Second Report on Potato Culture. 6i 



present time another famine is threatening in Ireland and due to 

 the same cause. In our own country, while the disaster is not so 

 great, yet the loss this year has been enormous, and it is a loss which 

 might have been prevented. 



This disease in an aggravated form is not difficult to recognize, as 

 it may be perceived both by its appearance and disagreeable odor 

 which comes at first from the foliage and later from the decayed tubers. 



The fungus causing the common potato rot is an old offender. It 

 was undoubtedly introduced into Europe with some of the early 

 importations of the potato, and has in certain years proved so destruc- 

 tive that famines have resulted from the entire loss of the potato 

 crop. Such occurrences eventually lead to thorough study of the 

 organism. As early as 1846, the fungus causing the trouble w^as 

 very carefully described in an English publication,* and since that 

 time other observers have given the disease much attention. It has 

 spread to many regions in which potatoes aiC extensively grown, so 

 that both scientists and farmers are very familiar with many of its 

 characteristics. 



The most interesting feature connected with the fungus is 

 undoubtedly the wonderful energy which it exhibits, under favorable 

 conditions, in the destruction of the potato plants. It sometimes 

 spreads with such rapidity that a crop may be ruined in one or two 

 days; and unfavorable conditions, or the total destruction of the 

 plants, formerly appeared to be the only effectual agents in prevent- 

 ing or checking the spread of the dreaded disease. This rapid decay 

 of both the foliage and tubers is perhaps the most distinctive of 

 those characters which are commonly brought forward for the iden- 

 tification of the disease. It is almost invariably accompanied by a 

 strong, disagreeable odor which is easily recognized by all who have 

 once experienced it. When large fields have been attacked, the 

 ' smell is particularly strong; it then arises entirely from the foHage, 

 and is not produced by the tubers. 



The conditions which favor such rapid decay are, as a rule, not 

 generally present throughout this state. The fungus makes its most 

 rapid growth in a temperature of 70 degrees Farhenheit when much 

 moisture is present in the atmosphere. Cloudy days, with occa- 



Rev. M, J. Berkeley, JoHrnal of the Royal Horticultural Society, Vol. I. 



