230 PLANT DISEASES 



appear in the spring; the cups are grouped on conspicuous, 

 thickened, whitish spots on the stem and leaves. The 

 uredo stage follows under the form of minute brown spots, 

 often thickly scattered over the surface of the leaf. Finally, 

 the teleutospores are developed from midsummer to the 

 end of November as roundish or elongated spots on stem 

 and leaves. The uredospores germinate when mature, and 

 spread the disease, whereas the teleutospores germinate the 

 spring following their formation, and produce the first or 

 aecidium condition. 



Preventive Means. — Spraying with dilute Bordeaux 

 mixture arrests the spread of the disease. In dealing with 

 small quantities, as in gardens, spraying with potassium 

 permanganate or potassium sulphide effects the same 

 object. It must be remembered that the disease originates 

 in the spring from floating secondary spores produced by 

 germinating teleutospores that passed the winter on the 

 leaves or stems ; hence infected plants should be burned 

 as soon as the fruit is gathered, and not allowed to stand 

 or lie on the ground throughout the winter. In the case 

 of field crops these facts also apply, although it is difficult 

 to suggest a practical remedy ; but it is almost certain that 

 if the straw eventually finds its way to the manure-heap, 

 many of the teleutospores will survive until the manure is 

 used, and if this happens to be in a field sown with beans 

 or peas, infection of the crop will follow. 



Wild vetches should not be allowed to grow in hedges 

 or waste places. 



HARICOT BEAN RUST 



( Uromyces appendiculatus, Link.) 



Haricot beans or 'scarlet-runners ' are often much injured 

 by this pest. All three stages — aecidia, uredo, and teleuto- 



