22 
COLOKADO ExPf:inMENT STATION 
They soon Avilt, die and become dry and brittle. In one-year-old 
plants the disease may extend into the crown and roots and killing 
the entire plant. 
The disease is caused by a bacterium which gains entrance into 
the plant through cracks caused by frost injury. For this reason 
the disease commonly affects only the first crop of alfalfa. It is 
most severe after late spring frosts. 
Frosted alfalfa should be clipped as soon as danger of further 
injury from frost is past. This rids the plant of the cracked stems 
by means of which the bacteria enter and permit the production of 
new healthy shoots. 
Leaf Spot (Pseudopezizza medicaginis) (2) — Leaf-spot is the most 
common and perhaps the most destructive of alfalfa diseases. It is 
widely distributed, occurring where ever alfalfa is grown. 
Leaf-spot of alfalfa. (Original in Bulletin 212 by Robbins.) 
