340 



The Spraying of Plants. 



Treatment. The trees should be sprayed with the Bordeaux 

 mixture as soon as the leaves appear, the application being re- 

 peated at intervals of two or three weeks until about the middle 

 of July. Clear fungicides should be applied to cherries early 

 in the season to avoid staining the fruit, and the same precau- 

 tion should be ob- 

 served with plums, 

 although the Bor-~ 

 deaux mixture may 

 be continued longer 

 with this crop. Four 

 applications should 

 be sufficient even in 

 very bad seasons; 

 and two or three 

 will generally be 

 found sufficient. 



Leaf Rust (Puc- 

 ci// id Pruni-spmo&& 1 

 Pers. ). Descrip- 

 tion. In general 

 appearance this dis- 

 ease is very similar 

 to the preceding. 

 The affected areas 

 are dull red upon 

 the upper surface of 

 the leaf and yellow- 

 ish-brown on the 

 lower surface, but 

 the spots are small, 

 and frequently 

 cause the foliage to 

 drop prematurely, 

 for the plum leaf 



FIG. 77. Black knot of plum. 



Give the same treatment as 



Treatment. 

 blight. 



Plum Knot ; Black Knot ; Plum Wart (Plownglitia [Sphcerid~\ 

 morbosa, Sacc.). Description. It is a common opinion that the 

 black knots (Fig. 77) found so generally upon plum and sour 

 cherry trees are caused by insects, but such is not the case. 



