Forage Crops 325 



side of the stem of the plant. The plants are at first 

 weak, the stems light colored, later discolored or black- 

 ened. Drops of thick fluid exude from the stems and dry 

 upon them, giving a glistening appearance as if they were 

 varnished. The chief damage is to the first cutting, though 

 in subsequent years the plants may die from decay of the 

 crown, or roots, or from loss of nutrition. Infection takes 

 place chiefly through rifts in the epidermis due to frost, 

 thereby affording access to wind-borne bacteria. 



Crown- wart ^^'^ (Urophlydis alfalfce (Lag.) Magn.). — 

 The chief diagnostic character is the presence of numerous 

 galls at or near the base of the stem. They vary greatly in 

 size from that of a pea to an orange. Diseased plants have 

 brown, dead stems, or stems that are weak and bear yellow 

 leaves. The disease apparently originated in South America, 

 is now widely distributed in Europe and was first noted in the 

 United States, in California, in 1909, later in Arizona, Oregon, 

 and Utah. 



Dodder ^^^ (Cuscuta sps.). — Dodder, or love vine, is a 

 parasitic, flowering plant. Its yellow, threadlike stems coil 

 closely around the alfalfa stems, and take nourishment from 

 them. It reproduces by seed, and the seed may readily pass 

 with alfalfa seed unless very carefully inspected. The 

 parasite is absolutely ruinous to the portions of the field 

 that it infests and, since it spreads rapidly, it is a serious 

 enemy. 



If dodder occurs in spots, these should be dug over or 

 burned over before it ripens its seed, using kerosene and 

 straw to insure heat suflEicient to kill every plant, with a 

 margin of a few feet entirely around the infested spot. 

 Badly infested fields should be plowed up. 



Minor diseases 



Root-rot, wilt {Fusarium sp.). — The first symptom of 

 this wilt is a yellowing of the outer leaves which gradually 

 spreads until all of the leaves and stems become discolored, 

 wilt, and die. This rot is said to be quite generally destruc- 



