136 The Colorado Experiment Station 
beets, but the total yield of sugar was reduced 13.0 percent. The 
factory qualities of the beets were improved. 
A defoliation of from 50 to 94 percent depressed the yield of 
roots from 10 to 26 percent, the sugar in the roots from 0.5 to 2.7 
percent. A moderate defoliation reduced the yield of roots from 1.0 
to 14.4 percent. The percentage of sugar in the roots was not ma¬ 
terially affected. An injurious effect became noticeable in this case 
only when the beets developed a heavy foliag.e. 
Strohmer, Briem and Fallada, Jahresbericht der Zuckerfabrika- 
tion, 190.8, p. 33, experimented on the defoliation of beets to deter¬ 
mine the influence of the development of the beet at the time of 
defoliation upon the results. They claim that the effect in depress¬ 
ing the sugar in the beet depends upon the time that the defoliation 
is made. If it be made immediately prior to the period when the 
most active production of sugar takes place in the leaves the per¬ 
centage of sugar in the harvested beets will be depressed. If it be 
made long enough before this period to permit the beets to develop 
new leaves, the percentage of sugar in the beets may be as high as 
in normally grown beets, but the total yield of sugar will be less 
than that of normally grown beets or even of beets defoliated sub¬ 
sequent to the period of greatest sugar production (the end of Au¬ 
gust). Their results agree with those of earlier investigators in 
showing that a complete defoliation of the sugar beet depresses both 
the yield of beets and sugar and that a partial defoliation may pro¬ 
duce results in either direction. Their results show that defoliation 
on 12 July reduced the crop of roots by 37.0 percent and that of the 
sugar by 36.0 percent; defoliation on 30 July reduced the crop of 
beets 40.6 percent, that of sugar 43.3 percent; defoliation on 24 
Aug. reduced the crop 23.0 percent, the sugar 25.4 percent. 
The results obtained by defoliation is probably the best indica¬ 
tion that we have of the possible effects of the leaf-spot. It is true 
that the expression of “badly affected/’ “very badly affected,” etc., 
heretofore used in this bulletin do not give a definite measure of the 
extent of the defoliation, but it is the most feasible way of indicating 
it in our case. “Badly affected” would indicate that from 40 to 60 
percent of the foliage had been destroyed and “very badly affected” 
would indicate that upwards of 60 percent had been destroyed. This 
disease was so common and severe in 1910 that I doubt whether an 
attack involving less than 10 to 15 percent would have received any 
attention at all. We counted the leaves destroyed on a considerable 
number of beets and the number ranged from 35 to 43. The dam¬ 
age which was apparent varied with different beets, some having 
put forth a vigorous growth of leaves during August and early Sep¬ 
tember did not show the loss of this number of leaves, while others 
which had made a less vigorous growth of leaves subsequent to the 
