JODRNAL OF AGRICULTURAL RESEARCH 



DEPARTMENT OF AGRICULTURE 

 Vol. VI Washington, D. C, July 24, 1916 No. 17 



THE DISEASE OF POTATOES KNOWN AS "LEAK" 1 



By Lon A. Hawkins, 2 



Plant Physiologist, Drug-Plant, Poisonous-Plant, Physiological, and Fermentation 

 Investigations, Bureau of Plant Industry 



INTRODUCTION 



The tuber-rot of potatoes (Solanum tuberosum) known as the "potato 

 leak" is a disease of considerable importance in the delta region of the 

 San Joaquin River, Cal. The rot is manifest in hot weather and 

 appears soon after harvesting. As the potatoes in this region are sacked 

 in the field and are practically all shipped immediately, the disease is 

 therefore first evident in the car or warehouse. In extreme cases a 

 whole shipment may be so badly damaged as to be worthless. If only 

 a few "leakers" or "melters," as the rotten potatoes are called, are 

 present it is usually necessary to sort the consignment. The cost of 

 this sorting and the attendant shrinkage greatly increase the expense 

 of production. 



No exact data could be obtained as to the losses from this disease 

 for any given season, but various estimates placed the damage for 191 5 

 in the whole delta region, in which there were about 40,000 acres of 

 potatoes, between $50,000 and $150,000. The general conditions and the 

 methods of growing potatoes on these peat lands have been described 

 by Orton (n), 3 Irish (8), and Shear (15). Orton and Shear have con- 

 sidered the diseases commonly found on potatoes in that region. In 

 his paper Orton gives the results of a study of the potato leak, which is 

 the only investigation of the disease heretofore reported. He was, how- 

 ever, prevented from completing the work on this disease to his satisfac- 

 tion, and at his suggestion the writer took up the study. 



In the study of the leak of potatoes described in the present paper it 

 was planned to investigate further the causes of the disease, to study 

 the organism or organisms causing it, their mode of entrance into the 



1 The work described in this article was carried out as a part of the potato-disease project of the Office of 

 Cotton and Truck Disease Investigations. 



2 The writer's thanks are due Mr. W. V. Shear, of the Office of Horticultural and Pomological Invest 

 tions. for considerable assistance in the work at Stockton, Cal. 



3 Reference is made by number to "Literature cited," p. 639. 



Journal of Agricultural Research, Vol. VI, No. 17 



Dept. of Agriculture, Washington, D. C. July 24, 1916 



eq O—87 



(627) 



