DISEASES OF CULTIVATED PLANTS 415 
Onion Smut, on the other hand, is prevalent to a considerable extent in Ohio. 
and is one of the most destructive of the smut fungi known to pathologists. 
This onion smut (Urocystis Cepulae Frost) unlike the other smuts with which we 
have to do, propagates itself almost indefinitely in the soil when this once becomes 
infested. Whenever a new crop of onions is grown from seed in this infested soil 
the smut attacks the young seedling onions, in whole or in part, and a very con- 
siderable loss results therefrom. If, however, onions sets are putin such soil, 
or seedling onions that have been started under glass in healthy soil are trans- 
planted to smut infected 
soil, the smut fungus 
cannot attackthem. The 
explanation seems to be 
that the smut threads 
areonly able to penetrate 
the leaves of the young, 
tender seedlings. This 
onion smut is now known 
tooccur in fields at Berea 
Perry, Madison and 
near Chillicothe. Atthe 
latter place it has seri- 
ously embarrassed some 
of the growers of onions 
for sets; for this work 
transplanting is, of 
course, out of the ques- 
tion. In Connecticut Ex- 
periment Station Report 
for 1889, it is stated that 
flowers of sulfur have 
been used to sow with 
the seed in infested 
soil, and this remedy 
has given but slightly 
inferior results to any 
other yet tried at this 
Station. Forty percent 
formaihyde, known com- 
mercially also as forma- 
lin, has given better re- Fig. 65. Sound and smutted onions, gathered in midsummer 
sults than sulfur in 1900. The healthy onions were grown on badly diseased soil by the use o¢ 
-At Berea, Chillicothe Formalin Drip treatment.—From a photograph by T. F. Manns. 
and latterly at Madison, 
experiments have been conducted to determine a practicable field method for 
smut prevention. The best method has proved to be that of formaldehyde drip 
with seeder. (See bulletin 131). The formaldehyde solution is made at the 
rate of one pound of 40% formaldehyde to 25 to 33 gallons of water. This is 
applied with drip attachment on seed drill at rate Oe ee ora per acre for 
field onions. The same results can be obtained i “dpet? furrows by applying 
solution with sprinkler after seeds are scattered until well moistened. This 
formalin treatment insures the disinfection of a layer of ‘soil near the seed and: 
permits the germination and the early growth, of the seedling onion, past infec- 
tion stage, before the smut fungus can again occupy this soil. Thegains from this 
treatment, both in the onion set work and in field onions are very large, amount- 
