ORNAMENTAL PLANTS 467 



Cercosporose (Cercospora althceina Sacc). — Upon the 

 leaves and other green parts of the hollyhock, velvet leaf, 

 and mallow rather large, dark, angular spots are produced 

 in abundance, each spot with a dark border and an ashen 

 center upon which numerous black hyphae may be seen. 

 Badly diseased leaves fall, and by midsummer only dead, 

 leafless stalks may remain. Even in mild cases, by de- 

 creasing the amount of green surface, the spots both injure 

 the appearance of the plant and lessen productiveness. 



Spraying with Bordeaux mixture or ammoniacal copper 

 carbonate at intervals of about ten days is thoroughly 

 effective. 



Phyllostictose (Phyllostida althceina Sacc). — This pest, 

 long known in Europe, is recognized as large, brown, 

 circular spots, 1-2 cm. or more in diameter, upon the 

 leaves. The centers are brittle and usually break away 

 irregularly. 



Colletotrichose, anthracnose (Colletotrichum Malvarum 

 (Br. & Casp.) South.). — Since about 1885, this disease has 

 been noticed in destructive form in greenhouses, particu- 

 larly in the propagating beds ; in some cases to such serious 

 extent as to nearly prohibit commercial culture of the 

 hollyhock. 



It occurs upon any green part of the plant. On the leaves 

 it forms brown spots and causes withering. When upon 

 young succulent petioles or stems, collapse of the parts be- 

 yond follows. If the parts be older, sunken spots varying 

 from Ught yellow to black are produced. 



The plants should be sprayed with Bordeaux mixture as 

 soon as the first leaves appear and every second day there- 

 after. 



