PLUM LEAF RUST 



251 



The fungus grows on tansy {Taiiacetum)^ and care should 

 be taken that this host is not allowed to harbour the para- 

 site in the neighbourhood of sunflowers. 



PLUM LEAF RUST 



{Picccinia primi, Pers.) 



This rust is very common on the leaves of cultivated 

 plum-trees, cherry, peach, apricot, and almond, and occurs 

 wherever these plants are cultivated. The aecidium stage 

 is absent. The uredo and puccinia stages form small 

 brown spots on the under surface of the leaves, and are 



Fig. 64. — Puccinia pruni. i, portion of a 

 diseased plum leaf; 2, teleutospore, x 300 ; 

 3, paraphysis accompanying teleutospores, 

 X300; 4, uredospore, x 300 ; 5, para- 

 physis accompanying uredospores, x 300. 



so abundant that they almost cover the entire surface. 

 The uredospores are globose, brown, and minutely warted. 

 The puccinia-spores or teleutospores consist of two super- 

 posed globose cells, the uppermost one usually largest, with 

 a deep constriction where the two join, clear brown, and 

 warted. 



When the leaves are attacked they fall early, consequently 

 the fruit is poor in quality, and the wood not sufficiently 

 hardened to resist frost. 



Preventive Means. — Spray with dilute Bordeaux 



