368 
Journal of Agricultural Research 
Vol. XXX, No. 4 
was always a difference in favor of the 
untopped lots with the colored varieties. 
These are in the main so resistant to 
neck rot, however, that the importance 
of the difference is slight even though 
consistent. A striking comparison be¬ 
tween the resistance of colored and 
white varieties in 1920 is given. All 
lots were rained upon twice during 
curing, and environing conditions were 
thus quite favorable for the disease. 
In spite of this, the untopped colored 
varieties remained free from disease, 
while the topped bulbs showed slight 
amounts. With the White Globe 
variety heavy infection occurred and 
the difference between the topped and 
untopped lots was negligible. It ap¬ 
pears, therefore, that when favorable 
conditions for infection prevail, this 
variety may be expected to succumb 
regardless of the method of handling 
tops at harvest. On the other hand, 
some advantage may be expected 
with the colored varieties in an average 
season if the tops are left intact during 
storage. 
Table III.— The effect of removal of 
onion tops at harvest time upon the 
occurrence of mycelial neck rot; ex¬ 
periments conducted at Racine , Wis., 
1917-1920 
Percent¬ 
Year and 
variety 
Topped 
or un¬ 
topped 
Crate 
No. 
Total 
number 
of bulbs 
in¬ 
cluded 
age of 
bulbs 
affected 
by neck 
rot at end 
of storage 
period 
Per cent 
1 
271 
1 
. 
2 
234 
(°) 
(Untopped 
3 
207 
(°) 
1917 
1 
4 
219 
(°) 
■ 5 
233 
(«) 
Red Globe. __ 
6 
292 
5 
[Topped __ 
7 
295 
5 
8 
315 
6 
9 
326 
4 
1918 
(Untopped 
1 
2 
136 
156 
4 
2 
Red Globe... 
[Topped.. 
3 
4 
127 
165 
9 
7 
1920 
Red Globe.__ 
/Untopped 
(Topped.. 
1 
2 
365 
340 
0 
(«) 
Yellow Globe- 
/Untopped 
(Topped.. 
3 
4 
297 
323 
0 
6 
White Globe. 
fUntopped 
(Topped.. 
5 
6 
304 
338 
52 
56 
• Less than 1 per cent. 
INFLUENCE OF ARTIFICIAL CURING 
UPON INFECTION 
The evidence already presented has 
pointed to the importance of the con¬ 
dition of the neck tissue of the onion 
bulb when exposed to the fungus in 
determining the amount of neck-rot 
infection. These data, combined with 
general field observations, suggested 
the possibility that rapid artificial cur¬ 
ing of bulbs immediately after harvest 
might accomplish two things favorable 
to the control of neck rot. It would 
desiccate the neck tissues immediately 
so as to make them unfavorable for 
infection; and it would permit earlier 
removal to storage and thus facilitate 
better protection of the crop from 
inclement weather following harvest. 
Curing experiments were conducted 
in 1917 and the results have already 
been briefly reported. 6 Further experi¬ 
ments on a large scale were conducted 
in 1918, but conditions were so unfa¬ 
vorable for neck rot in that year that 
practically no disease developed even 
in the controls. Further experiments 
were run in 1923 with favorable re¬ 
sults. It is therefore considered advis¬ 
able to report the experiments of 1917 
and 1923 in some detail. 
A very simple arrangement for dry¬ 
ing was used in the 1917 experiments. 
A small room equipped with a coal 
heater was arranged so that the tem¬ 
perature could be raised to 100 or 
110° F. Air circulation was provided 
by raising a double window about 4 
inches from the bottom and lowering it. 
an equal amount from the top. The 
onions were placed in shallow layers in 
standard slatted crates used for storage 
of onion sets. These were so placed as 
to secure the maximum benefit from 
the circulating warmed air. It was not 
possible to keep a uniform temperature 
by this means. A continuous record of 
temperatures was kept, and in the 
tabulated data the total number of 
hours above 90° F. for any given period 
is stated. In 1923 a specially con¬ 
structed chamber was used, through 
which warmed air was forced by means 
of an electric blower. By the latter 
process the same amount of drying was 
secured in much less time. 
Experiments with onion sets.— 
Two lots of White Portugal onion sets 
were treated in 1917. The first of 
these (Lot I) was grown upon soil 
6 Walker, J. C. control of neck rot and anthracnose of onion sets. (Abstract) Phyto¬ 
pathology 8 : 70. 1918. 
