DAMPING-OFF IN FOREST NURSERIES. 23 
beds. Making the upper part of the bed to a depth of several inches of 
recently dug subsoil appeared effective in a single test by Spaulding 
(137) and at four nurseries by cooperators of the writer in later 
tests, the results of which will be published elsewhere. The procedure 
is unfortunately rather expensive in large-scale work and under some 
conditions at least undesirable because of the poor subsequent growth 
on such soil. Excessive vegetable matter (45), imperfectly rotted 
manure (67), or green manures recently plowed under (43) have all 
been advised against as likely to favor the disease. The experience 
reported with conifers (67, 139) indicates that damping-off can be 
to a certain extent decreased by broadcast sowing as compared with 
sowing in drills. The usual recommendation of thin sowing to avoid 
the seed-bed disease of other plants has also been made for conifers 
(67). Transplanting healthy seedlings from infected beds into new 
soil is recommended as a means of saving them from attack (11, 145). 
The writer's tests of transplanting at a Nebraska nursery gave no 
promise of economic value as a control method, although he is in- 
formed that it was successfully employed in a nursery in New Mex- 
ico. The time of sowing appears to have a relation to the amount of 
disease at some nurseries, but conditions in this regard evidently 
differ in different localities, so that' the best time to sow from the 
standpoint of avoiding damping-off must be determined separately 
by repeated tests at each nursery. For example, observations both 
by the nurserymen and the writer during several seasons at the 
Bessey Nursery, in Nebraska, indicate that fall sowing is an ex- 
cellent means of decreasing loss from damping-off in at least one 
pine species, and Ret an (110) reports the same thing for a nursery in 
Pennsylvania, while at two Kansas nurseries and at nurseries men- 
tioned by Tillotson (139) fall-sown beds suffer more than those 
sown in the spring. 
Treatment of the seed with mercuric chlorid (25) or with copper 
sulphate (122) has been recommended. While it has been demon- 
strated (38) that a proper heat treatment of the seed will greatly 
decrease the damping-off in sugar-beet seedlings, this is explained 
by the fact that one of the most important parasites of the sugar 
beet is systemic and often present in the seed. There is no reason 
to believe that seed-carried infection is of any importance in conif- 
erous seed beds. The only advantage that could reasonably be 
expected from a seed treatment of conifers would be that which 
would come from the prevention of seed decay in the soil before 
germination starts, and this protection could be expected to be ef- 
fective only if a relatively insoluble disinfectant, such as Bordeaux 
mixture, was used. 
Soil treatment is the most direct and probably the most profitable 
method of attack on the disease. It is especially easy, for tobacco 
