight, the spores finding a favorable resting spot on the 

 injured places of the leaf. Any condition or treatment which has pro- 

 duced a weakening of the plant causes it to be more likely to attacks 

 of blight. Strong, healthy, growing plants may be entirely free from 

 attack, while plants which have for any reason been checked in their 

 growth fall an easy prey to the disease. While this early blight does 

 not cause the potatoes to rot, it so injures the foliage that the growth 

 is checked long before maturity, and instead of the potatoes being full 

 grown they are undersized and immature. It is very possible for the 

 early blight to attack a field of potatoes and its presence never be 

 recognized by the farmer, it being mistaken for a. case of early matur- 

 ity. This may be the reason the early blight fails to attract as much 

 attention as the late blight, and it no doubt does far more damage 

 than is generally accredited to it. 



It is difficult to describe its characteristics definitely, as so many 

 variations occur, and as it frequently is confounded with the late blight, 

 it being sometimes scarcely possible to recognize the difference without 

 the aid of a glass. It usually makes its appearance during the latter 

 part of June or during July, and may even appear as late as August. 



The parts of the foliage first attacked are likely to be the edges of 

 the leaves, the disease manifesting itself in several places on the 

 same leaf, the affected area at first being circular in outline. The- 



