Family Solanaceae 321 



from getting a foothold in the United States. This 

 can be accomplished only by strict quarantine laws 

 prohibiting the importation of tubers from countries 

 where wart is prevalent. 



Melters or Leak 



Caused by Pythium de Baryanum Hesse; Rhizo- 

 pus nigricans Ehr. 



Melters is a common storage and shipping disease. 

 The trouble is prevalent in the Delta region of San 

 Joaquin River, California. The rot is common 

 during hot weather and begins to work soon after 

 harvesting. 



Symptoms. The disease first appears as small dis- 

 colorations at a cut or bruise made by an im- 

 plement at harvesting. The rot does not affect 

 unbruised tubers. Later the affected potatoes turn 

 brown, become soft (fig. 61 g), and if pressure is 

 applied a brownish watery liquid exudes, wetting the 

 neighboring tubers. 



The Organism. Orton 1 has shown that leak may 

 be induced by the fungus Rhizopus nigricans. For 

 a fuller description of this fungus, see soft rot of sweet 

 potatoes, p. 156. Hawkins 2 has further shown that 

 leak may also be caused by the fungus Pythium de 

 Baryanum. For a description of the latter, see also 

 damping off , p. 43. 



1 Orton, W. A., U. S. Dept. of Agr. Bur. PI. Ind. Circ. 23 : 1 1, 1909. 



2 Hawkins, L. A., U. S. Dept. Agr. Jour. Agr. Research, 7: 627-639, 

 1916. 



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