Minnesota Plant Diseases. 



leaf and these spots often occur in sufficient numbers to con- 

 siderably damage the plant. The winter spores are two-celled. 



Spraying with dilute 

 bordeaux has been recom- 

 mended just as the buds 

 are opening and the leaves 

 are expanding, and at in- 

 tervals later. The fallen 

 leaves should be burned. 

 Apple scab [Vcntnria 

 ponri (Fr.) II 7 int.]. Ap- 

 ple scab is by far the most ^^K 

 serious disease of apples. 

 The fungus first appears 

 in early summer on the 

 leaves of the apple tree as 

 light, greyish, circular i-'m. isa. AI 



spots which spread rapidly, often combining with neighbor- 

 ing spots to cover large areas of the lent. The spots later 



turn olive green 

 and finally black. 

 The surface is 

 covered with up- 

 right threads 

 from which the 

 s u m m e r spores 

 arc thrown off. 

 These 1 spores rap- 

 ilv increase the 

 spread of the fun 

 gus from leaf to 

 leaf ami tree to 

 tree. The spots 

 are frequently sn 

 1 a r g e and nu- 

 merous that the 

 leaves b e c o m e 

 considerably distorted and are often shed. Whole trees may in 

 this way he stripped of their leaves. This sometimes happens un- 



n tin- fruit. Al'ti-r 



