366 
Journal of Agricultural Research 
Vol. XXX, No. 4 
SCOPE OF THE INVESTIGATION 
The experience of the average onion 
grower has led him to recognize that 
prompt and thorough drying or curing 
of the bulbs, and especially of the neck 
tissue, is the most practicable means of 
reducing neck-rot infection. In ordi¬ 
nary practice this condition is ap¬ 
proached by taking advantage of clear, 
bright weather and natural air cur¬ 
rents and by affording shelter during 
periods of rain or high humidity. 
However, it is not always possible to 
avoid the disease by these means. 
The purpose of the present investiga¬ 
tion has been to determine the effect of 
artificial drying of bulbs after harvest 
upon infection, and the feasibility of 
this as a practicable remedial measure. 
As a corollary to the above, a study was 
made of relation of maturity of tops 
and of the removal of the same at 
harvest time to the amount of infec¬ 
tion which occurs. All of the experi¬ 
ments reported, with one exception, 
were performed on onions grown in the 
Racine-Kenosha district of southeasten 
Wisconsin. 
EXPERIMENTAL RESULTS 
RELATION OF MATURITY OF BULBS TO 
INFECTION 
Methods of handling the onion crop 
vary in different localities. In some 
the bulbs are pulled and the tops 
clipped when the neck tissue is still 
quite succulent; in others, the tops 
are allowed to desiccate appreciably 
before they are removed; while in still 
others the tops remain attached for 
some weeks or months of storage. It 
is generally supposed that, other condi¬ 
tions being equal, the immature succu¬ 
lents necks are the most favorable for 
the beginnings of neck rot. Some ob¬ 
servations on this were made at Racine 
in 1917 and 1918. 
In each year a portion of a field of 
Red Globe onions was selected in which 
the plants were maturing unevenly. 
When the tops of the more advanced 
plants were thoroughly dried down, all 
of the bulbs were pulled and topped in 
the usual manner. They were then 
separated into two lots, which were 
designated “mature” and “immature” 
according to condition of the neck 
tissue. This was done on September 
17, 1917, and on September 16, 1918. 
In the latter year a portion of both 
mature and immature bulbs were 
clipped so as to leave about one-half 
inch of neck tissue, while in the re¬ 
maining portion 2 to 3 inches of neck 
was left. The bulbs were placed in 
1-bushel folding crates and, according 
to the customary practice, were then 
stacked in the field to cure for about 
three weeks. They were then removed 
to an onion warehouse for storage. 
The bulbs harvested in 1917 were 
finally examined on January 15, 1918; 
those harvested in 1918 were finally 
examined on March 8, 1919. The 
results are given in Table I. 
Table I.— Percentage of mycelial neck 
rot developing in bulbs harvested with 
“mature” and “ immature ” neck 
tissue; Red Globe variety , grown at 
Racine , Wis., 1917 and 1918 . 
Per cent 
Length 
Total 
of bulbs 
Year and con¬ 
of neck 
number 
in which 
dition of neck 
left 
Crate 
of 
neck rot 
tissue at harvest 
upon 
No. 
bulbs 
developed 
time 
top¬ 
in¬ 
in subse¬ 
ping 
cluded 
quent 
storage 
1917 
Inches 
Immature. 
1 
I i 
300 
300 
7 
6 
l 2 
Mature... 
1 
{ 3 
300 
300 
3 
3 
l 4 
1918 
| M 
/ 1 
88 
22 
Immature. 
\ 2 
/ 3 
1 4 
91 
90 
84 
23 
18 
23 
1 2 to 3 
| K 
/ 5 
163 
1 H 
Mature__ 
l 6 
206 
127 
165 
7 
1 2 to 3 
{ l 
9 
7 
i 
It is to be seen that in every case 
the percentage of neck rot in the 
immature bulbs was practically double 
that in the mature bulbs handled under 
identical conditions. The amount of 
neck tissue allowed to remain on the 
bulbs did not materially affect the 
extent of neck-rot infection, although 
the relative amounts of succulent 
tissue exposed is probably the im¬ 
portant factor involved. In confirma¬ 
tion of this the writer has data for 
1915 which show the Red Globe crop 
of onions in the Racine district was 
reduced from 20 to 50 per cent in 
storage by mycelial neck rot. The 
growing season of that year was un¬ 
usually cool and moist, and as a result 
the onions matured some four weeks 
later than usual and in most cases 
were harvested before the neck tissue 
was thoroughly dried out. Likewise 
in 1924, an unusually rainy season, the 
losses in all varieties of onion in this 
and in the Chicago district due to my¬ 
celial neck rot were as great as those in 
1915. As usual, the disease was most 
severe on the white varieties. 
