Minnesota Plant Diseases. 373 



Spraying- with bordeaux mixture or a solution of permangan- 

 ate of potash has been recommended. Diseased parts should be 

 immediately destroyed. 



The violet rust [Pnccinia violcc (Schiun.) DC.]. On all spe- 

 cies of our native violet can be found, often in considerable abund- 

 ance, this rust of violets. It also occurs on the cultivated violets 

 of greenhouses and may cause considerable damage. Cluster- 

 cups are formed on our wild violets, often in great abundance, in 

 the spring. Slight swellings of the leaf and distortion of af- 

 fected parts are usually caused, and the cluster cups occur on the 

 surface of the malformations. Later, summer and winter-spores 

 are formed, in small round patches, also, usually on the under 

 surface of the leaves. These do not usually show malformations 

 as in the case of the cluster cups. 



Infected plants or plant parts should be destroyed. 



The carnation rust [L'roinyccs caryophyllinns (Schrk.) 

 Schroet.]. On the leaves or stems of the carnation often appear 

 elongated, brownish patches, breaking through the epidermis and 

 exposing a more or less powdery mass of spores underneath. 

 These proceed from the mycelium, which lives in the stem and 

 leaves. The first spores produced are the summer spores and 

 these are light brown in color. They germinate immediately 

 after formation, and aid in spreading the disease. Later in the 

 season, darker, winter-spores are pnxluced and these pass the 

 winter before germinating. The mycelium, when once estab- 

 lished in a plant, remains there and forms pustules of spores in 

 succession. Diseased plants should not, therefore, be used for 

 cuttings, since the latter are sure to l>e infected. This disease has 

 proved very serious at times to carnation culture. 



Diseased plant parts should be cut out and destroyed to pre- 

 vent the spread. Bordeaux in fine spray at intervals of one to 

 three weeks has proven effective in checking the d 'souse. Potas- 

 sium sulphidf has also been recommended. The cultivation of 

 hardy varieties has l>een suggested and particular attention should 

 be paid to proper methods of cultivation, ventilation and watering. 



The sunflower rust (Pnccinia tanuccti IK'.}. This is one of 

 our most common rusts, occurring in great abundance on almost, 

 if not all. species of Helianthus and is particular' y abundant up- 

 on the common cultivated Helianthus animus. In addition, it 



