472 DISEASES OF ECONOMIC PLANTS 



upon the affected parts. Numerous greenish black, flat 

 sclerotia, 1-14^ mm. in diameter, are formed in the stems. 

 Dead leaf and stem remains should be removed from the 

 peonies before they are set in the ground. Bordeaux mix- 

 ture may be used after the plants appear in the spring. 

 Infected beds should be steamed. 



PINK 



Rust (Puccinia Arenarice (Schiim.) Schroet.). — This 

 rust was described in 1803 by Schumacher. It is quite 

 common upon various members of the pink family, as chick- 

 weeds, corn cockle, bouncing bet, etc. The sori are large 

 raised blisters arranged in characteristic concentric circles. 



piseased plants should be burned. 



PRIMROSE 



Phyllostictose {Phyllostida primulicola Desm.) . — Large, 

 circular, l^rown dead spots are produced upon the leaves. 

 Minute dark pycnidia may be seen. 



Ascochytose (Ascochyta primulce Trail). — Well-defined 

 oval spots, resembling those of phyllostictose, are formed. 

 These two diseases cannot be distinguished without the 

 aid of the microscope. 



Ramulariose (Ramularia primulce Thuem.). — In this 

 disease the blotches are yellow with centers of ashen 

 whiteness. No pycnidia are present, but instead a gray 

 coating of mold. 



CoUetotri chose (Colletotrichum primulce Halst.). — In this 

 blight the leaf as a whole is more involved than in the 

 above diseases, and definite spots are more rare. Dark 

 acervuli are present. 



