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SYMPTOMS. 



The dry rot here described is a strict tuber rot afifecting mature 

 tubers only. Neither the stems nor the young tubers are ordi- 

 narily in the least affected. Natural infection is known to occur 

 solely through wounds produced in the process of digging or sub- 

 sequent handling. In many cases this rot secured a foothold 

 through wounds produced by scab-producing animals of certain 

 sorts and perhaps even through scab spots due to fungus para- 

 sitism, though the latter method is certainly very rare if we 

 may judge from the laboratory experiments. 



The rotting is rather -slow, and in general within four to six 

 weeks from one-third to three-fourths of the tuber is destroyed. 

 The epidermis of the rotted portion becomes slightly wrinkled 

 and usually has a characteristic bluish color. On account of the 

 rapid destruction of the underlying tissues the surface over these 

 areas soon becomes distinctly depressed. 



The rot may make its appearance at any point on the surface 

 of the tuber, though more commonly perhaps at the bud end of 

 the tuber. There is no watery degeneration of the tuber unless 

 other organisms gain entrance, so that this is in fact a dry rot. 



CAUSE. 



Numerous inoculation experiments have shown that this dry rot 

 is caused by a parasitic fungus, not previously described, for 

 which we have proposed the name Fiisarium tuhcrivoruui. At 

 the same time it has also been demonstrated that this dry rot 

 fungus does not cause the injury to the leaves and stems often 

 referred to as "blight" or "wilt." In other words, the present dry 

 rot of the tuber is not connected in any manner with diseased 

 conditions of other parts of the plant. 



METHODS OF CONTROL. 



Extensive experiments have been conducted to learn if any 

 treatment might be applied before the potatoes were stored that 

 would reduce the amount of this rotting. 



These experiments have clearly demonstrated that dry rot may 

 be held in check through treatment of the tubers before being 

 placed in the storage cellars. For this purpose the best results 

 were secured through the use of either formalin dip, formalin 

 vapor, or the lime-sulphur wash. Not only did the tubers in 

 these lots show a very small percentage of dry rot, but they were 

 in excellent condition otherwise when removed in April. Ihe 

 storage time, it should be remembered, employed in this experi- 

 ment is longer than would ordinarily be employed by the average 

 farmer and this gave the treatments a severe test. Under ordi- 

 nary farm conditions the development of the formalin vapors is 



