342 PLANT DISEASES 



BACTERIAL DISEASE OF TOMATO, EGG PLANT, 

 AND IRISH POTATO 



{Bacillus solanacearum, E. F. Smith) 



Dr. Erwin F. Smith has described in detail a bacterial 

 disease of the above-named plants in the United States. 

 Plants belonging to Physalis and Petunia were also proved 

 to be susceptible to the disease. The disease first causes 

 the foliage to wilt ; at a later stage the stem and branches 

 become discoloured and die. On cutting across a branch 

 in the early stage of the disease the woody cylinder shows 

 a brownish discoloration, and the vessels are filled with 

 bacteria, which ooze out at the cut surface in tiny dirty- 

 white or yellowish drops. 



In potatoes the disease passes down the stem and into 

 the tubers, causing a brown or black rot. 



In the egg plant (Solanum melongena) the symptoms are 

 similar to those in the tomato and potato. 



PREVENTIVE MEANS. The disease has been proved to 

 be transmitted by leaf-eating insects, the Colorado potato 

 beetle (Doryphora decemlineata) being used for experi- 

 menting on the potato ; consequently leaf-eating and leaf- 

 puncturing insects should be kept in check. Diseased 

 plants should be removed on the first indication of wilting. 

 Rotation of crops should be resorted to where the disease 

 has been present. 



Smith, E. F., U.S. Dept. of Agric., Bulletin No. 12, 



2 P l. 



LICHENES 



Ths larger foliaceous lichens are not parasitic; as to 

 whether the smaller crustaceous forms that appear to be 



