Alfalfa in Kansas. 



349 



causes considerable shattering. The disease is said to run its course in 

 the first crop and is not noticed 'again until the following year. 



No variety of alfalfa is resistant to it. The bacteria causing this 

 disease live over in the soil and gain entrance into those stems which 

 are cracked or split by late freezing. 



YELLOW TOP OF ALFALFA. Occasionally this trouble is found in fields 

 where unfavorable soil conditions exist. The disease is recognized, as 



the name indicates, by a yellowing of 

 the leaves. Generally this is most 

 noticeable at the tips. As far as 

 known, no parasitic organism is as- 

 sociated with its occurrence. The 

 disease is merely indicative of an un- 

 thrifty growth, brought about by un- 

 favorable growing conditions. 



STEM CRACKING OF ALFALFA. A 

 peculiar cracking or splitting of al- 

 falfa stems has been observed very 

 frequently in the first crop. These 

 splits may occur on any part of the 

 stem, and not infrequently two and 

 three cracks are found on a single 

 stem. (See Fig. 298.) They vary in 

 length from half an inch to two 

 inches and extend to the center of 

 the stem. As high as 15 per cent of 

 the stems in some fields have shown 

 this affliction. In itself this splitting 

 would not be serious, since the stems 

 do not wilt as a result, but the tissues 

 generally callous over sufficiently to 

 prevent this. These openings do form 

 a means of entrance for diseases, 

 however, and one species of fungus 

 in particular (Phomopsis, sp.) figures 

 materially in causing trouble when- 

 ever there is an injury. This fungus 

 develops rapidly after it has once 



gained entrance into the stem. It produces a blackened condition, caus- 

 ing the tissues to dry out. (See Fig. 287.) The weakened stems become 

 brittle and frequently lop over and wilt. The exact cause of the cracking 

 is unknown, but it appears to be related to extremely rapid growth 

 brought about by excessive moisture. 



Losses from these troubles can be prevented by mowing the crop as 

 soon as possible, and since it occurs mainly on the first crop, a little 

 earlier mowing may be advised. 



FIG. 295. Red or violet root rot in 

 later stage, showing the little projecting 

 knots of fungus, which are violet in 

 color. 



