Carnation Diseases 223 



Stigmonose 

 Caused by insect sting. 



Symptoms. The best symptoms of this disease 

 are manifested on the younger, but full-sized leaves 

 nearest the upper end of the stem. A casual glance 

 at such leaves reveals little to the untrained eye. 

 However, by holding them near the sunlight, small 

 dots may be seen scattered. These dots have a faint 

 yellowish color. Later the surface tissue dries and 

 the dots assume a whitish, reddish, or purplish 

 color, while the spots enlarge and become sunken 

 (fig. 46, g.). Such spots are seldom dark colored 

 in the center nor are they made up of concentric 

 rings. With the increase of the spots, the leaves 

 wither, but cling to the stems. The general effect 

 of stigmonose is a premature yellowing and stunt- 

 ing of the plant. The vigor of the plant at the time 

 of the appearance of the disease largely determines 

 the severity of the injury. Strong plants will be- 

 come spotted, but will in no other way greatly suffer 

 from it. Weak plants of the same variety will be- 

 come stunted, and in many cases seldom outgrow 

 the disease. 



The cause of the disease was first attributed by 

 Arthur and Bolley"^ to a bacterial organism BaC' 

 terium dianthi Arthur and Bolley. However, the 

 investigations of Woods t show that stigmonose is 



•Arthur, J. C, and Bolley, H. L., Indiana Agr. Expt. Sta. Bui. 

 59: 17-38, 1896. 



t Woods, A. F., U. S. Dept. of Agr. Div. of Veg. Pathl. and 

 Phys, Bui. 19: 7-30, 1900. 



