Alfalfa in Kansas. 339 



PLANT DISEASES AFFECTING ALFALFA. 



By L. E. MELCHERS, Department of Botany, Kansas State Agricultural College. 



The extent of damage caused by various plant diseases attacking al- 

 falfa in Kansas is generally not realized. At present no specific data 

 are at hand by which the writer can cite figures for the extent of injury 

 brought about by each different alfalfa disease, but from the plant- 

 disease survey records it is not difficult to see that the various diseases 

 listed below are found to a greater or less extent in all the alfalfa regions 

 of this state. Even basing the extent of damage at 1 per cent, which 

 would be very conservative, the combined loss from the nine diseases al- 

 ready known to occur in this state would amount to over $140,000 for 

 1914. 



Unfortunately the alfalfa crop is one in which its diseases can only be 

 partially combated that is, in preventing losses, from disease and this 

 only lies within the scope of the cultural methods of this crop. In other 

 words, spraying with fungicides would be impracticable; therefore, it 

 behooves the farmer at times to practice rotation, or cutting the hay 

 sometimes a little earlier than is ordinarily advisable, in order to prevent 

 the loss of foliage. 



Generally speaking, alfalfa diseases may be grouped into two classes: 

 (1) those caused by parasitic organisms (fungi or bacteria, and higher 

 types of plants like dodder), and (2) those which are nonparasitic (not 

 due to any known organism). 



Under the first group we have occurring in Kansas the alfalfa dodder, 

 leaf rust, three different leaf-spot diseases, the bacterial stem blight, the 

 red or violet root rot, the downy mildew, and a Phomopsis stem disease. 

 Other diseases attacking alfalfa which have not been reported in this 

 state thus far are the brown root rot, the crown wart and the root knot. 



Under the second group we have the stem-cracking disease and the 

 yellow-top disease of alfalfa. These are different maladies from those 

 before mentioned, in that they are nonparasitic that is, no organism or 

 germ is responsible for them. It will be seen that most of the alfalfa 

 diseases are caused by fungi, one by bacteria, and one by a higher type 

 of parasitic plant, namely, dodder. The fungi and bacteria which cause 

 the alfalfa diseases are very minute parasitic plants of a much lower 

 order than the dodder. In both cases, however, these parasitic plants live 

 upon or inside the tissues of the alfalfa plant, robbing it of its nourish- 

 ment, and thereby reducing its vitality. 



ALFALFA DODDER. A discussion of alfalfa dodder will be found under 

 the topic on weeds, for in fact it is a weed, producing a diseased condition 

 in the alfalfa plant. (See "Dodder," in index.) 



ALFALFA RUST (Uromyces striatus Schrcet). Although generally not 

 considered a serious disease of alfalfa, it did cause a slight amount of 

 damage in 1914, on the last crop in some localities. The extent of injury 

 varied from approximately one to three per cent, i. e., this percentage of 

 affected foliage dropped on account of the rust infection. 



