a eee Te Te 
16 BULLETIN 1210, U. S. DEPARTMENT OF AGRICULTURE. 
effectual, and safe; and compared with copper sulphate was noninju- 
rious to the seed, but afforded no protection against reinfestation. 
Tubeuf (572, 374) states that laboratory experiments seemed to 
show that spores of T%lletia tritiet could be killed with an application 
of fe saa ldokode gas that would not injure seed wheat, but in field 
experiments as high as 15 per cent of smut occurred in the crop 
grown from seed thus treated. Damp grain was severely injured b 
the gas treatment. The use of gas, therefore, was not recommended. 
According to Tubeuf, a 12-hour treatment with a solution of 0.5 
er cent copper ouipuaie reduced the yield of both plants and heads. 
he injury caused by copper sulphate he reduced by an afterbath in 
milk of lime. Machine-threshed seed he found to be more susceptible 
to copper-sulphate injury than flail threshed. All grain treated with 
copper sulphate germinated better in earth or sand than in filter 
paper. Disinfection with hot water at 55° to 56° C. for 15 minutes 
resulted in complete freedom from bunt and no injury to seed, but 
he considered its use inconvenient. Seed which had been washed in 
water and subsequently immersed in a 0.1 per cent solution of for- 
maldehyde for a period of 4 hours, followed bs quick drying, showed 
no resultant injury. This treatment he found thoroughly effective 
in killing the smut spores, and he also proved Bordeaux mixture to 
be entirely effectual but likely to result in seed injury if the action is 
too prolonged. 
Tubeuf (574) gave attention to the effect of incrusting the seed 
with material containing (1) nutritive substances, such as Chile 
saltpeter, potassium salts, kainit, and superphosphate; and (2) toxic 
substances. 
Peacock (295), using copper sulphate at the rate of 1 pound to - 
4 gallons of water in an open tank from 5 to 10 minutes, obtained an 
average of 86.3 per cent germination and a bunt-free crop. A lot of 
seed resmutted after treating produced 4.5 per cent of bunted heads. 
Another lot, washed after treating and resmutted, produced 10 per 
cent of bunted heads, while an untreated check plat gave 35 per cent 
of bunt. 
Falke (108) found that injury from formaldehyde treatment is en- 
tirely prevented by rapid drying at 51° to 53°C. Volkart (384) pub- 
lished the results of a careful and comprehensive inquiry into the 
effects of the various treatments upon both the spores of bunt and 
those of oat smut, as well as upon the seed and the resulting harvest 
yield. Regarding the treatments with copper sulphate, the work 
showed conclusively that Tilletia spores were not killed in the ordinary 
methods of its use, hs only delayed or at best prevented from germi- 
nating, and that the viability of the spores could be restored by wash- 
ing in either dilute hydrochloric or acetic acid or by placing the spores — 
in the soil. He found for Tilletia, as Hecke ae ieaad for covered 
smut of barley, Ustilago hordei, that a reaction took place between 
the spores and the copper sulphate in which the copper ion united 
with some element of the epispore to form a compound insoluble in 
water, while the sulphate ion forms a soluble compound with some 
element or compound drawn from the spore. It follows from this 
that when a solution of copper sulphate 1s being used in farm prac- 
tice for treating wheat that contains a large amount of bunt it will © 
lose effectiveness much more rapidly than when the wheat is compar- — 
atively clean. It was found that the lethal effect of copper sulphate 
was increased by raising the temperature of the treating bath from 
