1903.] PUBLIC DOCUMENT — No. 33. 35 



urally tend to aggravate a trouljle of this nature, but its 

 general and characteristic occurrence indicates the presence 

 of a more definite cause than this. Should the disease con- 

 tinue to prevail, care should be taken in starting new beds 

 to propagate only from healthy, vigorous plants. 



■Plum ''Yelloivs" 

 A disease apparently similar to the "yellows" of the 

 peach has been noticed for several years upon the college 

 grounds. It occurs only upon the Japanese varieties, par- 

 ticularl}^ the Abundance, and is as yet of no serious con- 

 sequence. The trouble is characterized by the production 

 of wiry yellow shoots, just as in the peach yellow^s. 



Spraying or Linden and Elm Trees for Leaf Spot. 

 Both of these shade trees are frequently affected with leaf- 

 spot fungi, which sometimes becomes quite abundant, causing 

 the leaves to fall prematurely. Some lindens on the college 

 grounds become badly affected each year with leaf spot 

 (^Cerco^pora microsora), while other nmcli younger trees 

 show little or no trace of it. The older, infected trees are 

 also more or less injured by borers, and many of the younger 

 trees show the effects of sun scald on their trunks. The 

 presence of the leaf spots on the older trees in such a])un- 

 dance is probably secondary, i.e., the trees are in such poor 

 condition they induce leaf spot to thrive. Elms are not so 

 badly affected with the leaf spot (Dothidella uhnect) as lindens 

 with the Cercospora. Some lindens and elms were sprayed 

 twice this summer, viz., July 12 and August 13. The result 

 of this spraying was very marked. The spraj^ed linden 

 trees could be easily identified by any one during September 

 and October, on account of the more abundant foliage and 

 greener color of the leaves. The foliage remained on the 

 sprayed trees some days longer than on the unsprayed 

 ones. While the sprayed trees w^ere affected to some ex- 

 tent with the spot fungus, there was a decided difference in 

 the amount of infection between the treated and untreated. 

 Better results would undoubtedly have been obtained if 



