424 Diseases of Economic Plants 



or stem as a small, wart-likc protuberance. Badly rusted 

 leaves, or even whole plants, wither and die as though 

 blighted. In mild cases the leaves remain green and the 

 plant may bloom. 



It is reconmiended to sponge the diseased jiarts with 

 permanganate of potash: two tablespoonfuls of saturated 

 solution diluted with one quart of water. 



Leaf-spot [Cercospora althiiBna Sacc). — Upon the leaves 

 and other green parts of the hollyhock, velvet leaf, and mal- 

 low rather large, dark, angular spots are produced in abund- 

 ance, 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 decreasing 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. 



Leaf-spot {Phyllosticta 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. 



Anthracnose (Colletotrichum malvarum (B. & C.) South.). 

 — Since about 1885, this disease has been noticed in destruc- 

 tive form in greenhouses, particularly in the propagating 

 beds; in some cases to such serious extent as to nearly pro- 

 hibit commercial culture of the hollyhock. It occurs upon 

 any green part of the plant. On the leaves it forms brown 

 spots and causes withering; upon young succulent petioles or 

 stems, collapse of the parts beyond follows; if the parts be 

 older, sunken spots varying from light 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. 



Angular leaf-spot (Septoria) is also common. 



