16 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
and the plats with the thinner stands must have been very slight, this 
latter explanation has not much to support it. The data are believed 
to constitute further evidence of the importance of parasites in de- 
creasing the percentage of emergence in coniferous seed beds. That 
the effect of parasites on emergence should have been large enough 
in this case to make itself apparent on the face of the figures, despite 
the variations due to other sources, is especially interesting in view 
of the fact that the losses after emergence in these plats were not 
high. 
ECONOMIC IMPORTANCE OF DAMPING-OFF. 
The importance of damping-off in coniferous nurseries in Europe 
is indicated by frequent reference to the disease in the literature. 
Biittner (25, 26) states that whole beds are frequently destroyed by 
it. Baudisch (9) speaks of the death of entire stands in many 
nurseries as the result of damping-off. In the United States Spauld- 
ing (137) considers damping-off a serious obstacle in forest ation 
operations. Clinton (28, p. 318-349) reports serious damage to 
conifers in Xew England nurseries. The writer has found the dis- 
ease especially prevalent in nurseries in Xebraska and If ansas, a some- 
what unexpected situation in view of the relatively dry conditions 
prevailing there. A correspondent has reported heavy loss in seed 
beds in Texas. 
The economic importance of the disease in conifers is due in part 
to the rather heavy average losses experienced at many nurseries 
and in part to the irregular character of the losses. In one season 
losses may be negligible, while the next season the beds of certain 
species may be practically wiped out. Even without this element of 
uncertainty the losses experienced are expensive, because of the high 
cost of coniferous seed. The seed of some species costs from $3 to 
$5 a pound and seldom shows a germination of more than 60 per 
cent under nursery conditions. A loss of half of this 60 per cent from 
parasites, both before and after the seedlings break through the soil, 
is therefore a matter which deserves attention. The figures in 
column 8 of Table I, obtained by adding together those in columns 
6 and 7, show that the loss is frequently higher than this. At 
the nurseries at which control experiments have been conducted, the 
percentage of the seedlings in untreated beds which have been found 
by actual count damped-off after emergence is frequently more than 
50 per cent, in addition to the considerable but less accurately de- 
terminable loss indicated by the foregoing data as being caused by 
the parasites before the seedlings appear. 
It has been suggested by foresters and others that the net economic 
damage from damping-off is not as great as is indicated by the loss 
of seed and seedlings which it may cause. The argument is ad- 
