3o8 Journal of Agricultural Research voi. xm, no. 6 



New York, Ohio, Kentucky, Tennessee, Wisconsin, Minnesota, Iowa, 

 Kansas, South Dakota, California, Idaho, Oregon, and Washington. To 

 judge from the wide range of conditions under which the disease has 

 already been found, there appears to be no reason to doubt that it will 

 be found in practically all of the important well-established alfalfa- 

 growing regions in the country. It is possible that this leafblotch is not 

 yet introduced into some of the nevN^er and more isolated districts. 



Outside the United States the only record of its occurrence in America 

 is from Argentina (5). In Europe the disease has been found in Austria, 

 Germany, France, and Italy, where it has long been known, though not 

 regarded as important. 



ECONOMIC IMPORTANCE 



To what extent the yellow-leafblotch is a serious economic factor 

 in the culture of alfalfa it will be impossible to state with confidence 

 until a larger amount of data has been collected over a period of years; 

 but that it does produce large loss of foliage under certain conditions 

 is beyond doubt. From observations made largely at Madison, Wis., it 

 appears to vary widely in the severity of its attack on different cuttings 

 from the same field, depending largely on the abundance of infectious 

 material and on weather conditions favoring infection. Under favorable 

 conditions it has caused much larger loss of foliage than the leafspot 

 caused by the fungus Pseudopcziza medicaginis . For instance, when 

 the first crop was being cut on the experiment station farm at Madison, 

 on June 19, 191 6, it was estimated by observers that this disease had 

 destroyed about 25 per cent of the foliage, and that at least 75 per cent 

 of that remaining was more or less infected. In the summer of 191 5 

 the disease was twice reported in private correspondence to the writer 

 as of economic importance, by Dr. M. P. Henderson in the Rogue River 

 Valley, Oreg., and by Mr. L. E. Melchers in Kansas. In a recent report 

 {11) Melchers has stated that in many places in Kansas in 1916 the 

 disease caused a loss of 40 per cent of the foliage of the first and second 

 crops. 



Frequently only a small part of the diseased foliage falls off and is 

 lost. The fungus does not usually kill the invaded tissue until a large 

 part of the leaf has been penetrated; but invaded tissue easily becomes 

 water-soaked during rains, whereupon the leaf dies, and upon the return 

 of dry weather it quickly shrivels and falls. 



DESCRIPTION (PL. d) 



Although the disease varies considerably in appearance, it has charac- 

 teristics which make it easily distinguishable from other alfalfa diseases. 

 The first visible evidence of its presence on the leaf is usually a blotch 

 of characteristic yellow color, with its longer diameter parallel to the 



