48 
COLOlfADO Plxrp:i;iMENT STATION 
{IS {IS 35 or 40 per cent smutted plants. The barley grains are 
replaced by a mass of black dust-like spores wbicb are the “seed” 
of the smut fungus. These are scattered about in threshing, some 
of them alighting on the surface of healthy grains of barley where 
they remain until the grain is planted. The smut spores germinate 
at the same time that the grain of barley 
germinates, and penetrates the tender 
seedling and grows up through the stem. 
At fruiting time the smut fungus grows 
out into the flowers and the developing 
kernel is replaced with a mass of black 
smut spores. 
Since the smut spores live over on the 
surface of the grain, the logical way to 
control the disease is to treat the seed with 
a disinfecting solution that will kill the 
spores witliout injurying the grain. A 
solution of formaldehyde in water has 
been found effective for this purpose. 
See directions for seed treatment in Part 
III. 
Loose Smut (Ustilago nuda) — Loose 
smut is common in Colorado but is not 
as destructive as covered smut, seldom 
causing more than 5% loss. Loose smut 
differs from covered smut in that the spore 
masses are not enclosed by a membrane 
but are borne loosely on the stem. Because of this fact the spores 
are scattered about by the wind as soon as they are formed which 
is just at the time that normal uninfected plants are blooming. 
Some of these smut spores fall upon the flowers of the blooming 
barley and grow directly into the developing grain. The grain 
hardens and becomes mature, however, before the fungus can form 
spores. The fungus is thus enclosed in a grain of barley that to all 
appearances is perfectly normal. When this grain germinates, the 
fungus also begins to grow and grows up through the stem replac- 
ing the developing kernels with a mass of loosely borne spores. 
Thus we see that the loose smut differs from the covei*ed smut also 
in the time and manner of infection. 
Because of the fact that the loose smut fungus lives over on the 
inside of the grain rather than on the surface the ordinary for- 
maldehyde treatment is not effective. A complicated hot water trc{it- 
Covered smut of Loose smut of 
barley barley 
