337 



spots appear on the under side of the leaves and rapidly increase in size 

 and number thereafter until they cover the entire under surface. The 

 leaves then begin to curl ujjward and inward and similar patches of 

 jiowdery mold appear on the twigs. 



The damage from this disease results from interference with the 

 functioning of the leaves, and the injury done by the fungus causes early 

 defoliation and a marked stunting of diseased twigs. 



The history of powdery mildew on cherry in Illinois reaches back 

 to 1881, when it was found in McHenry, Rock Island, and Piatt counties 

 by A. B. Seymour. In 1883 Seymour found it in Adams and McLean 

 counties. It was reported in Ogle county in 1888 and 1890, in Kankakee 

 county in 189!), in Union county after 1880 by F. S. Earle, and in Cham- 

 paign county in 1893, 1897, 1911, and 1919. These early reports show 

 its occurrence in nine counties, eight of which lie within the northern 

 half of the state. 



As a result of the surveys made in 1921, 1923, and 192:1 powdery 

 mildew is now known to occur on the cherry in 65 counties as shown on 

 Map T5. These counties may be roughly divided into two groups, lying 

 respectively in the southern tip of the state and the northern half. Be- 

 tween these groups is a considerable area in which this disease has not 

 yet been found. 



Control of this disease is usually satisfactory if the ordinary lime- 

 sulfur spray schedule is followed. If special control measures become 

 necessary, it is best to use sulfur dust. Because powdery mildew is a 

 superficial disease, dusting is effective even when begun after it has made 

 its appearance. 



Brown Rot 



Caused by Sclcrotiiiin cinerca (Bon.) Schroet. 



The brown rot of cherry is the same as the brown rot of peach and 

 plum. In Illinois, however, the abundance of sweet cherries explains the 

 rare occurrence of the disease, since they are less susceptible to its attack 

 than sour cherries. 



It is known to occur in 1 4 counties, widely distributed over the state, 

 as shown on Map 7(!. It is somewhat the most common in southern 

 Illinois. 



Leaf Blight 



Caused by Coccoiuyccs liicmalis Higg. 



This leaf blight is similar to leaf blight of the i)lum and is caused 

 by a similar fungus. It is, in Ulindis, the most serious of the diseases to 

 which the cherry is subject. 



In late May or early June small, purplish, irregular or angular spots 

 appear on the leaves, which, when badly s])Otted, turn yellow and fall off. 

 Severe defoliation, which is by no means uncommon under Illinois con- 

 ditions, results in a serious weakening of the tree. 



