SECTION XLI. DISEASES OF IRISH AND 

 SWEET POTATOES 



The scab of Irish potatoes. Irish potatoes often have a 

 surface covered with rough scabs. This is a fungous dis- 

 ease. If a scabby potato is planted, both fungus and po- 

 tato are sown and the harvest will consist of both. More- 

 over, the fungus spores are apt to be present in a soil which 

 has recently produced scabby potatoes, ready to injure the 

 next crop of potatoes. Fortunately this disease is easily 

 prevented. A sound crop comes from smooth, healthy 

 potatoes in a soil where scabby potatoes have never grown. 

 For safety treat seed potatoes by soaking them two hours 

 in a formalin solution containing one ounce of formalin to 

 two gallons of water. 



The early blight. This is a common disease of the leaves 

 of the Irish potato. Round brown spots appear upon the 

 leaves, or irregular spots show on the margins. This dis- 

 ease is readily prevented by spraying the foliage with 

 Bordeaux mixture. Paris green may be added to the mix- 

 ture so as to poison the potato beetle at the same time. 



The soft-rot of sweet potatoes. Sweet potatoes in stor- 

 age are sometimes injured by the same little black mold 

 often found growing on bread or on preserves. When the 

 potatoes are stored where it is too moist and warm, this 

 fungus grows upon them and produces what is known as 



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