PLANT-DISEASES. 69 



rust attacking, during summer, the leaves of various species 

 of poplar, including the cottonwood, balm of Gilead, etc. 



Bemedies. — Rake and burn the leaves. Spray with 

 copper compounds. 

 Potato. Early Blight. (Probably caused by 3Iacrosporium 

 Solani, E. & M.). — A blight of the foliage, appearing 

 rather early in the season, generally before August. The 

 leaves become yellowish and sickly and are marked with 

 small fungous patches. Progresses slowly. Does not 

 attack the tubers. Associated with flea-beetle attacks. 



Bemedij. — Bordeaux mixture. 

 PoTATO-RoT or Blight, Late Blight (PJujtophthora infes- 

 tans, De Bary). — The spores first germinate upon the 

 tops or vines, causing the foliage to become marked with 

 very large blotches, which generally cover a third or more 

 of the leaflet. Progresses rapidly. The disease soon 

 spreads to the tubers, causing discolored and diseased 

 potatoes. It is a " dry rot." The fungus may remain in 

 the tubers during winter. 



Preventives. — Plant on light or loamy, well-drained soil. 

 PJant only sound and disinfected tubers. Hill deep. 



Bemedy. — Spray the tops with Bordeaux mixture, or 

 other fungicide, upon the first indication of the blight, and 

 make three or more applications at intervals of ten days 

 or two weeks. 



The tubers should be stored in a cool and dry place. 

 Dusting them in the cellar with dry air-slaked lime is to be 

 recommended. Subjecting the tubers to a temperature of 

 105° to 110° for a few days will destroy the fungus and will 

 not injure the tubers for planting. 



There is another kind of potato blight and rot widely 

 distributed over the country, and probably due to a germ 

 or bacterium. The leaves curl, the plant droops and finally 

 dies, and the tubers contract a putrid rot. Very serious. 

 No remedy is known. Practise rotation. 

 Scab (Oospora scabies, Thax.). — Well-known scabby and 

 pitted roughness of potato tubers. The same fungus is 



