400 



1 l\(;ol S DISKASKS OK PLANTS 



), and it occurs also upon other species of this genus, 

 and upon some other related genera. Prior to 1 890 it had not been 

 noted in the United States, and it is doubtful if it was previously 

 common. Since that time, however, it has rapidly spread through- 

 out the regions where carnations are grown either under glass or 

 in the open. For a few years after its abundant appearance in this 

 country it threatened to cause a panic in carnation growing, and 

 florists' magazines and papers devoted much space to a discussion 

 of the disease, methods of control, susceptibility of varieties, etc. 



FIG. 197. CARNATION RUST 



It is now permanently established as one of the regularly antici- 

 pated diseases of the carnation, but there is no fear that its pres- 

 ence in any way jeopardizes carnation growing as an industry, at 

 least so far as the best growers are concerned. 



Host resistance. Since the appearance of this pest there has 

 been opportunity for selection, so that resistant varieties might 



cured, or at least so that the more susceptible sorts might 

 be discarded, particularly when more or less similar varieties 

 may be grown which are less sensitive. Perhaps no commercial 

 variety of this plant has proved more susceptible to the rust than 

 the Scott. The susceptibility of this variety seemed to be intensi- 



the longer it was in the trade. The Jubilee (scarlet) and 

 Flora Mill (white) have also proved susceptible, and these have 



