24 BULLETIN" 034, U. S. DEPARTMENT OF AGRICULTURE. 
seedlings (82) as well as for pines, to prevent by soil disinfection 
losses before the seedlings appear above the ground. Heat disinfec- 
tion of seed beds has been frequently mentioned. Burning wood 
or litter on the surface of the beds before sowing, said by Gilbert (47, 
p. 36) to be a common procedure in preparing tobacco seed beds both 
in Italy and in parts of this country, has been recommended for 
coniferous seed beds by Biittner (25). The disadvantageous results 
sometimes noticed following the application of wood ashes to pine 
seed beds may prove an objection to this type of treatment in some 
of the nurseries. At a Xebraska nursery (67) moist heat proved only 
partly satisfactory, unavoidable reinfection having serious results. 
Steam disinfection, using the inverted-pan method commonly advo- 
cated for tobacco seedlings (10, 47, 81), has been reported by Scott 
(123) as successful at a nursery in Kansas. Gifford (46) found 
steaming with the inverted pan only partly satisfactory. It is not 
believed that it is likely to pay to install the necessary apparatus for 
steam disinfection at nurseries in nonagricultural districts where 
steam tractors are not available for temporary use. The hot-water 
soil treatment as used by Byars and Gilbert (27) is probably worth 
a trial at any nursery where damping-off is serious and fuel cheap. 
It may be that in some localities where steam or hot-water treatment 
of the soil is not sufficiently effective, its efficienc} T can be increased 
by reinoculating the soil immediately after treatment with sapro- 
phytic molds and bacteria to provide maximum competition for 
parasites which come in from the outside. Tests of this procedure 
will be described later in the present bulletin. The value of char- 
coal has been emphasized by Retan (109, 110). 
Chemical disinfection of the soil has also been employed. Sulphur 
has long been in use as a soil treatment against the damping-off of 
various plants (45, 111) in addition to its use in combating potato 
scab and onion smut. It was tested on conifers by Spaulding (136, 
137) in the form of light surface applications to the beds after ger- 
mination, but without decisive result. In later cooperative tests pow- 
dered sulphur raked into the soil before the sowing of the seed failed 
to indicate any large measure of value. Very finely divided forms 
of sulphur in various amounts and times of application are prob- 
ably worth some further test. 
Moller (90) and Sherbakoff (128) have reported the successful use 
of copper sulphate in combating attacks of Corticium on dicotyle- 
dons. In Johnson's experiments on tobacco seedlings (82, table 
3) copper salts and Bordeaux mixture were the only chemicals for 
which any value was indicated. Sherbakoff apparently used copper 
sulphate and other strong disinfectants chiefly to stop the extension 
of vigorously spreading damping-off foci by local treatment rather 
than as a general treatment for use over the beds. Such treatment 
